I have a 1997 Ford F-350 with the 7.5 liter...

When I run it on the rear fuel cell it will transfer the fuel to the front fuel cell while I am driving... If the front fuel cell is full when I run it on the rear cell it will actually over fill the front tank and the fuel will run onto the ground while the truck is running.

Help, anyone?

Red 5

 

you have a bad fuel pump which has a built in check valve that has gone bad. I had the same problem on my 96 F350 CCLB 4x4. Change both pumps and be good. BTW the tank that is filling is the tank with the bad check valve.

 

Thanks Rockdawg,

I will do that...

 

I had the same issue on my '89 F250 and the problem was the fuel tank selector valve was not right. Depending on which tank is selected that particular fuel pump applies pressure to the valve. Mine trouble started with when I changed tanks one day and the truck died. I thought the fuel pump must have been bad so I switched back to the rear tank. Then the rear tank started pumping fuel into the front tank to the point that when I removed the front tank fuel cap gas would spray out at me. Shortly thereafter, I tried switching back and on the tank switch and it got to where the truck would not run at all. A check of the fuel lines after the fuel tank selector valve showed no gas going through the valve. Popped the lines loose on the tank side of the valve and both pumps were pumping great. Spent the $140 on a new valve and all is good.

 

in 97 the truck does not have a selector valve, instead each tank has a fuel module unit (FMU) that contains the pump, sending unit and backflow valves and they are simply energized individually to pump fuel and open the return valve. the FMU is for the most part not serviceable though I am sure that there are those who could.