dual fuel tank problem
 

Hey everybody i have a 87 ford f250 custom and it has the dual tanks. i filled both tanks and run the rear tank and the needle doesnt move, i switch to the front tank which was full and i have only been running the rear tank and the front tank is at half empty. while the rear tank hasnt used any fuel. any suggestions?

Each tank has a seperate float level sender inside it and both of yours are messed up.

Well if i try to fill the rear tank it doesnt take any fuel. while the front will take about 5 gallons. so its not a float issue.

So I'm hearing that when using the front tank, the gauge says half full. And when running the back tank, the gauge wont read at all. Correct?

Or else you're saying that regardless of the tank your switched to, your truck only uses fuel from the front tank??

correct it only uses fuel from the front tank. could it be a bad selector valve and the high pressure fuel pump is just sucking it out of the front because the selector valve is stuck on the front tank?

Bypass Valve. Fords are really bad about it, whats happening is while you are using the front tank it is also pumping fuel into the rear tank, basically filing it as you drive

that would explain why there is gas coming out of the rear tank filler neck when i park.
where is the bypass valve?

It is attached to the front fuel pump

ok well here is the weird part. last night i had my neighbor helping me and he is a big time nerd when it comes to wiring and diagnosing electrical problems. we were getting power to which ever tank we selected. The funny part is that you cant hear the fuel pumps. so im getting power to the rear tank when its selected and it shuts the power off to the front tank but the front tank is the one having all the fuel used up and the only valve after the fuel tanks is the selector valve or "dual tank resivor valve".

Dual Function Reservoir:
http://www.supermotors.net/getfile/6...nreservoir.jpg

Info on both styles: 1983 Ford Bronco '84-89 Fuel Reservoirs pictures, videos, and sounds | SuperMotors.net


The cross-flow issue you are describing is VERY common on this vintage truck.

There is no Bypass Valve. I assume you are referring to the Dual Function Reservoir?

ok thanks its just weird how no mater what position the switch on the dash is in (front or rear tank) it only uses fuel from the front tank.

The link I posted above describes how the reservoir works. More than likely the switching valve is stuck in one position.