My 1990 F250 5.0 will not start. I think I have the problem pin pointed to the PCM but would like some thoughts. Engine gets spark. When I turn on the ignition but do not crank the engine the fuel pumps keeps running and does not shut off after a couple of seconds. It does the same when I switch to the other tank.

I replaced the fuel pump relay with no change. I have checked the EEC power relay and it is getting and sending the correct voltage. The biggest clue I think is that I cannot get any codes. First I tried to read codes with my code reader but the test would not initiate and no codes read. I then tried to do it the old fashioned way to read the CEL light but the test will not initiate. Bad PCM?

 

Check your pcm ground but yes sounds like a burnt board.

 

Sounds like you may have a bad PCM. Can't retrieve codes, fuel pump(s) don't shut off/continuous run with key in ON position. I know the feeling. Just went through same problem.

 

Remove your PCM and open it up.
Here's most likely what you'll find.
Click this link: A9x ECM's (and same years ECM's) Failures Due to Age

Let us know what you find.

Bob

 

Well that was it. Pulled the PCM this morning and opened it up. When looking down onto the board, the very first blue, electrolytic cap on the right burst on the bottom. It fried the board around it and the long trace running from the main terminal connection is gone. About a 1/4 inch of it is gone. I don't think this is repairable so I am going to go look for a new PCM.