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1992 Ford F-150:
Problem Switching Dual Fuel Tanks

Alex Steele
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as seen in Truck Trend



I just bought a '92 F-150 with dual tanks. The truck was undercoated from the factory, so the undercarriage is in excellent shape.


The problem I am experiencing is when I switch from the front to the back tank, the gauge switches to indicate a full tank like it should, but within a few miles the gauge reads empty and the front tank reads full. Also, the truck begins to act as if it is out of gas.




The problem has to be, or at least related to, the fuel tank selector switch. This guy does all the work. When you're in "front tank mode" the selector switch sends 12 volts to power the electric fuel pump in the front tank. At the same time it connects the fuel gauge sending unit in the front tank to the fuel gauge in the instrument cluster. When you select the rear tank it does the opposite, and hooks up the pump and sending unit in the rear tank.


It sounds like there may be bad contacts within the fuel tank selector switch causing you grief. If it's acting up on a regular basis get it to a technician. It should be a quick confirmation with the appropriate wiring diagram and a digital volt/ohm meter.


Here's a little trivia on a somewhat relative recall pertaining to '90-'93 F-series trucks equipped with dual tanks. There was an issue with an internal check valve within the fuel pump not working properly. This would allow fuel pressure to "cross-flow" to the tank containing the bad check valve, which could eventually cause fuel to actually overflow out the fuel filler cap -- not fun.


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Ford | Fuel Tank | Wiring/Circuits
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10 Oct 2018, 17:59
RE: Dave, I can only answer the question on what you are telling me I am not there to see the problem happening so these are just educated guesses.

Check your fuel pressure, your pressure regulator may be malfunctioning causing a higher than normal fuel pressure which can cause fuel injectors to leak causing a higher RPM. Check the engine for any vacuum leaks they can also cause a higher than normal Idle.

There is a problem with the fuel pumps and the check valves inside them. You may want to check into this. I read that both fuel pumps and external check valves may need to be replaced
10 Oct 2018, 15:32
Had this problem and disconnect the front tank. Since the problem occurs it has an idle of 1500 rpm.
Simon navarro
12 Apr 2018, 22:49
There was a ford recall for a modification on the dual fuel tanks. The problem was fuel returning to the wrong tank because of a one way check valve in the pump. The mod. Was a check valve installed at each tanks return fuel line. I haven't been able to locate some that are priced reasonable. E-Bay has two for 240.00 . I'm just going to buy a flairing tool and make my oun lines for one tank and to Hect with ford. Good luck yall.
28 Oct 2015, 10:13
no you must take off the light switch pull
26 Apr 2012, 18:46
If you're referring to the check valve within the fuel pump? You must first remove the affected fuel tank in order to replace the pump.
Boba Fett
23 Apr 2012, 15:18
Must be the check valve on my 1992 F150
How do I replace?
19 Apr 2012, 18:40
Not quite sure what you mean, but you should check the service manual (your specific model) for correct remove/replace procedure for the switch.
alan jeter
16 Apr 2012, 16:50
I am replacing the gas toggle switch in the dash does the black trim pry off with out having to remove the light knob or anything else?


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