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While I am very familiar with Ford/GM Ignition systems both electronic and points.... I am not that familiar with this one. This being a 66, I assumed it would be a mechanical / points type ignition system but appears to be electronic or at least converted to an electronic ignition system.
The problem I am having is that intermittently I lose the negative pulse to the negative side of the coil. I have +12 give or take after the ballast resistor at the coil but seem to lose the negative pulse. The vehicle starts and runs fine but after it is warm, I'll get a crank and no start with no output from the coil, after it cools down, starts right up again. Will start over and over until it runs and gets warm then the same thing.
Does anyone have a schematic for this style ignition that I can look at? Can anyone identify this type of ignition system?
That's a Chrysler electronic ignition the vehicles been upgraded to.
Basically the big 3's early electronic ignition systems fundamentally worked the same. There is a 2-wire magnetic pickup (aka variable reluctance sensor) inside the distributor that produces a small AC voltage. That voltage is fed to an ignition module box (aka ICM) in this case that orange box, if it was a ford then a duraspark box, if it was a GM a 4 pin module mounted inside the distributor. The ICM then triggers the coil to fire by opening it's transistor connect to coil negative, breaking ground
Of coarse there are some small differences. Chrysler kept the ballast resistor... I believe Ford used a resistor wire?? and GM went all in on full battery voltage.
If your losing your trigger pulse at the coil negative terminal I would check:
There is an AC signal coming out of the distributor pickup wires while cranking ( believe the range should be 0.2 to 1.5 VAC)
ohm out the pickup coil (i'm not sure what the reading should be as it will vary with temperature but it should not be shorted or open. Also make sure the coil is not shorted to the distributor housing.
make sure the pickup air gap is set correctly.
I would check this stuff before and after the no-start condition.
If the pickup checks out I would suspect the ICM. If you replace it make sure the screws that hold it to the vehicle are not loose. The box gets ground through the mounting hardware.
oh, make sure the charging system isn't overcharge. I've had that cause ICMs to overheat and shutdown.
That's a Chrysler electronic ignition the vehicles been upgraded to.
Basically the big 3's early electronic ignition systems fundamentally worked the same. There is a 2-wire magnetic pickup (aka variable reluctance sensor) inside the distributor that produces a small AC voltage. That voltage is fed to an ignition module box (aka ICM) in this case that orange box, if it was a ford then a duraspark box, if it was a GM a 4 pin module mounted inside the distributor. The ICM then triggers the coil to fire by opening it's transistor connect to coil negative, breaking ground
Of coarse there are some small differences. Chrysler kept the ballast resistor... I believe Ford used a resistor wire?? and GM went all in on full battery voltage.
If your losing your trigger pulse at the coil negative terminal I would check:
There is an AC signal coming out of the distributor pickup wires while cranking ( believe the range should be 0.2 to 1.5 VAC)
ohm out the pickup coil (i'm not sure what the reading should be as it will vary with temperature but it should not be shorted or open. Also make sure the coil is not shorted to the distributor housing.
make sure the pickup air gap is set correctly.
I would check this stuff before and after the no-start condition.
If the pickup checks out I would suspect the ICM. If you replace it make sure the screws that hold it to the vehicle are not loose. The box gets ground through the mounting hardware.
oh, make sure the charging system isn't overcharge. I've had that cause ICMs to overheat and shutdown.
Thank you very much! This is helpful. So the ICM overheating shutting down sounds like the issue I am having. It runs perfectly fine until warm then go to start it and no - to the coil. When GM Modules go, they go and that's it. It is rare to see an electronic device due when warm, it usually works or it doesn't!
Thank you again, I'll get back on it, much appreciated!
