I have a 93 F150 with the I6 motor. Presently it acts like the fuel pump has gone bad. Before you could hear what sounded like the fuel system was building pressure (a whiring noise) then it would quit and then the truck would start. Now I just hear the noise and it doesn't stop. Truck has the dual tank setup and it is the front tank that is the problem rear tank quit working a long time ago and I haven't had the time to really fix it. Hopefully, this is something simple not looking forward to dropping the tank.
Any ideas or suggestions would be appreciated.

 

Haven't had this problem but would check all wiring going from the computer to the fuel pump. Make sure you don't have any wires shorting out.. Tank isn't as bad as you think though. Dropped multiple of them. Give 45 minutes at worst to get the thing out, fuel pump takes a couple minutes to replace assuming your grommets are in good shape. I do recommend putting a piece of rubber such as a tire inner-tube piece between the tank and the support arms that go under it. That is the most common place to rust your tank out from what I have seen. At that point, might as well screw your bank account and get yourself a new tank too haha.

 

the fuel pump running continuously when the key is in the run position suggests a possible computer problem.
try pulling codes; if it wont display codes, that is another clue pointing to the computer.

 

X2....continuous running fuel pump(s) is a classic sign of a failed PCM (computer).

 

I'm not as familiar with the fuel system on the later models. But shouldn't the pump cut off initially after building pressure? What if it's not building pressure, because the pump is bad? It would just run until it burned up.

Alvin, you hook a fuel pressure tester up yet? That's where I'd start.

 

No, the circuit is not designed that way. The computer is programmed to trigger on the fuel pump relay for 1-2 seconds whenever the key is cycled from Off to Run. It's strictly a timer, no fuel pressure feedback whatsoever.


Take a look at the date stamp on this thread.

 

Didn't notice the time, since he made a recent post about the same thing in the inline six forums. Figured it was better suited here so replied to this one after reading.

So Back to the fuel circuit. I assume if that's the case that the computer also keeps it on while cranking? Also, what makes the pressure for the injectors if fuel just runs back to tank.

 

You are correct. Every PIP pulse resets the timer to keep the fuel pump relay energized.


The fuel pressure regulator is mounted on the output/return side of the fuel rails. That's where the pressure is regulated to ~30-45 PSI (V8 gas engines) depending on load/manifold vacuum.

A diagram from Subford:
Attachment 277308