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Thread: Retrofit 24x reluctor to early V8

  1. #16
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    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.

  2. #17
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    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.
    Last edited by lionelhutz; 02-24-2020 at 06:59 AM.

  3. #18
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    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

  4. #19
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    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.
    Last edited by lionelhutz; 02-24-2020 at 07:44 AM.

  5. #20
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    Post a picture if you can too.

  6. #21
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    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.
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    Last edited by Jim Blackwood; 02-24-2020 at 05:53 PM.

  7. #22
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    Quote Originally Posted by Jim Blackwood View Post
    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.
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  8. #23
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    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

  9. #24
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    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
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  10. #25
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    Quote Originally Posted by Jim Blackwood View Post
    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.
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  11. #26
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    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.
    Last edited by lionelhutz; 02-24-2020 at 09:38 PM.

  12. #27
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    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

  13. #28
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    Quote Originally Posted by kur4o View Post
    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.
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  14. #29
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  15. #30
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    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?
    Last edited by lionelhutz; 02-25-2020 at 04:40 AM.

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