I posted this in the I6 and the 86-96 forums, someody suggested I should try here. So here goes-

My problem with my 92 300 w/e4od has been ongoing and a PITA. Heres what the truck does. When I go to start it, and turn the key to on, the fuel pump starts, but instead of stopping, after pressure builds it keeps running. If I then take it to start, it normally wont start(I say normally because if it is very hot outside it will start) However, when it does start it idles really bad @5ooRPM's vs the normal 750-800. Plus, it runs VERY rich. The CEL is on, but I am unable to retrieve codes, as the computer doesnt complete the start sequence(When the fuel pump is stuck on).

I have checked the relays(Pulled them and checked them w/12V they, both the ecm and fuel pump, both pull in and out like they should). Also, checked spark(At the plug) seems ok. Checked fuel pressure(At fuel rail before and while running) both times it is around 50PSI. Also checked, the ECT(Resistance appears to do what it should and the reference voltage is 5V) Also checked MAP sensor(Ref voltage is 5V, I replaced it with a junkyard sensor, to see if they both do the same, which they did) so if it is bad then they both are bad. I know that there is a timer in the ECM that is supposed to open up a ground, and kill power to the fuel pump during start up. So,I went to fordfuelinjection.com and got a little procedure to check the ecm. I found I had a bad ground, which I repaired. But it did nothing. So, I am thinking I have a bad ecm, which the bad ground killed over time. Any thoughts?

 

If the 92 still had the ground at the Neg. Post of the Battery it may be off or bad other than that I would say a bad PCM.

 

Thanx Sub,

I pulled the ECM, opened it up, and there appears to be a burnt spot on the board, approx 3/4 in diameter, right by what looks like the main chip. Thats enough for me to shell out the $$ for a new one. Prolly be next week before I can get one to come in with the holiday and all. Thanx again! I just hope that the ground I repaired was the underlying issue.