why can't I switch from front fuel tank to rear fuel tank?

Typically, the selector valve on the frame just below the driver's seat has failed. I've been looking for a good aftermarket replacement for my '87 F-250 some time now but fear that I will have to bite the bullet and change out all of the OEM stuff - wiring and all.

If it's diesel, it could the selector valve, the fuse or the switch on the dash. If gas, could be the fuel pump/sending unit.

Need wiring for 1989 Ford F-150 duel fuel please help

Your fuel tank switch in dash has six wires red wire must be hot. And when you switch it the red power wire activated the front or rear pump. Drove me nuts. Now both tanks work properly.