Have a 1989 F150, 4wd, 6 cylinder Pick UP. I recently installed a front fuel tank with pump and sending unit.


Took a ride and noticed unusual fuel consumption. Scratched my head and did a lot of checking. Kept refilling the front tank.


Today I came home and noticed that there was gas leaking from the fuel inlet of the rear tank which I was not using. Fuel gage of rear tank reads empty so that is a problem needing fixing later.


Why is the fuel being transferred to the rear tank? Other than the gage sending unit, there is nothing wrong with the rear tank that I know of.

 

sounds like a bad fuel delivery module

 

1989 truck has a dual function reservoir instead of individual high pressure in tank pumps with the associated valves inside the tank.

Fuel transfer is caused by a defective DFR.

 

My 1989 Ford truck has fuel pumps inside the tank and one on the drivers side of the frame.

 

Exactly. ....and a dual function reservoir that controls fuel flow. That's why I am saying the issue is not a bad Fuel Delivery Module (FDM) inside the tank. If your truck was a 1990 and later then I would agree that would be the cause (bad FDM).

 

There must be a selector module of some sort on the outside of the tank. Could that be the problem.

 

Dual Function reservoir...

courtesy of Steve83


Fuel Diagram (gas engine):


courtesy of Subford

The frame mounted Dual Function Reservoir is identified as the Mechanical Selector Valve/Reservoir in the diagram above.

 

That's what I'm talking about. thanks