1990 Ford F150 dual fuel tanks

Asked by Nov 21, 2016 at 02:50 PM about the 1990 Ford F-150 XLT Lariat LB

Question type: Maintenance & Repair

I just bought a 1990 f150 xlt lariat. Currently the truck is pulling from the
rear gas tank. When I switch to the forward tank, the needle on the gas
gauge gets pinned way past full and the truck dies, as if it just ran out of
gas. When I switch back to rear tank, truck runs fine.  Does anyone have
any ideas what could be wrong with forward tank. It appears as if the
selector switch is functioning fine.

8 Answers

It seems that it has a Fuel pump issue. In all actuallity, it seems as though the pump may of been taken out or completely unhooked from functioning. If the pump for tank 1 is disconnected from power, the needle will jump all the way up!!


Check the wiring plug to make sure tank front tank is connected, if it is, you'll have to remove it and inspect the fuel pump assy

Thanks for your quick response Thomas and lrodri911. I'll check the fuel pump connection. Is it mounted along the frame rail?

I have a similar issue and the problem isnt the fuel pump its the selector valve getting stuck it dumps all the fuel from the rear tabk into the front causing it to over fill be warned if u try and loosen the front fuel pump or which ever is pinned over full about 3 gallons of pressurized fuel will spew all over you i took a shower in gas .... be warned if your a male and your tank sprays you your area down below will burn and smell of gas for about two weeks. Anyways im trying to locate a way to make it run off the front tank only . Any clues ???

And dont drive with it pressurizing the front tank if the seals fail while driving it sprays on hot exaust and causing explosion and or fire.this is per a certified ford mechanic

Mine is pulling gas from the front tank only and shuts down when I switch to the rear tank. I'm told it might be a wiring harness issue? It is not engaging when the tank switch is flipped. Is there a part number of proper name for the right part?

Mine ended up being a bad fuel pump. Replaced the pump and now it can pull from both tanks.


there is a recall for the rear tank pumping to the front.i had it done for free at ford.

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