91 f-150, 5.0, auto, 4x4
Heres the deal, when I turn the key to on, the fuel pump should make a running sound for a second then stop, (it's priming), then when you turn the key the rest of the way to start it should start,,, right? Ok I turn the key on, and the fuel pump will not prime it just keeps running, on both front or back tank. I thought some POS stole the gas out of the tanks so I put more fuel in, same thing, will not start. I'm trying to sell this truck, I bought a newer one, but I need to get it running first. DO I need a new fuel pump, relay, what might be up here.

 

What is your fuel pressure when you turn on the key? Does it hold pressure? For those who doubt both pumps can go out together my 95 F150 5.0 lost them both at around the same time.

 

there seems to be a pressure port on the fuel rail is that were I would take the pressure reading? After I go buy one that is.

 

Sounds like you have a bad PCM Computer.

 

got my hands on a pressure gauge. I have 44 psi with key on, does not bleed off when I turn the key to off. SO? Is it the PCM? If so anybody have a quick tutorial on how to replace, where to find a replacement?

 

When a fuel pump keeps running when you turn on the key you either have a stuck close fuel pump relay or the clock in the PCM is not running. If the clock does not run in the computer then the fuel pump will not time out after one second and quit. Also if the clock is not running the fuel injectors will not be firing so the engine will not start.
The engine would start if it was just the fuel pump relay was either stuck closed or its coil wire going to the PCM was shorted to ground.
Sometimes this may also be caused by a bad PCM ground from the NEG post of the battery or lack of power on pins 37 & 57 but this is not very likely.

IIRC on a 1991 the PCM is unplugged under the hood and then removed from the drivers kick panel. There would be a number on the PCM's plug that the auto parts store can use to get you the right one. If should start something like:
F1T*- 12A650-**.