No movement on the tach when cranking (Page 1/2)
Additivewalnut FEB 13, 12:19 PM
Alright, pay check came in, I'm ready to buy more parts for my problem child. I've narrowed it down to the pickup coil since I replaced the ICM and nothing happened. So. Do I need to replace anything along WITH the pickup coil as to not make it burn out the moment I turn the key? Or is it just pickup coil and done?

Oh there's an o ring I have to install too isn't there?
fierofool FEB 13, 05:03 PM
Pickup Coil, Ignition Module and Ignition Coil supply the spark. If the other components are good, as you indicate, replace the distributor O-ring when you reinstall the distributor. I don't know if it's available as listed for the Fiero, but it may be for the 93-95 Camaro and Firebird 3.4 oil pump drive. It's FelPro Part # 70800.
Additivewalnut FEB 13, 05:36 PM

quote
Originally posted by fierofool:

Pickup Coil, Ignition Module and Ignition Coil supply the spark.



Oh wait hold up then, would a bad ignition coil cause the tach to not move when cranking? From my research, only the ICM and the pickup would cause it not to..
Dennis LaGrua FEB 13, 06:50 PM

quote
Originally posted by Additivewalnut:


Oh wait hold up then, would a bad ignition coil cause the tach to not move when cranking? From my research, only the ICM and the pickup would cause it not to..



The tach pulses are taken from the igniton module to the coil. Iif the coil was defective and all else is good then the tach will show movement. The only other thing that could cause a tach not to get a signal is a bad tach filter.

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Additivewalnut FEB 13, 06:56 PM

quote
Originally posted by Dennis LaGrua:


The tach pulses are taken from the igniton module to the coil. Iif the coil was defective and all else is good then the tach will show movement. The only other thing that could cause a tach not to get a signal is a bad tach filter.




The tach was moving fine when the car died, now it doesn't move when cranking..
Gall757 FEB 13, 08:50 PM

quote
Originally posted by Additivewalnut:


The tach was moving fine when the car died, now it doesn't move when cranking..



By an wide margin, the most likely problem is the ICM. They die in all sorts of ways, sometimes right out of the box.

[This message has been edited by Gall757 (edited 02-13-2020).]

Additivewalnut FEB 13, 09:43 PM

quote
Originally posted by Gall757:


By an wide margin, the most likely problem is the ICM. They die in all sorts of ways, sometimes right out of the box.




Hmmm.. how do I test if mine's bad? I dont really want to just keep buying them if that's not the problem
DavidM FEB 13, 11:39 PM
First, make sure the distributor is actually turning. You can test the pickup coil's resistance with a meter - should not be open. Make sure that the power & ground is making it to the ICM (and check the pickup connection to the ICM.

Check the connections to the coil. I have not tried a test light on the signal to the coil (I used oscilloscopes) but I don''t see why that would not work if the ground lead of the test light is on the +ve. Possible that the tach filter is shorting out the signal but unlikely.

Could be just another bad new ICM of course. They used to be able to test them at the parts stores - don't know if they still can.

Keep at it! You'll solve it. Measuring is cheaper than the parts cannon!
Additivewalnut FEB 14, 03:11 AM

quote
Originally posted by DavidM:

Could be just another bad new ICM of course. They used to be able to test them at the parts stores - don't know if they still can.



I actually got my old ICM tested and they said it passed all the tests they put it through... I still bought a new one though just in case. I also bought a new ignition coil and have only run the car for a total of 1.5 hours. Everything seems to be pointing at the pickup coil going bad after sitting for so long. But I'll check everything, I need to go buy thinner multimeter leads to actually fit in the connector LOL
fierofool FEB 14, 08:35 AM
In the old harnesses, the clipss on the ends of the wires can get pushed back into the harness ends. It may not have caused the initial problem but look into the end of the plug and see if all the clips are at the front, equally. The pins on the ICM or other sensors can sometimes push the clips back inside, allowing the sensor to work for a while before it loses contact.

Have you checked a plug wire to see if you have fire on it? And since you have removed the distributor to replace the pickup coil, did you check the distributor cap to be sure the carbon button didn't fall out, or did you make my mistake and fail to reinstall the rotor button ?