If I remember right this is a recall on the fuel pump itself, My 91 F150 had the same problem, also when you would fill both tanks and drive on the rear one first, it would over flow the one nearest the driver, this is because a bad fuel return system design.
I beiieve it was code 642. The fuel poump is not the problem. It works . I ran a hot wire to the power wire for the pump so i could get it home when it first happened.I still drive it that way today.But i only can use the back tank.I never hotwired the front tank.
Click my black Bronco in my signature & read the captions in the '90-96 Fuel System album.
The pumps are supposed to stop ~1sec after the key is turned to RUN, if the engine is spinning LESS than ~150RPM.
That code means that the EEC pin 8 doesn't read ground after the EEC turns the FP relay OFF, which suggests a bad wire from the EEC to the FP wire, or from that splice to the FP. 543 would mean it doesn't read hot when the FP relay is ON, which would suggest a bad inertia switch. Exactly where did you tap your hot wire into the circuit to make the truck run? Check from that point FORWARD toward the tank switch & inertia switch.
I tapped into the fuel pump wire about halfway down the frame rail. Ihave also had a problem with my parking lights not turning off. They come on whenever the truck is started ,whether the light switch is turned on or not. I have to disconnect the battery to turn them off. They stay off until the next time I start it.
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