i have a 85 f150 with the 4 speed and the 300ci 6. it has the dual tank option, but when i put the selector switch on to the rear tank the gas guage goes to empty and the truck dies out even though it is full of fuel. the truck runs fine and shows gas in the front tank postion though. i have no clue whats going on.

 

I have the same problem with my truck, I believe the pump is bad. I have a pump in each tank. The rear one is bad. Might be the same with you.

 

hmm, there is a electrical pump on carbbed trucks? but i still dont get why the guage goes to 0.

 

check your fuses then check voltage on the sending unit see if you have power.

 

will do, i will see what i can find.

 

My 86 had the same problem its probably the fuel selector valve.
I had one other symptom it was leaking from the fuel selector valve.
Its a small pump just behind the front tank it has 3 ports 2 in 1 out. A little solenoid will switch from front to rear if the pump sticks it wont switch. or it will stick and do what mine did SNAP.

I only found one source for this part Your Local Ford Dealership its about $98

Yeah its a pain mine broke 1 week before I left for college

 

does that valve also control the gas guage?

 

hi, guys. new user. 89 f150 4x4 300-i6 efi t18 manny 8.8 w/3.55s. great website. i'm not sure if the 85 is configured the same as the 89 but if it is i believe there is a module in each gas tank that consists of a low pressure pump and a sending unit (fuel gauge). just ahead of the front tank on the driver-side rail is a selector valve that switches to whatever tank according to whichever low pressure in-tank fuel pump is pushing on it (the selector switch on the dash selects only which in-tank fuel pump is given juice). ahead of the selector valve on the same rail is the high-pressure fuel pump. from there the engine. return line goes back to the selector valve to be directed to the originating tank. if your in-tank pump is fried i believe that kills the circuit for the sending unit as well, but i'm not sure. again, i don't know if the 85 is put together the same as the 89. if its an in-tank pump i'm told you must replace the whole module.

 

the problem is that your car is fuel injected and i have a carburettor. you need higher fuel pressures (35-45 psi) and carbs use way lower pressures (5-10 psi). so i would think alot of the things are different.