1993 Ford Truck 1993 Ford F-150 Dual Tank

DUALFUEL

MEMBER
1993 FORD TRUCK
V8
2WD
AUTOMATIC
109,980 MILES

Our F150 has dual fuel tanks. A few weeks ago, when both tanks are full, if you put the tank selector switch to run on the front tank then both tanks empty equally. If you put the tank selector switch on the rear tank then the rear tank level goes down fast and the front tank fills up with fuel. No engine performance problems and I took the truck in for the fuel tank recall about 8 or 9 years ago. No problems like this before now. What could it be?

Monday, December 8th, 2008 AT 12:28 PM

1 Reply

DAVE H

MECHANIC
13,384 POSTS

In a 2-tank system, sender assembly handles switching of high pressure fuel through internal valves. Should one tank overfill during use (return line returns fuel to wrong tank), pump and sender unit in overfilling tank need replacement.

Mechanical Selector Valve
A driver-operated selector switch controls selector valve for switching fuel supply from one tank to another. This valve switches fuel supply and return lines from one tank to another in response to fuel pressure from in-tank pumps acting on its actuating diaphragm.
The diaphragm switches tank connection when less than 2 psi of fuel pressure is acting on upper side of front tank and lower side of rear tank. Valve function depends upon proper operation of in-tank low pressure pumps. In all dual-tank vehicles, excess fuel not used by engine is returned to same tank from which it was pumped.

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Monday, December 8th, 2008 AT 12:43 PM