Hi I have a pretty frustrating problem and have looked through posts for a similar problem.

I was driving down the road and my Z28 started running rough and then died. I could not get it to fire and towed it home.

I read some posts and said: aha... must be the ICM or coil. So I replaced them and the car would fire a bit but not run.

So I said must be fuel and I replaced the fuel pump and filter. My psi showed I was getting 40 psi of fuel but as soon as the key is turned of it would drop to zero. Thinking this was a problem, I checked for an open injector. They all Ohmed out ok and I used a stethoscope to listen to them and they are all clicking away. The FPR has no fuel in it and it does hold 35-45 lbs of pressure in the system when it is running.

At this point I got the engine to fire up for the last time, I had been playing with the timing and had the brown./black wire disconnected to do the base timing. The motor was running pretty decent with an odd miss while idling.

I revved it up bit and the motor quit and I haven't been able to get it started since...fak

So the only thing left was the pickup coil in the distributor... I changed that and swapped another working ICM in at the same time. Put it back together and no go.... I sprayed Quick Start into the Throttle Body but it didn't fire at all...

This morning I will put cylinder 1 to TDC and double check that the distributor is pointing in the right direction... if no go I will take the distributor out and check for spark again. I know the injectors wont fire without the ECM, but the ICM pulse for spark drives the ECM right?

My question: What's the chance that my ECM has gone bad? Does anyone know how to test it? Someone has played with the wiring under the dash and I can't find the diagnostic port to check for codes. There is no check engine light on.

Thanks for reading my essay and any suggestions greatly appreciated

 

The problem turned out to be a shorting rotor. The guy I bought the car from had replaced the distributor with a cheap aftermarket one (red plastic).

I took the distributor out and hooked it up so that I could turn it by hand and see if there was spark. I was getting spark from the center post but not from the outside posts. So I took it apart and sure enough the rotor had a black spot on it under the contact.

I replaced it with an original gm rotor and cap I had sitting around and the car has been running great since then!

 

happy car