I have a problem that just started about 2-3 weeks ago on my 94 F150 5.8L on the front fuel tank. When driving on the front tank when its full if hardly does it. By 1/2 tank its becoming a problem. Driving along and it acts like its running out of fuel, It will start slowing down and wont accelerate, then bogs, and bucks if i don't do a quick flip to the rear tank and then I can and have immediately flipped it back to the front tank and it runs fine for 1/2 mile to 30 miles and then repeats. By 1/4 tank its doing it every city block. Checked Fuel pressure on day 1 both tanks engine off 40-42psi, Running engine 32-36psi, Unhooked the FPR and got 42-43psi. Day 5 on the front tank I had to turn the key on and off 3 times to get fuel pressure. 0,0,40psi. Day 8 or so turned the key on engine off and went straight to 40-42psi. Day 12 turned the key on and off 4 times. 0,0,20,40psi. Fired the truck up and checked it running, 36psi front and back. Took vacuum off of FPR and got 42psi. When I got the 0 PSI readings you could here the fuel pump running but it did not produce and pressure. I don't know if its a low voltage issue to the front tank, (Should mention the fuel gauge does not work on the front tank) The fuel selector switch going to crap, or the OE fuel pump is about shot?? . The truck runs great all the time on the rear tank. Anyone have any ideas??

 

Almost sounds like the pump is overheating when the fuel is low in the tank. If you have a multi-meter, you can check for power and ground at the pump. You can also wire up a headlight bulb to some leads and test the current capacity of the fuel pump wires to rule out bad connections.

 

That's a good possibility. I had asked the previous (original) owner how many miles can I go before I need to change tanks when I bought it. His reply was I have no clue. I just ran that tank till it ran out of gas then switched tanks. I was like What. Anyways that tank has given me 20,000 + miles of life so if it needs a pump I have no problem putting it in. Not planning on selling the truck.

I guess I need to drop the tank to check the voltage at the fuel pump. Didn't want to do that but if I need to I will.