No start manifold backfire

[DarkestCon]

1989 bonneville sse
No codes, no starting, nothing. just cranks. Mechanic said they ran all the tests they could and cant find anything. thats 2 different shops. Mechanic says he could get it to run for a few minutes then it would just die. Motor has less than 4000 miles on it. ecm is a replacement less than a month old. new manifold gaskets. Has fuel. has spark. No idea what the problem is. Vehicle has less than 98000 origional miles. well cared for i have all maintenance receipts etc.

Debating to sell it for 900 as interior is all leather etc. all in 9/10 condition as is body. or trying to take it to a dealership to see if they could figure it out. Any insight would be welcome.

[96 SSEi]

hi, welcome to the club!!

please use this to diagnose your issue and post your results pl......http://troubleshootmyvehicle.com/gm/3.8 ... ondition-1

[redfury]

new ECM, did you have to do a crank relearn with a scan tool with the new engine? The computer needs to determine the crank count with the CPS in order to set the timing for fuel and spark. I'm not as familiar with the OBD1 computers, but they are still fuel injected and need certain parameters in order to run right. I would call the dealer and ask them if the ECM has to be calibrated before it is put in your car in order for it to run. It might be something that simple, but something you don't have the capability to do.

[RJolly87]

I don't believe OBD 1 has that functionality. If anything, that's all stored on the EPROM chip that would have been switched over.

If the crank position sensor is bad, or the ICM is bad and not passing the crank signal to the computer (or even wiring issue) it could cause the issues being described. If the computer doesn't know it's cranking, it won't know to do anything.

Are the injectors injecting? Have you verified fuel pressure is what it should be?

[Jrs3800]

There is no crank learn or the like on these older ECM's... The ECM simply learns over time.. all of the basic info such as the tune are stored on the MEM-CAL Chip..

I agree with Randall, look at the crank sensor, ICM( Ignition Control Module )... Fuel pulse at the injectors and fuel pressure.. And as a last resort The ECM( I hate Aftermarket ECM's )

[DarkestCon]

Sorry i hadnt responded. Ill definitely check out that link. Heres a bit more detail about what i know. I bought the car thinking i would be able to fix it. for 500 dollars. Ive checked fuel and spark. Both are present. The car came with all paperwork from the day it was bought as its a 1 owner car and the guy kept good paperwork. 3 years ago the engine was replaced. I dont know why, it still has less than 3000 miles on it. Engine bay is spotless. As of 4 months ago he took it into the shop and the shop replaced manifold gaskets, spark plugs, wires, and the ECM. 2 days later he drove the car off the lot.
that same day the car went back in the shop for not running, they replaced the ECM again from manufacture warranty. He then took the car home.

I am unsure how long or exactly what issue showed itself. just that he parked the car in his garage and that was the end.
The dealership he was taking the car to went out of business at the time i purchased the car. I had the car taken to a mechanic who looked it over for about 4 hrs and couldnt figure out the issue. he confirmed fuel pressure. I had been unable to start the car as it would just crank and backfold at the manifold. When i did get it to start 1 time it was barely running and sounded and felt like it was about to die as it did. He says he got it to run off and on for 5 min. But he couldnt figure out the problem so he had another mechanic take it to his shop as they had the proper diag tools. The 2nd mechanic says he ran all diagnostics and nothing. No codes, everything looked fine. and now I have to get it towed home lol.

[NoShowCar]

I just went through a similar problem. Car was running fine. Was in long line of traffic for 45 minutes. Car was not overheating, but I'm sure it was very hot under the hood. Shortly after leaving the line of traffic, on a side street, it started sputtering and just died. I figured hot fuel. 1 hour of cooling did no good. Cranking resulted in backfires and what sounded like cross firing plug wires. Overnight cool-down did no good. Towed home and verified fuel delivery. Must be spark timing. Pulled C3I Module and coil pack. Resistance and continuity on coil pack checked good. No way to check C3I Module so bought a new one. That worked.
Here's the kicker. On close inspection of the C3I Module wires, it looks like one of the primary wires was trapped and pressed onto one of the uninsulated terminals where they can overlap the wires. This is in the space between the coil pack and the C3I Module when they are bolted together. I think what must have happened was the terminal pressing on a wire finally pressed through the insulation and that resulted in cross firing (firing out of correct sequence) of a coil. The C3I Module is probably OK, but I started digging into it to see what was inside before I noticed the condition of the wires and ruined it (I thought it was shot anyway).
This may explain such behavior when a car just won't start, but tries to and won't keep running. OBD won't show this kind of problem.
Car is running fine now.

[NoShowCar]

Update on NoShowCar problem fix. Now 3 years later and engine still runs fine. Correcting primary circuit short between C31 module and coil pack (in the cavity between them) was the answer. That required a close eyeball examination of all the parts. See description in post above. No computer diagnosis would reveal that. Too much reliance nowadays on "computer analysis". The basics always apply.

[95naSTA]

Thanks for circling back. Hopefully it'll help someone in the future.

[NoShowCar]

Has been running fine for nearly 4 years now, but - - and this may apply to issues newly posted above. Car has been running fine except in cold weather it had episodes of no fire while cranking smartly. Acted like no fuel. When it warmed up a bit, it would light right off just as normal. I suspected water condensation freezing in the fuel line. This happened several times. Wintertime fuel additive (methanol) seemed to fix it for a while. Now very recently, going down the road, the engine died completely. After parking on the shoulder, cranking gave no start just as when freezing was suspected. Now, when the key was turned all the way off and reinserted, it started right up. I suspect now that it is an ignition switch problem. The issue recently posted above may be this problem. Getting to this switch looks like a headache. I'll update as this is addressed.