I have some weird issue with a '78 Trans Am project. The engine is modified 350 with aftermarket TPI setup. I am using 16197427 PCU with MPFI mods (jumped resistors and memcal mod), $31 mask PROM (can't remember code at the moment, will post it tomorrow) modified mostly based on TBI to MPFI document.

The problem:

Engine starts fine first time, runs pretty OK in open loop, runs fine although a little bit rich (just needs more tuning), when hot and in closed loop, but after switching the ignition off, it even won't show any sign of starting.

Checked spark, checked fuel, everything seems to be OK, after some time of cranking, the spark plugs are slightly wet. After standing few hours, car starts and runs fine again, until stopping the engine. Then it won't start again. There is no difference between cold or hot engine, starting problem is common - starts at first time but not after. When engine is cold, spark plugs are more wet after shorter time of cranking, but I think it is normal.

Could anybody direct me what could be the reason? Could it be PROM related or some kind of physical problem? Where to start troubleshooting?

 

This may sound stupid, but might check coil wire continuity. I had same issue on other than cold starts. Coil wire had bad connection at one end that apparently was affected by higher temps. Replaced and problem solved.

 

Sounds like part of the ignition system is heat sensitive and isn't working with the reduced cranking voltage when hot.

GD