Help!! 1989 f250 ford 7.3 diesel dual tanks....Tank fuel sensors work fine on both tanks but when I switch to the second tank fuel filter light comes on and the truck stalls with a full tank, when i switch it back it runs fine? What do I need to fix?

 

Sounds like the tank switcher is getting stuck in limbo. The FF light indicates a vacuum between the IP and FF. In short, it sounds like your switcher valve is acting as a shutoff valve when you switch to "that" tank.

 

Where can it be located?

 

the tank selector valve is located in front of the front tank. is uses a 10 mm bolt head. not sure of the thread size. i had this problem before. come to find out that i had a restriction in my lines. so i pulled off the bed because both tanks were full and i didnt want all that weight over my head. i put a piece of multi fuel fuel line on the end of the pickup tube and reinstalled the unit back it the tank. outside of the tank i used a mr gasket 12d fuel pump to lift and push the fuel thru the selector valve. i installed a fram G2 fuel filter on the inlet side of the pump to catch any trash or debris that might get collected in the tank. i did this for both tanks and wire the pumps with the selector valve thru relays. about 1 ft ahead of the selector valve i put a holey blue pump. it make starting really easy. especially if i dont switch the tanks quick enuff.

 

Thats great info but I just want the second tank to be useable again...in lamens terms what can I do?

 

Bring it to a garage.lol

 

Most likely the fuel selector valve is FUBR, and a plug and play one is a Ford only item, and they are spendy. An after market one is available, but the wiring is different, and it needs to be rearanged at the plug. Someone has done this and posted the wiring lay out for doing this. You could remove all the fuel lines from the valve, from the tanks and to the engine, and blow air threw the top fuel line ports one at a time to see if the valve has some crap in it, then switching the valve to the other tank and doing it again. It might dislodge the blockage, and it would just cost you your time. Most likely the valve is shot though.

 

i still use both tanks. i have a pump and filter for each tank i can upload a pic and draw up a wiring diagram for ya if you need it.

 

That would be great...more of a summer project for me...I really want to band aid it to get through winter for now though.