One day as I walked past my truck which had been parked for about 6 hours I smelled gas and found a puddle and it was full under the fill cap, I never fill the tank that full. I was running on the rear tank at the time. What does anybody thank could be the cause?

 

sorry forgot some important stuff
1987 F-150 w/300 EFI

 

https://www.ford-trucks.com/forums/s...d.php?t=341697

 

The check valve between tanks is faulty causing fuel not used by the engine to be returned to the wrong tank. Ford has a free fix for this (TSB) if the time frame or mileage has not been exceeded. You have to specifically tell the dealer that the front tank is overflowing from the rear tank, otherwise they might not want to fix it under the safety recall. I got two new fuel pumps out of it and a check valve. Good luck.

kwing

 

I experienced a similar problem with my Ford's dual tanks. kwing suggested a possible recall on the fuel pump and went to the dealer to confirm. They confirmed the recall but it wasn't my fuel pump causing the high pressure.

In my case, the charcoal cannister under the hood was leaking. I changed the fuel filter and voila! the leak, or high pressure, disappeared.

kalamazoo

 

kwing, Do you think that the check valve is the same problem with my 87. I was surfing other posting and it seem that the older models it might be the tank selector valve used to shift between front to rear tanks.