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.

 

I am guessing that you are pulsing the purple / white wire (dist ref pulse in) at the distributor connector. I'm not sure if that is a valid test - did the shop manual recommend that? I would look at the injector signal from the ECM with a scope, while cranking the engine, to determine if they are being switched or not. What is the fuel pressure during cranking?

Tim

 

Yes, it's the purple/wht wire and yes the factory service manual has that check in their troubleshooting tree.
The fuel pressure during cranking is 45 psi.

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.

 

Interesting test......That ECM must be drawing quite a bit of current with the ign off to heat itself up that much. What's the current drain from the battery with the ign off? Sounds like there's an internal short in the ECM. Does the current drain go away when the PROM is removed?

Tim

 

Do you have an aftermarket chip in it? I don't know about your problem, but I had an aftermerket chip in my car. I burnt up 3 computers before I decided to stop putting the aftermarket chip in. After that I didn't burn up any more computers.

 

I do have a custom chip in it. I am also on my 3rd computer. The first lasted 6 months.
The second and third get hot with ignition off and will not start, when they completely cool down everything is fine so they are not toast yet. I don't know the current draw yet, still need to check though.
I've never heard of a PROM taking out ECM's.

 

I dunno about the proms our cars use, but a lot of proms we use in computers can blow daughter boards real easily. If its a cheap
prom and the pins arc, it could cause a serious problem.

-- Joe

 

Wow, talk about digging one up from the grave. This was last year post.

Anyway the problem turned out to be a bad ignition module.

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86 Camaro Sport
383 Speed-O-Motive Crate Engine, Raptor 700R4 Tranmission, Trick Flow Twisted Wedge G2's, 58mm Accel TB, 3.73 Auburn Pro, SLP Cold Air Induction and Headers, Hooker Cat-back, Serpentine Belt Setup, Dual IROC Fans, Jamex springs, 16" IROC Rims, 36mm/24mm Sway Bars, Global West Steering Brace. Hotchkis Rear LCA's,Panhard Bar and SFC's.
My Camaro Project

 

Hahahaha.. no kidding. I didn't notice the date before I responded.

Glad you fixed it anyway.