Well it happened AGAIN. My car will not start. The injectors are not firing. I used a noid light to check them. They all do have power to them, no ground. The ground comes from the ECU pulsed batch fire. The ECU is told to fire the injectors by the distributor and that part works. I can also simulate the distributor by disconnecting the 4-wire connector and pulsing 12 volts that feeds the ECU. When the ECU sees this pulsed 12 volts it is supposed to send a ground to the injectors, it is not.
I have a 1227165 ECU (MAF system). The first one lasted 6 months, the second lasted one day and this one lasted 2 weeks. They were all Discount auto parts re-manufactured units. Lifetime warranty but who cares about that right now.
I have checked all the pins at the ECM for shorts to ground, power and chassis grounds with the key on using the factory service manual chart (pin by pin specs about what should be on each pin with key on).
Every pin checked good. Nothing strange.
On a side note my alternator is a little flaky now and again. Driving normally, the voltmeter is around 14 volts with everything on but occasionally it drops to 8 than back to 14 in an instant. Not all the time and not every trip, maybe twice a week. I am on my second alternator because the first one dropped to 8 volts once and stayed there, no output. Any connection to the ECM burning???????????
Thoughts?


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86 Camaro Sport
383 Speed-O-Motive Crate Engine, Trick Flow Heads, 58mm Accel TB, 3.73 Auburn Pro, SLP Cold Air Induction and Headers, Dynomax Cat-back, Serpentine belt setup.

 

It's possible the alternator is causing the ecm problem. When you say the voltage jumps up to 14 volts, perhaps it is going higher than what you see and is damaging the ECM. Have you checked the plug that goes into the alternator, I had a problem with mine a number of years ago, my voltage would jump up and down periodically and I had one hell of a time finding the problem. It turned out on of the connectors inside the plug was just a little too far away from the pins when plugged into the alternator. I bent the connector inside the plug to close the gap and I have not had any problems since. Something you might want to check. The other possibility is the re-built ECM's you are getting are junk, who is rebuilding them? A lot of times they are rebuilt to work but no other tests are conducted on them to see if there are any other problems.

Good Luck

Gary

 

Update-I pulled the ECM last night and took it home. It was very hot but I didn't think anything about it, it was in a closed car all day long. After work today I put it back in the Camaro to see if it would start but noticed it was not hot at all even sitting in a closed car all day(Jeep Cherokee). Well I put it in the Camaro and it STARTED! I didn't dare drive it home yet, besides I had two cars at work anyway so I drove the Jeep home.
So it seemes something is making this thing very hot and I don't know what.

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86 Camaro Sport
383 Speed-O-Motive Crate Engine, Trick Flow Heads, 58mm Accel TB, 3.73 Auburn Pro, SLP Cold Air Induction and Headers, Dynomax Cat-back, Serpentine belt setup.