Ford 1994 f-150 dual tank problem

Sounds like something amis in the tank,like pump coming out of the fuel, check the pick up filter screen.

It could be the tank swap switch

Sounds like the selonoid at the switching valve is not working.

Relay

check all lines and filters. berrydalewolf

You may have run out of gas in the front tank, but the gauge may have been reading the rear tank or the front sender is stuck. Is the fuel line switched electrically or manually controlled? How are the gauge connections switched?

A FORD EQUIPED WITH DUAL TANKS THIS YEAR MODEL HAS CHECK VALVES IN THE FUEL PUMPS .THE FUEL RUNS FROM THE REAR TANK WHEN IT IS POWERED ON TO A TEE AND INTO THE SAME LINE AS THE FRONT PUMP . THE PROBLEM IS AT THE BOTTOM OF THE FRONT FUEL PUMP THERE IS A CHECK VALVE ON THE FOOT AND IT IS NOT WORKING.WHILE THE TRUCK IS RUNNING WITH THE REAR FUEL PUMP ON IT IS PUMPING FUEL INTO THE FRONT TANK . IT WILL RUN OUT OF THE NECK WHEN IT IS FULL.THE FIX IS SIMPLE REPLACE THE FRONT FUEL PUMP. THEY DONT MAKE A CHECK VALVE REPLACEMENT I CHECKED I HAD THE SAME PROBLEM AS YOU.

I have to say i'm only guessing, but it sounds like the valve that switches the flow of gas from one tank to the other must be sticking part way open, or bypassing or something, and anything your engine doesn't require, is being returned to the front tank, instead of the rear.

Just in front of the side tank is the selector.Very common problem.The rear fuel tanks pump quits.

I’m happy to assist further over the phone at https://www.6ya.com/expert/joe_a3369546f8067589

Sounds like the rear fuel pump in the tank is not working and the float or sender is bad also. check to see if the rear pump is working should make a humming noise.