After PCM Reset, now no longer starts.

NANCY ARIAS

MEMBER
1993 FORD F-150
5.0L
V8
2WD
179,000 MILES

Hello, my son has had some troubles with his truck, changed oil, fuel pump, fuel filter, spark plugs, and AIC, would run until it got warm then would die. Would restart after cooling back down. After changing the items listed above, same problems persisted, so he reset the PCM and now it does not start at all. It turns over but that is it. Hope someone can help. Thank you!

1 Reply

CARADIODOC

MECHANIC
33,873 POSTS

There is no such thing as "resetting" a computer. GM had a real lot of Engine Computer trouble in the 1980's and early 1990's. Often disconnecting the battery for a few minutes caused them to unlock and temporarily work again. That "fix" has carried over to today when many people think that works to solve all kinds of problems on any brand of car or truck.

Other than the fuel pump, the parts you listed wont cause stalling. The place to start is always by reading and recording the diagnostic fault codes, but if the battery was recently disconnected or run dead, those will have been erased and that information will be lost. The next thing is to determine if youare missing spark, fuel pressure, or both. If you have spark, listen if the fuel pump runs for one second when the ignition switch is turned on. If it runs for that one second, but there is no spark, we need to look at the ignition system.

Based on your dandy description of the symptoms, the best suspects are the pickup assembly inside the distributor, and the ignition module bolted to the side of the distributor. Unfortunately there is no quick way to test either of them. We never approve of throwing random parts at a problem and hope one of them solves it, but this is one time when the parts are relatively inexpensive, and those that do not solve the problem can simply be saved for another day. The pickup assembly and the module each often fail by becoming heat-sensitive, then they work again once they cool down for about an hour. It is common for them to keep on working as long as you are driving and there is natural air flow over the engine to keep the parts cool. Most commonly, the symptom is a failure to restart shortly after a hot engine is stopped, as in when stopping for gas. That is when "hot soak" occurs. That means the heat from the engine migrates up to the distributor instead of being blown away. Intermittent failures like this are only temporary. It is usually not too long before it becomes a permanent failure.