1994 f150 fuel issues

fredfredburg · Dec 31, 2023

Been having the issue with fuel pressure and tanks overfilling the unused tank. Pretty sure I need new fuel pumps as some valves are probably clogged in them. But for the life of me I can’t figure out/find the pump for my front tank. Quick google said my tanks are 16 and 19 gallon but can only find 17+ on rock auto. Going to take tanks out and clean because truck has been sitting a year+ after previous shops couldn’t figure out the issues. I’m assuming the pumps they replaced were broken when delivered and didn’t think that was possible but lots of reading is telling me that happens a lot with these models.

First time posting any suggestions is welcome. This is going to be our daily driver so while I have the bed off anything I should check/replace.

also don’t want to go off of part numbers on the current pumps because I don’t have the original pumps after the shop failed to fix idk if the correct pumps are even installed.

YooperDave · Dec 31, 2023

Sounds more like a selector valve problem than with the pumps.
Also could be a clogged return line.

fredfredburg · Dec 31, 2023

Thank you for replying. I don’t see how a clogged return would cause one tank to fill the other and the diagrams of the pumps they are supposed to stop the extra gas through multiple valves. Found some forum posts and videos where pump replace my does the trick. My biggest issue right now is not being able to source a pump for the front tank. Do you think the selector valve may be feeding the return into both tanks? But then I’m still lacking pressure to the engine.

YooperDave · Dec 31, 2023

Selector valve can easily cause both issues (low pressure and filling the unused tank) from an internal leak between the 2 sides.
Reason I mentioned a clogged return line is the selector valve controls that too, and if one line is clogged, it could damage the valve and send the fuel down the path of least resistance.
I would check the return lines to both tanks, then test the selector valve and replace if necessary, and likely being the original at 30 years old, probably would be a good idea.

I'd also test the electrical connections and grounds while it's apart. If those aren't grounding right or not getting enough voltage, that will cause problems like that as well,
though I'm thinking the selector valve is either leaking or just not switching all the way.

1994 f150 fuel issues

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