Alrighty, so I just moved way up north to Washington from Texas. My lady and I moved up here to be closer to her family and better opportunities, well theres been an agreement on me and my lady's grandfather, Del, he has 1989 F150, 4x4, Single Cab, Swb, with a hopped up 351.

So Del has been telling me the problems on this truck and it kinda has me lost diagnostically but I do want to ask questions about this darn thing. Del decided to take the old 351 block out did some work to it and put it back in. Well shortly after he started to experiencing weird problems with it. When you turn the key into the on position, the fuel pump runs constantly and will cause the truck to not want to start. He replaced the the fuel pump and something else I that I cant remember.

It'll run strong for a little while and start having problems, Del unplugged the battery for 10 days, hooked it back up and it started right up. Once again, it would run strong for a good bit and then just die. Well I got to put my hands on it and all I did was unplug the fuel pump relay, turned the key on, and the fuel pump never made a sound. I connected the relay back in, turned the key, and the fuel pump run constantly and not start.

My guess is that I need to probably backtrack that wiring and check for a bad ground? Any help is appreciated!

If I left anything out, i'll try to update this.

 

Fuel pump running all the time, it's a good chance the computer is bad or going bad. Pull it and check for any damage.

 

computer has been pulled and replaced in the past

 

Given the age of these computers you very well may have another bad one. Pull it out and inspect for signs of a leaking capacitor. Your symptoms are pointing to a bad PCM again.

 

I concur with checking the computer

 

Remembering what the owner had told me, I could have sworn he replaced the pcm more than once. But I very much will look more into the computers n stuff

 

When you are getting the constant fuel pump running/no start condition try running the Key On Engine Off (KOEO) tests and Stored Code display. Another confidence test to see if the computer is functioning.