Retrofit 24x reluctor to early V8

[Jim Blackwood]

Hey guys. Here's one that needs to be cleared up. Now I know lots of us have thought about adapting the '411 along with port injectors and COP to an earlier engine. Obviously the Gen 1 SBC comes to mind but although what will work for that will work for any of the GM v8's from that era and others besides, the specific aftermarket hardware available is not interchangeable. In my case a 1967 Buick 340. Same firing order as the early SBC and a few other similarities, nothing much to make it a difficult task once the injectors are in place. Before you ask, that's all done. The engine is in the car and ready to be started. If it would just start. So back to basics, starting with no spark.

Looking at the 24T tone wheel, in this case an OEM part bought new and mounted to the rear of the crank damper. Two things are needed with the wheel itself. First it has to have the correct side facing to the rear. Based on photos from the web it appears the two chevron shaped holes are to be towards the flywheel. Can anyone dispute this?

Next is the indexing relative to the VR sensor and to #1 TDC. This is where we run into trouble. After all these years 95% of the references simply say to use the fixture which only applies to the LS crankshaft. Very few even mention the actual alignment and among those there is no real clarity that I've seen. So I'm hoping we can answer this question in a situation where the fixture clearly cannot be used.

These things need to be verified:

1) The small round hole represents #1 TDC (zero reference) on the 24T tone wheel. According to the Holden document, the pulse pattern used does correspond to the teeth in the front half of the wheel going from that hole around in a counter clockwise direction. The teeth in the back half do not match the pattern at all. So far as I know, we as a collective have no idea how the logic of the two patterns is combined, other than to be combined in the sensor itself and come out on a single wire (the other two are +12v and ground according to the Holden document). We apparently do not know what that resulting pulse train looks like or how it is generated. If it matches the front plate what is the function of the rear one? The one thing I noticed is that the rear plate "closes up" the gaps in the front plate so that at each leading and trailing edge you get a short duration gap. If the VR sensor simply adds the pulses, then the rear ones would fill the gaps in the front ones and you end up with 48 individual negative pulses of perhaps a degree or so in duration irregularly spaced either about 3 or 12 degrees apart (numbers roughly based on Holden). In other words, every place the published pulse train shows an excursion going positive OR negative the actual signal would show a negative pulse. The resulting spacing looks like the following starting from but not including the zero pulse:
L-S-S-L-S-L-S-L-S-L-S-L-L-S-S-L-S-L-S-L-L-S-L-S-S-L-S-L-L-S-L-S-L-S-S-L-L-S-S-L-L-S-L-S-L-S-L-S There is likely some digital programming reason for this pattern.

Can anyone confirm any part of the above, particularly the location of the index hole at TDC?

2) Is there any built-in offset in the LS between the zero reference and the location of the VR sensor mounted in the block? In other words, with #1 at TDC is the sensor aligned with the hole in the tone ring or is it offset? If so, by how much and in what direction? This is required in order to know the correct position of the externally mounted sensor. To simplify, with the crank at TDC does the sensor line up with the small round hole, or is it offset? This needs to be confirmed by someone who has actually gotten it to run and checked time with a timing light, and/or by someone who has positioned the crank in the block and marked the tone ring through the sensor hole.

3) The VR sensor. Presumably it is installed with the connector opening facing forward, centered on the tone wheel and with minimum safe clearance. But this needs to be verified.

So. Is there someone out there who can say yea or nay with some authority?

Thanks,
Jim

[kur4o]

Look at this chart.chart (http://www.gearhead-efi.com/Fuel-Injection/attachment.php?attachmentid=14858&d=1575115794) this is how the signal looks like at the pcm. When you draw a line at the middle of the small hole on the reluctor wheel and you are at #1 tdc.

Pcm gets one signal of the wheel. It has 2 parts stamped due to very small 3 degrees openings. When they overlap you got solid piece resistant to damage.
I can only guess that at the center of the sensor the signal gets switched.

[Jim Blackwood]

That's the same chart shown in the Holden document I referred to above, just not as sharp. If you are saying #1 TDC corresponds with "0" on the chart I would tend to agree with you but that is still only one of several secondary questions. Even if true it does not answer whether or not there is any offset, which is the primary question.

Jim

[kur4o]

There isn`t any offsets. When the pcm reads position at 0 degrees the engine should have just reached #1 TDC. You can trace the slots on the reluctor and linked them to the chart. That way you will know exactly where #1 tdc is. You can wire the sensor to the pcm and measure when the signal is switched.

[Jim Blackwood]

Have you physically checked that by putting the crank to TDC and marking the tone ring through the sensor hole, then checking the mark to see if it lines up with the zero reference hole? If you have not, how have you verified that what you are saying is correct?

Jim

[kur4o]

You are over thinking it. The chart is not just some drawing. It is taken by an oscilloscope on a running engine and you have the absolute relation between reluctor wheel position and sensor at #1 TDC which equals to 0 degrees. There is no need to check it unless you don`t trust GM engineers and a scope chart. If there is any offsets how PCM interprets signal it is already there on the chart and there is no way you will know it. The small holes lines exactly with the slots on the wheel linked with the signal generated in the chart. That is how I know it. It is also used as a reference with the stock GM tool used to install the wheel.

Of course you turn the wheel any position if you keep the relations between #1 TDC, wheel position and crank sensor mounting position.

Now how the sensor aligns with the slots on the wheel is unknown and you have to verify it manually.

[Jim Blackwood]

Now how the sensor aligns with the slots on the wheel is unknown and you have to verify it manually.

I'm not sure what you are saying here but we could be in agreement for the most part.
I think there is very little chance that chart is an actual scope trace. Have you put a scope on it and checked it against a timing light in some way?(And have you ever seen a scope trace that clean?) I'm not entirely sure how you would even do that. How were you able to check the offset?

Go back and read my first post. It is very unlikely that the scope trace from that pickup would be anything but a series of 48 equal negative pulses unevenly spaced. Until someone actually puts a scope on it and checks it we have no basis to claim it is something else based on a published timing graph. Even if it is, that graph only tells us the pulse train beginning at the zero reference hole in the tone wheel. It does NOT tell us if that hole lines up with the pickup when the crank is at TDC. That is the information that is critical for installing an external crank trigger.

Jim

[kur4o]

It is very unlikely that the scope trace from that pickup would be anything but a series of 48 equal negative pulses unevenly spaced.

It is. 48/2=x24 full events the name says it all. I wouldn`t question official GM published data. No need to manually reinvent the wheel.

By looking at the width of the wheel and the sensor, I can guess the switching point is at the center of the sensor. The edge of the empty slot needs to get to the center of the sensor to trigger state change of the signal to the pcm. You will have to manually verify it.


Even if it is, that graph only tells us the pulse train beginning at the zero reference hole in the tone wheel

It says it. It have a degrees reference. 0 degrees always refers to #1 or #6TDC. 1 full rotation of crank is 360*. The signal at the scope chart represent crank rotation of 360* starting at 0 degrees or #1 TDC.

[kur4o]

Since it has been asked several times. Here is a real scope chart and it has the cam position also. Good luck with the project.
Now you have to need to confirm the switching point on the sensor.

[Jim Blackwood]

Thanks for posting that. Hard to argue against an actual scope trace. However as I said, the actual pulse train is a secondary concern. The primary and original question remains:

How did you verify that the zero reference hole actually lines up with the pickup when the crank is at TDC?

A reference line on a trace is just that, a reference line. Unless you have some way to generate a trigger from that line and then use it to trigger a timing light, and then use that timing light to flash on the damper or degree wheel and let you confirm that the timing mark lines up with the zero, then you haven't proven anything. Or it could be done by marking the tone wheel as I said before.

Has anyone done either of those things? Without that it is impossible to set up the external sensor position.

Jim

[dave w]

Attached is the data I have from my "Google Research" or "Personal Research".

dave w

[kur4o]

Forget about timing light tune up. What you need to do is mount the sensor to your preferred location. Bring the engine at #1 TDC. Rotate the wheel till the #1 tdc mark on the wheel is aligned with the sensor. Than you have your starting position for the wheel and very small adjustments will be needed from there.
Did you thought about the cam sensor. It must be aligned with crank too.

[Jim Blackwood]

As much as I appreciate the suggestions, you are avoiding the question.

Until this sensor/tone ring alignment question is answered it's nothing but recycling old web info that isn't on point. Simply assuming that the sensor lines up with the zero reference hole at TDC just isn't enough. Maybe it does, but maybe it doesn't. So far I have not heard from anyone who can actually confirm that it does. Based on my own testing results I'm inclined to think that maybe it does not, but again that is not definitive because failure to achieve an expected result does not disprove the existence of a relationship.

So, we are still at square one. Just so you know, I did align the sensor with the reference hole and there was no spark. This could be from other causes but the first step is to eliminate the obvious. Make sure the sensor is aligned properly so the ECM gets the right signal. At this point it is still not possible to do that.

Perchance in the next few weeks I can visit my machinist and he might have a LS block and crank and be willing to let me visually confirm the relationship. A few moments with a sharpie are all that are required. However, that again delays the operation. I was hoping someone here might be able to help.

Jim

[kur4o]

Make a drawing what exact measurements you need and I will try to get them in a day or two.

[dave w]

Forget about timing light tune up. What you need to do is mount the sensor to your preferred location. Bring the engine at #1 TDC. Rotate the wheel till the #1 tdc mark on the wheel is aligned with the sensor. Than you have your starting position for the wheel and very small adjustments will be needed from there.
Did you thought about the cam sensor. It must be aligned with crank too.

Good point on the Cam / Crank Alignment. My own personal research showed the 24x Cam / Crank Alignment is less sensitive than the 4x '0411 low resolution system. Pic below is from my R&D development of a low resolution dual trigger '0411 distributor (based on the L31 engine). The reason for 8 teeth on the dual trigger distributor is because 2 crank rotations = 1 cam rotation. Theoretically, a dual trigger distributor with 48x crank trigger to 1x cam trigger would provide coil on plug capability. Theoretically, a Large Cap HEI distributor diameter is needed to provide enough resolution for the 48x trigger wheel, pic below. I use CREO Elements Direct https://www.ptc.com/en/products/cad/elements-direct/modeling for my CAD drawings.

I think it's possible to CAD a Coil-On-Plug dual trigger distributor for virtually any domestic V8 engine manufactured after 1955 that used a distributor. Once the CAD is complete the CNC machine will do the rest of the work. Would it be practical .... that depends on the Budget. Would it be cool .... likely the answer is Yes

My 48x dual trigger distributor design would be based on the very successful aftermarket trigger wheel.

dave w

15140

15141

[kur4o]

I did align the sensor with the reference hole and there was no spark.

If the pcm gets the signal from the crank sensor, you will get spark but it will be at the wrong time. What is the distance from top of the sensor to the wheel. It must be really close. I have seen scored sensors by the wheel. Monitoring the pcm for rpm signal will show if it gets the signal. Troubleshooting the problem with timing light will not work. Get some logging device and monitor the PCM. If it sees rpm than you are good, if not the problem is within the sensor position.

[lionelhutz]

No spark at all means you've got something else wrong.

Match the pulses on the diagram to the notches in the wheel and you will find that the alignment hole matches with the TDC #1 pulse which means that is the TDC #1 position on the wheel. So, that's where the sensor MUST be when the #1 piston is also at TDC.

The scope traces also confirm that's exactly how it works because the cam signal switches at the same time the crank sensor picks up the #1 TDC notch beside the alignment hole. The alignment hole and corresponding notch must be passing in front of the sensor at #1 TDC for the sensor to be capable of picking it up.

When you hold a LS1 crank so the alignment hole is to the right, the #1 crank throw is facing where it'd be at TDC.

The crank sensor goes into the block with the plug facing forwards.

Tons of people have done this before and got it to work without the need to pursue the question you are so concerned about.

Centering the sensor at the alignment hole is plenty close enough to get your engine running. If you need it to be exactly accurate then tune it with no spark advance and fine adjust the crank sensor to get the spark at exactly TDC. That's assuming your crank sensor bracket is very solid yet has some adjustment and you also have TDC marked on the balancer with a pointer that has been verified with a piston stop.

Assuming you have the sensor clearance minimized, I would try moving the sensor forwards or backwards a little with respect to the wheel.

[Jim Blackwood]

Good suggestions but one step at a time is best I think. I will measure the sensor gap tomorrow. It's pretty close but I can close it up further if needed.

I agree with your thought that out of phase timing should not result in no spark. But as you say, a lack of a proper sensor signal would. I should be able to put a scope on the sensor and at least get a pulse train while cranking. Provided that looks usable I can move on to the low level coil output trigger signals. Those should be there as well.

As for a drawing as you asked, Here is how I propose to check the tone wheel and sensor alignment. It requires a block and crank with the pan off:

1) remove the CKS from the side of the block
2) rotate the crank to the zero timing mark, TDC
3) using a sharpie, mark the edge of the tone wheel by going in through the sensor hole in the block. This may require a shot of carb cleaner and an air blast first.
4) rotate the crank so that the timing hole is visible (pan removed)
5) locate the sharpie mark and note it's location relative to the timing mark. The accuracy with which the mark is made will affect this result.

That's it. A simple matter if a block is available, and it puts this discussion to bed. Once we know that is right I can get serious about the rest of the troubleshooting process. But for the sake of anyone working up a crank trigger for the 0411 controller this needs to be a known quantity. I actually hope it turns out to be zero as that means I have it right. But I really do have to know for sure.

Jim

[lionelhutz]

I'll suggest it again. Try the forward/backwards alignment of the sensor. The 24X sensor and wheel is a dual track system. The sensor reads each half of the wheel as a separate track. Hence, it must be aligned forwards/backwards correctly. Sensor rotation and direction are very important too.

The documents and the posted scope waveform provide more than enough info to get the sensor aligned with the wheel at TDC correctly.

[lionelhutz]

Post a picture if you can too.

[Jim Blackwood]

If it worked I'll have a shot of the damper below with a mirror showing the back side. If not I'll just have to try again.

Pretty sure the pickup is adequately located on-center. I'll measure the gap in a bit. I believe the pickup to be oriented the same way it is in the block, that is to say with the opening and pins facing the front of the car, despite it being on the other side. And perhaps with this visual it will make more sense what I am getting at here. Unless you have access to GM engineering drawings there is nothing in any chart or graph that is going to show the position of that pickup relative to the engine centerline, the crankshaft keyway, or the timing mark on the damper and even if there were it would be useless without the offset from the tone wheel timing hole and the pickup. But if anyone has access to those drawings by all means break 'em out and we'll get the inside scoop. Yeah, I didn't think so.

Well, let's see if this works. I've got email and such to catch up on and then I can get out to the shop.

I do appreciate the efforts to help, don't get me wrong about that. If any thing I post comes off harsh it's only because I've been around this kinda stuff for decades now and it's aggravating when it requires this kind of a roll-in-the-dirt brawl to make it behave. It was easier when I was younger. In the end I know it will be something simple but in the meantime I need to make sure everything I touch on while sorting it out is correct. We aren't past the tone wheel orientation yet. The rest comes after that.

Jim

OK, no photo yet. I'm working on it.

[brian617]

Unless you have access to GM engineering drawings there is nothing in any chart or graph that is going to show the position of that pickup relative to the engine centerline, the crankshaft keyway, or the timing mark on the damper

LS engines don't have keyways or timing marks on the balancer.

[dave w]

I have not tried using a factory 24x trigger wheel. I doubt it maters if the trigger wheel is factory or aftermaket. In my previous pictures, I hoped to show when the #1 cylinder is TDC of the compression stroke, the aftermarket trigger wheel is "Half Way" across the crank position sensor face. I adjust the sensor to 0.030" from the trigger wheel. The "pickup" inside the sensor is approximately 2mm, which is a tight tolerance to "center" the trigger wheel on.

A multimeter connected to the output of the crank sensor should show 12 volts to 0 volts as the trigger wheel is rotated by hand past the sensor.

dave w

[Jim Blackwood]

OK here's the trace below. If you look close enough you might be able to tell where the zero reference is on the pulse train but like I've been saying, without some way to compare that to TDC it's only helpful in showing that there is a usable signal going in at C1 pin 12 on the ECM. Anyone should be able to understand that zero on the pulse train does not mean zero on the crankshaft unless you match them up. They could be up to 180 degrees apart.

No key on the LS crank snout huh? Then how is the timing chain indexed? Maybe they deleted the mark on the balancer and the keyway in that as well, but you aren't normally going to mount an indicator to the #1 piston to find TDC on a serviceable engine so I suspect the aftermarket has corrected that little oversight.

Anyway as you can clearly see the signal is good, provided it starts and stops in the right place. Gap is .040" and centering is also within 1mm or less. I don't see a problem with any of that.

I can proceed to the outputs and check them and perhaps that will reveal the problem. BUT Until I can confirm that there is no offset between the index hole on the tone ring and the VR pickup (CKP) with the crank at TDC. this question has not been answered.

I do appreciate all the attempts to help. Dave, maybe I'm just too dense to see what you are trying to say. But your photos looked to me like what I've already seen on the web and I've not spotted the critical information yet. Just matching the pulse train zero to the indicator hole in the tone ring is not enough. We have that and have had it from the very start. What we do not have is the position of the VR sensor relative to the indicator hole when the crank is at TDC.

We keep going around and around the same old circle and we're not getting anywhere.

Jim

[brian617]

No key on the LS crank snout huh? Then how is the timing chain indexed?

The lower gear is keyed, however the balancer is not keyed, indexed or marked. Sorry about confusion.

[lionelhutz]

You are definitely being dense.

Forget about the damn locator hole.

The pulse pattern is WELL documented and the #1 TDC location is part of the pulse pattern documentation. There is nothing questionable about this pattern. It is completely known. Hell, the scope waveform even has the #1 ignition event you were ranting about needing to see.

You can easily match the wheel to the documented pulse pattern and find the spot on the wheel where TDC #1 occurs. I'm talking the teeth here, the falling edge of the 4th small tooth. Match the wheel to the pattern and find that tooth edge.

The sensor MUST be at that spot on the wheel when the #1 piston is at TDC. The sensor must be there to pick up and transmit the correct tooth edge at TDC. There is no magical delay or offset built into the sensor. The sensor switches immediately each time a tooth edge passes by it.

The other mistake is putting the wheel on backwards. Hold the wheel with the locator hole at 4 o-clock and the 2 chevrons at 3 o-clock and 9 o-clock. When you hold the wheel that way, the side facing you goes towards the back of the engine. You scope pattern is already correct so the wheel must be turning the right direction.

Start looking somewhere else.

[Jim Blackwood]

I'm just going to overlook the rudeness, and I hope you guys will bear in mind that even though you are probably well known and respected here I don't know you. I have no doubt you are fully aware of the amount of BS that gets passed off as fact on the forums so let's just try to be civil, what do you say?

Now if it were an LS everything you say would undoubtedly be true. But have you ever mis-timed a distributor? What I'm asking for is nothing more or less than which spark plug lead you line the rotor up with when you sock it in the hole. No difference whatsoever. It can be right, and it can be wrong. If it's wrong it won't run. It's just that simple. It's a physical relationship that cannot be determined electrically.

Despite the ranting, nobody so far has yet told me that he has in fact confirmed the relationship between the sensor and the timing ring. You've all tried every possible way you could think of to show that it isn't necessary and maybe it's possible to do that. I do appreciate the efforts. This last description comes the closest but is still less than crystal clear. I will elaborate.

>You can easily match the wheel to the documented pulse pattern and find the spot on the wheel where TDC #1 occurs. I'm talking the teeth here, the falling >edge of the 4th small tooth. Match the wheel to the pattern and find that tooth edge.

By saying "4th small tooth I take it you mean the 4th of a series of 5 which is in line with the "Damn locator hole" (your words)

>The sensor MUST be at that spot on the wheel when the #1 piston is at TDC. The sensor must be there to pick up and transmit the correct tooth edge at >TDC. There is no magical delay or offset built into the sensor. The sensor switches immediately each time a tooth edge passes by it.

Assuming you are correct my tone wheel is mounted and aligned properly. But to accept that at this point requires a series of assumptions which is never a good thing.

assumption 1) the zero marking in the pulse train represents TDC even though it is not marked as TDC on any document that I have seen yet. Have you?

assumption 2) There is no delay in the controller which is contrary to common practice. Every controller that I have seen or worked with has a delay built in to allow for timing advances to be made. For instance the EDIS-8 has the timing wheel advanced 6 teeth for a 60 degree interval between the indicated TDC and actual physical TDC. This allows the ignition module to advance the timing which is obviously required. Aftermarket ignition modules and engine controllers typically operate in the same way. I'm not saying that's the only way to do it, just that it is the most common convention, which means that assuming it operates differently is a kinda big ask. So it should be proven.

So the question remains. How is it that you know for sure that the #1 cylinder is at TDC when the sensor picks up that falling edge of the 4th tooth which is adjacent to the timing hole? Just because everybody knows that? I'm sorry but it just isn't good enough. There has to be more. That's not when the #1 plug fires. It's not when the #1 injector lights off. I'm not sure there is any signal coming out of the controller that exactly corresponds with that point in crankshaft rotation, so how can you prove that this relationship is true? Even if it is I doubt it can be proven without the engine running, except by physical inspection like I described.

So call me dense if you want but it's more accurate to say persistent. Or insistent. The thing that I am asking for has not yet been clearly demonstrated.

Personally I'm inclined to think it must be so. But so far as I am aware of, there is no place on the web that is has been actually shown. I'd love to be proven wrong on this but it really looks to me like it will take an actual physical check to do it.

Jim

[brian617]

Since it has been asked several times. Here is a real scope chart and it has the cam position also. Good luck with the project.
Now you have to need to confirm the switching point on the sensor.

Right here is your answer. With proper scope skills one can determine TDC with a scope. There are even programs out there that you can overlay all four cycles over a pattern to see the events in order.

[brian617]

http://productforum.autorepairdata.com/forum/showthread.php?t=12970

[lionelhutz]

Proof that #1 is beside the alignment hole.
#1. The pulse pattern is known.
#2. The Holden? document is marked from 0-360 degrees, which would be one crankshaft rotation from #1TDC to #1TDC.
#3. It is well known that the 1X cam signal switches between high and low each time the #1 cylinder passes TDC and two different scope traces were posted that shows the cam and crank signals with the cam signal switch lining up with the tooth edge that everyone calls #1 TDC.
#4. One of the scope traces also shows the #1 ignition happening before the #1 tooth edge gets to the sensor which helps confirm the alignment.

It doesn't matter at all what the PCM does internally with the signals. All that matters is that the sensor sends the #1 TDC signal to the PCM at the right time, using the well established 24x pattern.

People have had their engine run with the wheel both backwards and misaligned. You are getting the signal from the sensor. If you have the crank signal but no ignition then it must be something else.

Finally, you are posting rather blunt to ignorant comments about people not reading what you are asking and having to prove the already known to you so what do you expect in return?

[Jim Blackwood]

Fair enough, I think we need to put this on hold and move on. I will revisit it once I have a chance to do a physical inspection, probably in a few weeks. I'd encourage anyone else who has the chance to also do so. As I said, I'm just as willing to see the results go either way and would in fact favor your viewpoint as it means less work for me. I just want it resolved. I know you think... well, let's not go there right now.

Anyway, the next step is to set the cam sensor pulse to match the CKP sensor. It will be a wasted effort if I have to change the position of the tone ring but I suppose it's a chance I will have to take. After that I will look at the coil logic outputs. I agree, those should be there regardless of the timing and regardless of the cam sensor for that matter. (It and the coils are presently unplugged.) This should point me to the actual problem.

How about this, if I can get it to run and the timing light either does or does not match the advance map we should be able to claim we've proven the case one way or the other. Sound reasonable? (This engine DOES have timing marks.)

Jim

[dave w]

The measurements I have for the L31 Cam Position Sensor Flag is 175 degrees "Flag in Sensor" and 185 degrees "Flag out of Sensor".

My daily driver has a L31 engine with an aftermarket 24x Coil-on-Plug Conversion, using the original L31 distributor Cam Position Sensor.

Sensors will trigger on Leading Edge / Trailing Edge of the trigger wheel or sensor flag. The center line of the sensor is the critical alignment point for the trigger wheel or sensor flag.

GEN III computers have a CASE Learn Procedure for "Timing", mostly for production tolerance reasons. GEN III computers will "Assume" near perfect alignment of the CKP / CMP sensors, because that's the methodology of mass production.

It can be a challenging question: is success re-engineering the factory mass production methodology, or reverse engineering the factory mass production methodology. Either method will yield success, with measurements, alignments, and parts fabrication as good as the factory mass production tolerances.

dave w

[Jim Blackwood]

In this case the CMP sensor is mounted to a specially built oil pump drive unit which includes the flag for the sensor. It is essentially a cut down distributor which due to space constraints is in a much smaller package. Since I did not have those measurements it is 180/180 but hopefully that will be close enough. Once I get out to the shop I will backprobe the signal lead at the ECM, run a trace, and then rotate the body of the sensor to get the right alignment, or as close as I can get it given the 5 degree difference. I could probably trim the flag to match your specs but it would require some work with a die grinder. I'll see what the trace looks like first. Given considerations like the sensor lobe pattern, target distance, and overlap, that 180 degree mechanical configuration could certainly result in either a 175 or 185 degree pulse. I'll just have to measure it.

Sorry, no photo available at the moment.

Jim

[lionelhutz]

Don't align the cam sensor to the crank wheel. Align it to TDC. The signal should transition low to high at TDC #6 and transition high to low at TDC #1. With a meter you should be very able to set it up and test it for accuracy.

On a similar note, the engine will start without the cam sensor, just might need more cranking or a couple of tries to get it going.

[lionelhutz]

A true 1X cam signal is 180*. Look at the posted scope probes and it's clear the cam signal transitions at each full single turn of the crank.

The distributor Dave used was not from a 24X application, but apparently the PCM can cope with the variance of that sensor.

[Jim Blackwood]

Don't align the cam sensor to the crank wheel. Align it to TDC.

Should be the same thing right? I'll be using my scope and get a dynamic reading while cranking. I'm headed that way.

Jim

[dave w]

I opted to build a 1x distributor, non GM application.

dave w

15151

15152

15153

[lionelhutz]

Put a meter on the cam sensor and measure it as you crank the engine past TDC then you'll know it transitions at the right time.

[lionelhutz]

I opted to build a 1x distributor, non GM application.

dave w

15151

15152

15153

You make some of the coolest parts Dave. The fabrication you do is always impressive.

[Jim Blackwood]

CMP sensor and oil pump drive for Buick.

Jim

[dave w]

CMP sensor and oil pump drive for Buick.

Jim

Cool design:thumbsup:

The 1x distributor pictured in post #37 is for the low resolution 4x '0411 system.

dave w

[lionelhutz]

That will work.

Before I meant to use the meter and hand turn the engine past TDC so you can capture exactly when it transitions compared to the timing marks.

[Jim Blackwood]

After reviewing I think you guys are right. The #1 coil secondary trace on the joecar screen print was something I should have looked at more closely. Sorry bout that.

Anyway, I worked up a rudimentary bench mockup for the crank trigger and am working on getting a proper scope reading on that before I go back out. Photo below. It runs at 200rpm so is about right for cranking speed. Once I get that going and have consistent results with the scope I'll feel a lot more confident about what I'm seeing in the shop.

Jim

[Jim Blackwood]

Here's an interesting wrinkle. It appears that below a certain rotational speed the VR signal becomes unreliable. This makes perfect sense if you think about it since it relies on a somewhat similar triggering method as the scope does, which is to say, triggering a voltage state change from 0 to 12v and back depending on the transition of the signal generated by the tooth. The output signal remains a 12v square wave and this tells us that there is indeed signal processing going on in the sensor. It is not a simple VR pickup. If it were the voltage and waveform would vary with the speed and it does not, at least to any significant degree. This further tells us that the pickup probably uses the rear pattern to blank out noise or unwanted pulses from the 24 tooth wheel on the front.

BUT that also means that detecting the condition changes using a multimeter and turning the crankshaft by hand is likely to prove unreliable or at least inconsistent.

I see this on the mockup. Giving it a moderately slow spin through 1/4 of the rotation gives a good solid pulse train but I can slowly rotate it through any number of teeth at about the speed you'd be able to do with a wrench on the crankshaft without any voltage change at all.

I've not tested the cam sensor yet to see if it acts in a similar way.

Jim

[brian617]

This may sound super silly, but are you 100% sure the sensor connector is wired correctly?

0411 PCM?

Terminal (A) at connector (drkblu/wht) goes to PCM terminal (12) signal

Terminal (B) at connector (ylw/blk) goes to PCM terminal (21) low ref

Terminal (C) at connector (lt/grn) goes to PCM terminal (2) high ref

All PCM connector C1

[kur4o]

There is indeed some processing inside the sensor. I found this interesting chart for a 98 ls1. An inside schematics of the sensors. I also measured the cam/crank inputs of the pcm. They are grounded, so you need to feed some voltage to the pcm to sense signal. There is also more processing in the pcm. The signal is filtered and converted to 0-5v by a special chip before it goes to the TPU. So the square shape might not be that important unless some thresholds are reached.

The crank sensor being some sort of magentic pickup will be really sensitive on magnetized engine parts and paints on the wheel.
I have been thinking about the dual pattern of the wheel. Could it be that the 2 wheels are some mirrored image 180* apart, making the the wheel to be installed backwards for reverse rotation engine.

Best way to test for valid crank signal is to bench wire the pcm and log rpms while rotating the wheel. For most of the pcms anything under 50rpm is hardly picked.

[lionelhutz]

That makes sense for the crank sensor,

I was recommending testing the cam sensor by hand rotating. It picks up the 1x ring immediately with power applied and that lets the PCM know which 180* the crank is rotating once it starts to pick up the crank signal. Otherwise, the engine might have to crank a whole rotation before the PCM even knew how to start the engine. That's why it will still run without the cam signal, the PCM will eventually try both and get it running.

[Jim Blackwood]

Since I did get a pulse train on the CKP sensor lead (C1-12) that must wired the right way. Not so sure on the cam sensor. Apparently GM used different pin arrangements for both but I think the ones I have match the pinouts used here. Whether it matches the pickup could be a different matter I expect. I get a constant 7v output. I went out and found a couple more of my cam pickups, one uses a Ford sensor and the other is 2001 Silverado which matches the sensor on the car so I'm using that one to test. It seems unlikely that I would have 2 bad (new) cam sensors. The vehicle schematic shows a 12v input.

The CKP uses a VR sensor as the pickup then adds the signal processing to it. These type pickups are very common and are essentially an AC generator. You can pretty much tell that is what it is by the operating characteristics. The cam sensor uses a Hall effect sensor, which should be capable of switching at zero rpm. So it should indicate condition as on or off as soon as power is applied. These are commonly used in aftermarket ignition systems.

I'm working on getting a signal out of the cam sensor.

The large one below is the one I'm using for testing. The smaller one is pretty much configured the same as the old Buick V6 unit but uses the Ford pickup. It outputs a single short pulse so is not the right piece for the 0411 controller.

Jim

[Jim Blackwood]

Looks like part of the problem might be what I'm using for a cam sensor since this one wasn't used in 2001 apparently I will have to see if I can find the paperwork on that. However I tried every possible combination of power, ground and signal out hooking it up and could get no switching output so I'm starting to wonder if it provides a sinking output. Maybe I should try a pull up resistor next. Or a different sensor.

[dave w]

I'm sure we all know that the trigger wheel / flag material needs to made from a metal that is magnetic. Stainless steel is not magnetic enough. The surrounding material to the sensor needs to be non-magnetic.

dave w

[Jim Blackwood]

Right. I think I must have a bad sensor. Either that or I need a better bench test setup. I'm using the front mounted LS sensor.

Jim

[In-Tech]

The front mount cam sensor(LS3) is the best cam/crank sensor(non encoded 24x) there is. No pullup resistor required and is also non directional, meaning the mounting tab can be anywhere. It is pinned different than the LS1 cam sensor so please note that. I don't have that info in front of me but can get it tomorrow if you need.

[Jim Blackwood]

Thanks Carl. I think what would be most helpful would be a good wiring diagram for a bench testing setup for the cam sensor. Been looking for something on youtube but haven't found it yet.

Jim

[kur4o]

What type of pcm you have.

Also I think that 7v volts output is acceptable. The input of 12v is only a feed to the sensor and is processed so the output is likely lower.

[Jim Blackwood]

Yes, I hooked up the cmp and ckp leads to the 0411 ECM bench simulator to test. Good feed voltage, right at 12v, good low reference, 0 ohms to ground, about 5.5v out of the signal lead from the CMP sensor dropping a tenth or two when connected to the ECM.

No change with a relatively heavy steel target against the sensor. Looks like the sensor is bad. I'll order another one. Could be the one in the car is bad too. I heard there has been a rash of bad sensors, not necessarily GM but across the board. Ordered the Delphi part for the '05 Corvette.
Jim

[kur4o]

I just made a visual inspection about the sensor position in the block vs the reluctor wheel. The mounting tab of the sensor is facing to the front of engine parallel to the block. The sensor is really close to the wheel, I didn`t have a feeler gauge to measure. #1 TDC does seems to line up with the small hole. Now the interesting part. There are 4 tabs on the sensor 90* each. There is small gap between the 2 parts of the wheel. One of the tab is perfectly centered in the gap between the 2 parts of the wheels. If you draw a line from at the center of the wheel the sensor should be in that line straight. So it is perpendicular to the center of the wheel

I will get you a schematics of the 0411 later. I will try to see what is the normal voltage output. If it is not switching it is likely a bad one.

[In-Tech]

Hi Jim,
Yes to the bad sensors, just fought one on the dyno, brand new ac delco had intermittent output, never seen that before, usually works or it doesn't.

GM spec for gap is .020" - .040"

LS1 Cam
A=Signal
B=Ground
C=12v

LS3 Cam
A=5v
B=Ground
C=Signal

LS1 Crank
A=Signal
B=Ground
C=12v

LS3 Crank
A=Signal
B=Ground
C=5v Sometimes requires a 1k pullup

>>>>>>>>>>>>>>>>>>>>>>>>>>>

Ls1 MAP
A=Ground
B=Signal
C=5v

LS3 Bosch MAP
A=5v
B=Ground
C=Signal

[kur4o]

Some good reading for troubleshooting and a schematics for 0411 pcm.

[Jim Blackwood]

Here's a new scope trace, showing the CKP output and pin C2-26 output (coil 1 logic level) on the bench simulator. It'll be a couple weeks before I can add a third trace for the CMP sensor in the same screen shot, but this one shows that coil 1 at least is firing off, provided the wires and coils are good. That gives me something to look at while waiting for the new CMP sensor to come in.

Jim

[kur4o]

Cranking without cmp is hit or miss until the correct sequence is detected. The spark will be either correct or 360* off. After that it runs strong.

[Jim Blackwood]

Here's the cranking trace with no cmp. Shows #1 coil output. The trace doesn't always look like that, the first half varies from start to start. But what is apparent is that the ECM settles on a pattern. If the engine hasn't started by then it's 50/50 whether it will or not from what I can see.

Jim

[Jim Blackwood]

Kur4o, that was good information about sensor alignment. To restate, chevrons on the wheel to the rear (D shaped hole to the front) sensor connector facing forwards in line with the crank, aligned to the crank centerline (not off axis, note the tab is at an angle) wheel edge at the center of the sensor side to side, and in line with the index hole with #1 piston at TDC. Is this all correct, and have I missed anything?

Now on the CMP sensor, In-Tech I see that you show an LS1 sensor at 12v and an LS3 sensor at 5v. So my question is, what happens if you put 12v on the 5v sensor? That could possibly account for my failures. And since RockAuto doesn't list the sensors by LS1 or LS3 engine it would be easy to get the wrong one if you aren't ordering for a specific vehicle. I suspect I ordered the first two for the Silverado. LS3 right? The last one that I just ordered was for the Corvette, so LS1? To further confuse the question, both the Camaro and the Silverado use the same pin (C2-39) to feed the CMP sensor, but the 0411 with the Camaro OS feeds 12v to the sensor. Did they offer both the LS3 and the LS1 in the Camaro? Don't know if the Corvette is different or not. So the voltage change could be in hardware or software.

I will try the ones I have on 5v to see if it works.

Well, that does fit with my general methodology: Try every wrong way first, but a little more consistency would have been helpful.

Jim

Edit: My 2001 Silverado ECM also outputs 12v on pin 39 of C2. Just to further confuse things. Oh, but that used the rear sensor so that probably makes sense.

[brian617]

LS1 5.7L (car)
LS3 6.0L (car)
LM7 5.3L (truck)

I can get you the cam connector pin locations for the 0411 truck if needed.

[kur4o]

The voltage of the sensor depends by the pcm used. If you put 12v to a 5v sensor it will be fried.
The ls1 style PCMs are 12v, 2005 corvette ls2 and all ls3 and 6.2l engine use the 5 volts sensor. SO anything pre 05 will work for you, later depends on the engine type and pcm used.

The info for the sensor position seems correct. I am planning to take some shaddy pics and measure the gap between sensor and wheel too.

[In-Tech]

Hi Jim, I'm not sure my terminology is correct using "open collector" but the GM sensors(and the honeywell ones I have used) don't care if they are fed 5v or 12v. Sometimes, it appears the 5v sensor only outputs 5v so you have to use a pullup 1k resistor on the power and signal line to "boost" the signal output. I should have checked that deeper when I did it using a Mefi controller that will do 24x or 58x(flag settings and some other stuff) and whenever we used that controller on an LS3 we always had to use a pullup on the crank sensor.

I call LS1 cam any that are in the rear of the block(truck or car). I call LS3 cam any that are in the timing cover(truck or car). The early LS2 had the cam sensor in the timing cover and that's the only one I am not sure of as I think they are unique but have little experience with them and think those were all E40 computers, so again, not sure on those. I posted those voltages as that was what was on my notes so don't get too excited about that, lol.
-Carl

p.s. the cars and trucks use all the same sensors meaning if I need a crank or cam sensor for an LS1(24x, 1x, I order one for a 2001 truck and it is the same sensor as used in that year camaro/firebird/vette. When I want LS3(58x 60-2, 4x, stuff I just order for a 2011 Truck and it is the same sensors as Camaro/Vette etc
Hope that helps

[Jim Blackwood]

OK, thanks for the clarification. The Corvette sensor I ordered matched the reference number in Matt's EFI book for the front sensor so I'll check it out when it arrives. The one I have on the simulator also checks bad with 5v. I did not expect 12v would hurt a 5v automotive device. Most solid state devices I've dealt with seem to have a breakdown voltage at least 2 or 3 times the operating voltage. But it's the current that kills them.

Anyway, got the 2nd Perytech scope add-on for the laptop today (DSO U2200) but so far haven't been able to get the 3rd and 4th trace so I'm working on that. Hope to upgrade the drive on the sensor wheel to get a cmp flag tomorrow too. I've got a 4 tooth geneva wheel that I'm thinking about using. That'd be pretty sci-fi-ish but should work. I'd like to increase the speed range also but probably don't have too many options for that. Once it all works I may clean up a few rough edges, maybe add some more sensors too. Maybe the cmp sensor will get here tomorrow.

Jim

[Jim Blackwood]

This is too much even for coincidence.
The new sensor came in today. Immediately I set up to test it on the 5v source for EGR (C1-48) from the ECM (pin C), ground (C1-61)(pin B) and signal (C1-73) (pin A). No voltage change on pin A with the flag using a pair of medium sized unplated channellock pliers as the target. Changed to the 12v lead from the ECM (C2-39). Flag gives change from 3.31 to 3.23V out. With the signal line disconnected it is 341 and 3.33.

Three different sensors ordered at three different times from 2 sources and they all test bad in the same way? I'm at a loss here. Anybody got any idea?

It's the tan sensor for the timing cover. Controller is 12200411, OS is Camaro.

Jim

[dave w]

My L31 Vortec 5.7 Liter 24x / '0411 system uses the stock 1999 K1500 5.7 liter CKP sensor and stock 1999 K1500 5.7 liter CMP sensor. For my L31 Vortec 5.7 liter 24x / '0411 conversion, I started with a stock 2002 DBC LS1 Flash and tuned from there.

dave w

[In-Tech]

This is too much even for coincidence.
The new sensor came in today. Immediately I set up to test it on the 5v source for EGR (C1-48) from the ECM (pin C), ground (C1-61)(pin B) and signal (C1-73) (pin A). No voltage change on pin A with the flag using a pair of medium sized unplated channellock pliers as the target. Changed to the 12v lead from the ECM (C2-39). Flag gives change from 3.31 to 3.23V out. With the signal line disconnected it is 341 and 3.33.

Three different sensors ordered at three different times from 2 sources and they all test bad in the same way? I'm at a loss here. Anybody got any idea?

It's the tan sensor for the timing cover. Controller is 12200411, OS is Camaro.

Jim

GM spec for gap is .020" - .040"

LS1 Cam
A=Signal
B=Ground
C=12v

LS3 Cam
A=5v
B=Ground
C=Signal

LS1 Crank
A=Signal
B=Ground
C=12v

LS3 Crank
A=Signal
B=Ground
C=5v Sometimes requires a 1k pullup

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

Your wiring to THAT LS3 cam sensor is wrong, it is still wired like a LS1 cam. Easy fix and usually won't damage the sensor. Also you might grab power from pin B2 instead. Attached is a nice pinout chart for that ecm if you already don't have this one.

[Jim Blackwood]

OH HO! Here we go!

Connecting cmp pin A to a 5v source, in this case C1-48, pin B to sensor low C1-61, and pin C to sensor signal C1-73. I get switching at 4.45v flagged and 0.01v open. FINALLY, results. So, does the other sensor work? No it does not.

Switching to 12v gives a 10.9v signal return.

First check in the car will be to reverse pins C2-39 and C2-73 at the ECM and see if I get a return. Maybe I'll get lucky and that sensor will be OK, and just need to be aligned with the crank sensor.

Jim

[In-Tech]

Cool,looks like you are on your way. I was just reading back through a little and it's humorous how posts can be so vague and I apologize, I didn't mean to as I wasn't clear enough in what I was thinking especially on the voltage. Also I will verify my thoughts sometime. As far the 24x crank sensor, yes it is designed for a split wheel, so is the LS1 cam sensor that is used in the rear of the block. I believe I saw someone post a drawing of the internals of that sensor type compared to a standard proximity hall sensor. Its' orientation is critical as well as it being centered.
Next time I am playing with this stuff I will verify what I believe on the LS3 crank sensor. I believe if you feed it 5v or 12v it will only output 5v hence the need for a pullup resistor in that application where the signal needs to be higher than 5v. GM Mefi 4x controllers come to mind. Now, the cool LS3 cam sensor basically mimics whatever the input voltage is... 5v in, approx 5v out. 12v in, approx 12v out, as you saw.

Just noticed one other thing in your previous post, you said C2-39 and C2-73. I've never called them C1 or C2 and use Rx for Red connector and Bx for Blue connector. The cam signal input is on the blue connector B-73. The cam sensor ground is on the blue connector B-61. The cam sensor voltage is on the red connector, R-39.

It sounds as if you are not using both connectors correctly in the car. Hope this helps
-Carl

[Jim Blackwood]

Thanks for the correction Carl, that was a typo (or a brain fart take your pick) as pin 39 is on the red connector or C2 as you said. 73 and the ground are on C1 or the blue connector.

Bit of an oddity I noticed yesterday that might make sense to you. The new Delphi sensor PN 1P1209 from a 2005 6.0L Corvette tracked the input voltage as you said. However the one in the car returned a 5v signal. It is also the front mounted type but likely was sourced from either an '05 Silverado or Camaro, I'd have to dig far back in receipts to confirm. I'm uncertain if this will meet the voltage requirements of my ECM or not but as the sensor is very troublesome to access I expect I will just have to try it and see.

Good news on another front, I got a reply from Perytech and using multiples of their scope module is a simple matter of daisy chaining the external trigger to the square wave output with a jumper. Voila, I have a 4 trace scope. So today I plan to check all the coil trigger output signals.

Jim

[In-Tech]

Hi Jim,
The LS2 cam sensors(in timing cover) seem to be an oddity that I haven't spent much time looking at. I've seen Black LS2 cam and Tan LS2 cam, maybe that's the key. I have seen times where they required a pullup and times where they didn't. I think all of the LS2's used an E40 computer(24x 1x) and the LS3 is E38(58x 4x) and E67(58x 4x) and for sure those cam LS3 tan sensors are Voltage in = ~Voltage out. So, yeah the 2005,2006 stuff I have no definite truth. Maybe the SS trailblazer and Corvette has one and the GTO(australian) has another. Either way, sounds like you are making good progress.

I've never heard of that Perytech scope and just googled it. That thing is way cool for the money and is perfect for our BS car stuff. Really Really cool it can be daisy chained. I've got a 4 channel Rigol but I hate having to rip it out of my "lab" and drag it to the dyno. One of those Perytech's would be really cool in one of the laptop bags :thumbsup:
-Carl

[Jim Blackwood]

I'm just guessing the black/pink thing may be for something else, but the first two I bought were pink and the Delphi one was tan (Vette). I'm using the 0411 ECM so I guess once I get this thing to start I'll find out if the pink ones will work or not.

Jim

Sort of a good news/bad news thing today. The good news? Testing in-car, the pink CMP sensor outputs 10v on the sensor line to pin 73. So there seems to be functionally no difference between it and the Corvette sensor.

The bad news? the line goes high at TDC on the compression stroke. My fault, that's the way I installed it. But according to the scope graph on page 1 that's backwards and it needs to go low. Not usually a big deal but I have to remove the top radiator hose to get to the oil pump drive it is mounted on. Such fun.

[kur4o]

And here are some pics. You already figure it out, but other folks can benefit from it. Cant confirm the position of the small hole,[no piston available], but it looks like it is at the center of the sensor on #1TDC.

on 3rd pic the tab is pointing forward of engine. The line is parallel with the crank centerline. Just use the tabs on the sensor to get it right.

[Jim Blackwood]

What would be good with that is if you could use a mirror to show the sensor lined up with the hole and then a shot down the #1 cylinder showing the crank throw. I know it isn't as good as dialing it in but if the camera is on the bore centerline the crank throw should be centered. Either from the deck or the pan should work. If you feel like it.

Revisiting the relationship of the pulsetrain, CMP signal and #1 firing pulse, I realized that there is indeed a delay between zero on the pulsetrain and the #1 ignition event. That delay is most of the first rotation of the crankshaft. During the first full rotation the cmp signal is high and goes low on the second but the coil fires a bit before the second rotation begins. The first rotation makes up the intake and compression strokes. So based on zero the firing pulse is delayed until near the end of that rotation depending on advance. This can be viewed as consistent with industry practice provided one of two things. If the timing of all events begins at zero on the pulsetrain then the delay is nearly a full rotation rather than a sector such as 60 degrees, and due to the sequence of pulses the ignition events for selected coils can be triggered as soon as the crank begins to turn. I have not confirmed that this actually happens though. But I think it is important to recognize that zero on the pulsetrain coincides with the beginning of the #1 intake stroke and not with the firing of #1 cylinder.

Jim

[kur4o]

I will do my best to get more accurate measurements but it is really hard to turn that piece of iron in any other directions than straight on the ground.

Don`t forget that you have at least 14* spark advance + dwell time[charge time for the coil] that will be likely 10ms. Zeroing crank spark advance will get you #1tdc with firing the coil.
Speaking of dwell time, the on time for the coil before it fires. Can you take some scope measurements of the dwell time during cranking.

[Jim Blackwood]

I'm not sure how dwell time is dealt with in a COP setup. I was finally able to get scope traces of the trigger pulses along with the crank and cam signals and verify that my timing is spot on. The width of the trigger pulses at cranking speed is 7-1/2ms but with an independent power source and ground I'm not sure that has any effect on dwell time.

My ignition trigger pulses don't appear to be as consistent as they should though and this could be the reason for the no-start. To properly troubleshoot this I will need to complete the build on my benchtop simulator to include the cam sensor at a 1:2 ratio with the crank trigger and I would like to have a speed range from 200rpm up to as high as 8K but at least 2K. It's going to take me a few days to put that together but then I should be able to put the ECM through it's paces on the bench. I seem to be fighting this every inch of the way.

Jim

[In-Tech]

Jim,
I couldn't help myself, just ordered one of those Perytech U2200's :geek:
-Carl

[Jim Blackwood]

I think you will like it Carl, for a 2 trace scope it is pretty handy. It gets complicated when you start stacking them and then I think it's probably better to look for something else. But I did get a pair of them to work acceptably. I just prefer my test equipment to be more or less bulletproof.

I'm machining some parts today to build the simulator, I think I have all the pieces I need now. Had to wait on the timing set to come in. Should be able to get 2 or 3 speeds out of it. I'll post photos once I have something worth looking at.

Jim

[In-Tech]

Nice, keep us posted on progress. I have my Rigol DS1054Z 4 channel but as mentioned it's kinda a pain to have to unhook and cart it around besides the fact that it is super powerful and way smarter than me. :laugh:

I just built a crank/cam signal generator on an arduino thanks to a guy on the net that donated the freeware code(David J. Andruczyk, code is called Ardu-Stim). Here's a couple screen shots, encoded 24x 1x(LS1) and 58x(60-2) 4x(LS3). I am looking forward to having it run a pcm on the bench as soon as I get time to play.

[Jim Blackwood]

Very nice.
I want the actual parts for my simulator. I even went so far as to order the LS timing set (which sets me back to Thursday to start building, oh well.) because it has the flag cast into the cam gear. But the pulses coming out of the CKP sensor concern me a little, as what I am seeing is not a true square wave pulse. If you look at the trace I posted you should see that. I suspect it is due to the characteristics of the pickup (since it is a pulse generator also). Not sure if that has anything to do with my erratic spark outputs or not. I suspect a wiring issue will end up being the cause and if the simulator works correctly on the bench that will confirm it. That would be the simple solution.

Another possibility has to do with rotating speed. I want to see what it does at running speeds. We already know it acts a bit different when cranking.

Jim

[lionelhutz]

Did you post a waveform with a short enough time scale to tell how clean the signal was?

[Jim Blackwood]

Maybe not. The one on page 3 is the closest but still not great and I don't know what was going on with that wavy top line. I've attached one below. It includes the CMP trace and two coil outputs, #1 and probably #2.

On the CKP trace you can see steps in the verticals. This is more pronounced as the time base is stretched out and the pulse top and bottom get more noise. #1 coil trigger has an extra pulse and the 2nd regular pulse isn't quite where it is expected to be. #2 is flat, no pulses. #3 and 4 did have pulses but they were irregular, sometimes there, more often not.

Jim

[lionelhutz]

That 24x signal looks fine. The 1x signal looks fine too. I didn't double check the timing between them.

The steps are the scope sampling.

[Jim Blackwood]

That sorta makes sense I guess. I checked the timing and it is right. I misstated the coil spikes as what I had connected was the first 4 in the firing order, and at one point I was looking for 1 and 6.

Am I correct in thinking that with just the CKP input the ECM should put out coil pulses? Is there any other input that it absolutely has to have first?

Jim

[kur4o]

You can monitor the coil firing at the PCM coil control pins.

pins connector c2 [RED]
26 cyl1
67 cyl2
69 cyl3
29 cyl4
68 cyl5
28 cyl6
27 cyl7
66 cyl8

It is 0-5v signal. When the signal goes high the coil starts charging. When it goes low the coil fires. The high time [charge time] is the dwell time of the coil. At startup it should be around 10ms. When the engine runs it will drop to 3-4ms.

I will be really glad if you can measure it.

Each coil fires once per 2 crank revolutions, so you will get 1 coil pulse every 2 crank rotation for a given coil.

[Jim Blackwood]

I will be really glad if you can measure it.



I got 7.5ms while cranking.

Jim

[kur4o]

Thanks for sharing the measurements. I guess you have a constant power supply at fixed voltage. Do you remember what is the voltage reading during the test, and if you can vary it, a test in the 9-10v range will be awesome. I need that data for another project for retrofitting ls1 coils on older engines.

[Jim Blackwood]

That was on the car with the plug disconnected from the coil and cranking on a fully charged battery. I really won't have anything further until the simulator is built, and my power supply for that is a wet cell battery for emergency lights and a 15v laptop brick that I use to recharge it. I expect to upgrade to a trickle charger but have no plans for a variable supply voltage at this time.

Jim

[kur4o]

I thought you were running only the pcm wired on a bench. Cranking the engine will bring down the voltage to 10volts range, so no need for further testing.

I think you should change the injector and coil order to the engine specs you have. Stock ls1 uses different firing order than earlier SBC. It can be fixed in the software but you will need to get an obdlink device to flash the pcm.

[lionelhutz]

Yes, it should start firing plugs with the CKP when missing the CMP.

With a failed CMP, I suspect the PCM will begin firing the injectors and plugs assuming the CMP signal is low and the engine began cranking on the #1-8-7-2 firing rotation. Then, when the CMP is supposed to go high to begin the #6-5-4-3 firing rotation it flags that it failed but just keeps going in the order it began. So, if the engine began cranking on the #6-5-4-3 firing rotation then the engine and PCM are off a rotation and the engine won't start. So, you stop cranking and hopefully the engine stops on the #1-8-7-2 TDC rotation so the next time you start crank the engine the PCM and engine rotation match and it runs.

[Jim Blackwood]

Actually I'm not sure it can be changed in the software. You can change the bank assignments but I believe that only affects the feedback from the knock sensors and maybe the O2 sensors. But never fear, I have done the correct pin swaps to match the 18436572 firing order for both the coils and the injectors. There are two pairs that have to be switched but I don't have that info handy. Maybe the 4 center cylinders?

That cranking may have been (probably was) with the plugs out.

I'm using the OBDLinkLX and TunerPro, PCM Hammer

Jim

[Jim Blackwood]

Lionel, that's not quite what I'm seeing on the scope but I'll wait to see after the simulator is up. But it looks like maybe it runs through something like 4 cycles (8 rotations) before it switches. Again though, too early to say for sure.

Jim

[lionelhutz]

I think you should change the injector and coil order to the engine specs you have. Stock ls1 uses different firing order than earlier SBC. It can be fixed in the software but you will need to get an obdlink device to flash the pcm.

This can't be fixed in the software. I can't recall what it is offhand, but there was something to set that appears to allow you to change it in software except it doesn't work. You must re-wire the injectors and coils to match the firing order LS 1-8-7-2-6-5-4-3 to the Buick 1-8-4-3-6-5-7-2. In other words, swap 7-4 and 2-3.

Then, you set the bank select for firing order vs cylinder side so the O2 feedback on each side corrects the injector fueling on that side. The Buick firing order would use 01101001.

[lionelhutz]

Lionel, that's not quite what I'm seeing on the scope but I'll wait to see after the simulator is up. But it looks like maybe it runs through something like 4 cycles (8 rotations) before it switches. Again though, too early to say for sure.

Jim

Thanks for confirming that. So, the PCM tries a bit then switches if you keep cranking. If you don't crank long enough then it'll be luck of the draw on the next start.

And you beat me to the firing order and bank select post.

[DavidBraley]

I just wanted to say Thank You! to Jim who started this thread and all the others who have joined in. It's become super valuable information for me on my own quest to adapt the 24x crankshaft reluctor and 1x cam signal to my older V8 engine. :rockon:

[risenol]

Will follow along this thread, would like to contribute more but my own research is way more limited to what you guys got so far. Got covered the 1x on cam(on paper) but the 24x reluctor wheel seems to be more complicated as you guys have shown, great job in what you have accomplished.:thumbsup:

[Jim Blackwood]

OK, now I have something for show-n-tell.

The attached photo shows my now usable desktop simulator. Still a few things to do, I need to align the timing wheel to the cam sprocket and then do a little finer balancing, label the switches and test points, and as time passes I will add inputs and outputs to the test points, and probably some devices too. The one thing I really want at this point is a tach but I'm sure I can find something cheap online to fill the bill.

As it stands, using the variac I can get just about any speed I want out of it (the toggle switches on the right give me 2 speed ranges) and I have test points for CKP, CMP, Tach, Coils, and injector outputs. Plenty of room to add.

Should be able to give it a test run this afternoon I hope.

Jim

[kur4o]

I am not quite sure but it looks like the crank sensor needs to be rotated 180 degrees. The tab should points to the front of the engine.

[Jim Blackwood]

The rotation is in the opposite direction (CCW) so that messes with the way it looks. If you took the entire tone wheel and CKP sensor and rotated them 180 it'd be like the pickup being at the original mounted position but both the tone ring and the pickup facing rear instead of the front. As it is, the front face of the tone wheel is facing rearward and so is the sensor. With it running backwards that is like looking at it from the flywheel end sort of. Yep, messes with yer head but think about it. Maybe I haven't got it right yet but I think I do.

OK, so moving the whole shebang to the front of the engine and rotating the sensor around to the driver's side, no big deal, keep the sensor pointed to the front just like original. Running backwards, the relationship of the tone wheel and sensor stays the same so sensor pointed to the front side of the tone ring. Flip 'em both around. Rotate on the shaft as needed. Yep, I think that works.

For the CMP sensor I think it makes no difference except that the sprocket is spinning backwards, a leading edge is still a leading edge and I don't think the rotational position of the sensor matters. But tell me what you guys think.

Here's a couple more shots. I have a 30sec clip of it running but the balance needs a little more work. I'm headed back out with the laptop to hook up the scope, hope to get a trace or two this afternoon.

Jim

[kur4o]

If you flip the wheel and sensor 180 degrees, and switched the rotational direction of the crank you will be good.


That setup looks nice, Do you plan to make a full bench simulator. With the 4 channel scope you can make very good test station for discovering new stuff in the ls1 pcm. Like confirming EOIT target and dwell times and so on.

[Jim Blackwood]

Yeah, I'm having a little trouble with the scope. For some reason now when I plug in the USB cables to the scope modules my touchpad gets hinky and I can't control the cursor. Acts like an interrupt problem but there's nothing else connected to the laptop so I don't quite get it. Maybe I can get into the control panel and find some way to manually set IRQs or something. That worked back in the old days but with windows 10 who knows?

Anyway, with just one module plugged in (2 traces) I was able to look at the trigger pulses and cam pulse, then using the cam pulse as the trigger, checked each spark output. (The test point grid makes that really easy to do.) Looking at them in sequence for the 18436572 firing order they were all in the right places, the pulses were nice and square at 4ms duration, and I saw no evidence of erratica. I'm going to look at it tomorrow with a longer pulse train, then go to cranking speed and see what it does. I also plan to add a series of diodes so that I can look at the full 8 pulses on one trace, maybe split 4 and 4 also. It'll cut down the voltage a bit but I don't think that's a concern.

As for refinements on the simulator, yeah, over time I will be adding functions, like TPS and other sensors, IAC and other outputs. If I can find the old schematic for the panel maybe even add in the nixie tubes. But first I think I will take the tone wheel off and weld slugs into the holes to get a closer static balance. Adding weights in the back side of the mounting flange is only doing so much and I want it running a lot smoother than it does now. That can wait until I finish getting the car to run.

Which is what I'm back to now. The test I ran today demonstrates that the ECM in the car is OK and gives the correct outputs. So now the question is, why doesn't it do that in the car? I'm pretty confident that my leads to the coils are good. I used terminated wires pulled from a GM harness so they are factory crimped and the correct colors. They are well protected. But I will run continuity and grounding checks as a first step.

If that tests good, what else could be the cause? Back to trigger signals? Supply voltages, grounds? The answer has to be there somewhere. This is assuming of course that the cranking tests tomorrow on the simulator give the expected outputs. I guess that is step one.

Jim

[kur4o]

Open device manager and see if the usb device is not installed as a ball point mouse. I had some issues with serial com usb device install as a mouse.

Now that you have confirmed that there is a good spark signal, next step will be to check injector pulse, if it there is any and it is consistent overtime.

If all is good a step by step in car troubleshooting should be done. First will be to test for spark, than for fuel and work from there.

[Jim Blackwood]

Thanks, I'll try that next trip out. For now it's working OK on just one O'scope module and that's working out for me.

So the diode trick worked just fine even though I used 15v zeners, just because it was the only thing I had more than a dozen of. I guess LEDs would work just fine too, I have a bunch of those. They are just less robust. I paired up 1,8,4,3 and 6,5,7,2 and then put another diode from each of those two test points to a third, making it the full ignition pulse train. Kinda like those old Sun engine oscilloscopes in grampa's garage. Makes it real easy to look at the pulse train. Then I cranked up the speed while on the "8" test point until the pulses overlapped. I'm guessing that may have been around 4-5K rpm but I didn't measure the time interval and with no tach, well... Then I slowed it down to a crawl, adjusted the time base and switched the motor on and off a few times. The pulse train is real stable and it looks like it begins firing within a turn or so but I'll try spinning it by hand just to see when it starts. I just didn't think of it. The pulses never varied in width as far as I could see, or at least not by much. Looking at the "8" TP (TP-8 I think will be it's designation from now on) it's easy to see why COP is an advantage.

So I'm thinking I need to use the simulator to generate the CKP and CMP signals for the system in the car and see what sort of pulse train I get. That could get a little tricky as they are on separate batteries and both ECMs will be connected since I only plan to carry the signal leads and a ground over, but I don't think there will be enough of a voltage difference to matter. I probably should make up a combiner cable for the coil pulses though as it'd be handy to have the full pulse train. So yep, I'm gonna work on that for a bit. This way I won't need to be concerned about all that cranking on the starter.

Anyway, I should have known this but you can't really run the battery charger while testing. Luckily I have both a power switch for that and one for the battery so I can just switch it off rather than having to unplug. Running on the battery the traces are nice and clean.

Jim

[Jim Blackwood]

Some good test results today.

First I made up an octopus rig with diodes to combine all of the coil signals from the engine end of the harness. Then I unplugged the ECM from the simulator, left the power switched off, unplugged the cmp and ckp sensors on the car, jumpered the simulator sensors over to the car's ECM and tested with the key switch on and running the motor on the simulator. The result was a good solid trace for the CKP sensor, the CMP sensor, and then most importantly, the ignition pulsetrain.

Skipping ahead it seems most likely that the ckp sensor is bad (new). However it could also be the coil pack harnesses or the CKP sensor harness. So tomorrow's test is to swap out the ckp sensor, and then pick up the coil signals at the individual coils. Those two tests should be the final ones.

Jim

[Jim Blackwood]

To update and more or less close out this thread, I swapped in a new CKP sensor and now everything is working reliably. I don't think the sensor was bad, I think it was too far away from the tone wheel. Based on my experience I think the gap should be no more than 1/32"

So on with tuning and this is going to take some work. I do have one quick question, Other than the Moates '411 ECM with the external port installed (Around $600 I think) is there a less expensive option for real time tuning? I'm an old hand at that cheapie DIY built it yourself aftermarket controller and am doing OK learning TunerPro but I really miss being able to tune in real time. Is there any other alternative besides the high dollar guys?

Jim

[lionelhutz]

Moates is the only real-time option because it directly replaces the memory chip with an emulator. HP tuners and EFI Live don't do real time. No ODBII port tools do.

[NomakeWan]

You can do pseudo-realtime with the stock $EE 8051 PCM. Changes can be made on the fly to fueling, timing, etc, which can then be transferred into TunerPro to create a BIN which can then be flashed relatively quickly to the PCM. Of course this PCM doesn't handle direct control of coil-on-plug setups like the 0411 conversion from TORQHEAD and others would, but gonna put it out there anyway.

[In-Tech]

HpTuners used to do a real-time ram based tune as well. You make your changes real-time then save the file and burn it. I only used it once to try it out, can't remember if it cost more credits. I have a roadrunner when needed so it was just a test for me to check it out.

[brian617]

Doesn't HP Tuners support Real Time Tuning with their Custom Operating Systems? Or am I just dreaming that up?

[Jim Blackwood]

I'd have thought this would be ubiquitous. MS does it with a serial port which is of course old tech and has for about 2 decades. It makes initial setup and tuning pretty easy.

Jim

[lionelhutz]

brian617 - You're right, HPT can do RTT on some of the older gen3 PCM's. Probably a 0411 would be supported. But, it's limited in what can be done since the tables being used for RTT have to fit into the PCM RAM.

Jim Blackwood - The data running the engine isn't being transferred over the serial interface. All that is being done is writing changes to the tables in the MS via it's internal software and hardware setup. Same with ODBII, the PCM has to have the modifyable tables in memory and a way for the laptop program to modify them via the ODBII port. It's difficult in a GM PCM because it's not built to allow the ROM tables to be modified while the engine is running. So, you have to put a couple of tables into RAM and use them from RAM.

Planning for it and building it into the design is much easier then trying to get an existing PCM not meant for RTT to be able to support RTT.

[Jim Blackwood]

Thought I'd bring this thread up to date. After experimenting with PCMHammer (great app by the way, thanks guys, you are the best!), PCMLogger, EFILive, and HPTuner, as well as a few Android apps, OBDLink, and AllPro, and finding that they all have their strengths and weaknesses, I settled on HPT as having the features and resources I needed for this build. It wasn't an easy decision. Key elements were the availability of a 2 bar mod for the 12212156 OS and real time tuning, although now I realize that the RTT appears to be nerfed compared to what Megasquirt has which is just sad. OTOH, with their other tools it's not at all essential. Anyway, HPT won't do anything that the others can't do, they just have a well developed user interface. And you pay for it. I don't mind them turning a profit, I just think they are a bit aggressive about it. Still, for me it's a one time expense and again, pro/con, the licensing scheme is not user friendly.

So, having been helped to a good OS by friends here (thanks Carl), a 2 bar mod from HPT, and maps from a tune on their download site, plus considerable use of the benchtop simulator I built, gradually overcoming all the hurdles and most of the flaws in the systems, (both benchtop and in-car) yesterday I was able to start and run the car on the new OS. It was pig rich and half my scanner didn't work but the AFR graph was showing a 7.4:1 ratio. After some thought, I cut the entire VE table in half. A little more thought and I would have realized that was the wrong calculation but after fattening it back up by 1.2 twice I was in the 12-13 range and the engine was sounding perhaps as good as it ever has. I've leaned it by 98% for the next run and will do a full warmup and look at the AFR then, it should be close. At that point I'll have a look at the RTT and see what I can do with that. Then it's on to startup and warmup enrichments but as it stands it starts fairly easily on the second crank. Lights off, almost dies, then settles into a smooth, if rather high idle. All of which is fixable. Once I'm reasonably close I'll clone the ECM and sort out the issues I still have between the simulator and VCM Scanner, while keeping the original in the car until I'm finished tuning. At that point I plan to swap the clone into the car and keep the original on the simulator. I have a 3rd backup '411 which I will also eventually clone and carry in the trunk as an emergency spare when on trips.

So at this point I am going to declare the program as a success. A future upgrade includes a new engine based on the Buick 300 with a 340 crank (5.6=5.7L) and blower, using TAPerformance Rover heads (parts are at the machine shop). And when I feel like pursuing it, I have a 20K mile 8 speed automatic (AA80E) on the shelf ready to bolt up (It has been installed in the car before and run in limp mode). That will require the ECM and TCM out of the Caddy CTS-V, so not the simplest upgrade, but should be partially completed already. I just need to buy the controllers. But before that, I need to drive the car for awhile. Most likely getting the cruise to work again and then completing the AC install will be the priorities.

A warm thank-you for all the help folks here have given me. This has become one of my favorite forums, mainly because of the helpful attitudes of a number of standout denizens. I can point out a couple of other excellent forums if anyone has an interest. For LBC (Little British Car) enthusiasts, BritishV8.org and MGExperience.com, and for bus/RV conversions busconversionmagazine.com/forum is good. Maybe I'll see some of you there as well.

Jim