Hi,

The pumps at times will function what appears to be normal. At other times the pumps will not stop running and it is at those times when the engine does not like to run.

I do not know if the engine will not run due to too much pressure or not enough fuel pressure.

The problem is with both tanks and pumps so I do not believe the problem is inside either of the tanks.

One problem is that I just got the truck and the prior owner had at times done a little work and you know how that can be a problem. He could have done some damage to some hoses or who knows what. He had replaced the radiator and the left side exhaust manifold recently, though at different times. He thinks the problem started around the time he did the radiator. I know it dosn't make sense but things can get bumped or damaged.

What would the problem be that it could come and go?

I drove it for a few miles and I thought that maybe the problem had gone away after I replaced what appeard to be a short vacuum line by the throttle body. But the problem still comes and goes.

Now the truck is stuck till I figure the problem out.

Suggestions on a this inconsistent problem?

Thanks!

 

Do both pumps keep running simultaneously when the engine is shut off or does whichever pump is selected keep running?

If it's both pumps at once then something in the wiring has been seriously FUBARed. If only the selected pump keeps running it sounds like the fuel pump relay is sticking.

 

If the following three things occur at the same time:
-Fuel pump runs as long as the key is ON.
-Engine runs rough, or will not start.
-You can't communicate with the ECM (you can't get any codes at all)

Then the ECM needs to be replaced.

 

Thanks for the replys.

At times they will function properly.

ECM? Is that the box down by the drivers kick panel? I saw that one and I know there are at least two more boxes up kinda behind and to the left of the radio.

I have not tried getting the codes, do not have a code reader. I am going to try and get a friend over to read the codes.

Only the pump selected will have the problem. I will try the relay and see if that helps. I tried swapping in the relay from my 1991 F250 but the contacts were different. It fit but it had one less contact than on the F150. The problem was the same.