Three problems related to tank filler pipe and cap have been reported for the 1996 Ford F-150. The most recently reported issues are listed below.
Fuel tanks. Filled rear tank and opened front tank to fill it. When I took cap off gas splashed out. The front tank was over full. I talked to a Ford mechanic and he told me that it was a valve in the return line that caused the front tank to over fill from the rear tank. He also said that Ford did repair some trucks ,but wasn't doing it now.
Dual gas tanks. Gas is pressurized from rear tank to the front tank, causing a fuel transfer to the front tank, front tank is overfilling, gas is under pressure, spilling from the overflow. When the cap is removed, gas explodes from the filler neck.
When both tanks were full and the rear tank was used the fuel would leak from the neck of the front tank. Returned usps, 2nd attempt made 06/08/07 failed.