Retrofit 24x reluctor to early V8

[Jim Blackwood]

CMP sensor and oil pump drive for Buick.

Jim

[dave w]

CMP sensor and oil pump drive for Buick.

Jim

Cool design

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.