'94 F-150 4.9 300 XL Extended Cab.

SYMPTOM. With both fuel tanks full, when running the rear tank, the front tank overflows, and vice versa.

SUMMARY OF CURRENT THREADS. The '94 with dual fuel tanks does not have a fuel tank selector valve (like prior year models), but rather each fuel pump assembly should have an internal check valve that will close when the pump isn't in use to prevent the return line fuel from going back into the tank that isn't in use. (Ford did for a time, as part of a recall not related to the 94, provide check valves that were installed between the fuel line and the fuel pump, but those are not widely available). The fuel pumps should simply be replaced to resolve this issue because the fuel pumps should have the check valves built in. To verify the check valve is working before installing your new pump, blow throw the return line (if air comes out the other end, the pump either has a defective check valve or doesn't have a check valve). See this video:
MY PROBLEM. I replaced both my fuel pumps: Delphi 10262 (rear tank) and Delphi 10265 (front tank) from RockAuto. I now have crossfilling both ways. My assumption is that the pumps I installed do not even have a check valves in them. I wish I had known to blow into them to verify the check valve worked.

QUESTION #1. Has anyone recently purchased a fuel pump that did not produce my problem? I would be grateful if you could link it so I can buy it and be done with this.

QUESTION #2. If the aftermarket pumps don't have check valves, it seems that the manufacturers are basically telling us to rely on inserting an aftermarket fuel selector valve into our fuel system, like the one here: More Information for STANDARD MOTOR PRODUCTS FV5 (rockauto.com). As noted above, the '94 did not come with a selector valve, but one like this could theoretically be installed on the fuel rail between the fuel filter and engine, as outlined in their instructions here: GF5642-4REV.pdf (rockauto.com) (though I am not sure that is possible). Has anyone gone down this path or have any input?

Thanks,
Mike

keywords: gas overflowing fuel leak rear tank pump front tank dual

 

I have replaced the pumps in my truck several times. I've used Spectra pumps and Carter. I have not had a cross over situation. The Spectra pumps are hit and miss on quality. I just put a Carter in a few months ago and it seems fine right now. But I wouldn't be surprised if the same company makes them. The Carter was just a pump, the Spectra's have been with the hanger assembly.

 

School called and said there was a puddle of gas under my son's truck; I told them don't let the kids smoke near the truck. ’96 reg cab short bed. 70k miles. Two new fuel pumps. New selector switch in dash. With both tanks full and selector on front tank, start the truck - fuel overflows out of the rear fill nozzle. Switch to the rear tank and fuel overflows out of the front fill nozzel? Maddening! Any suggestions are greatly appreciated.

 

Did the whole pump and assembly get replaced? If it's just the pump, I would guess that the hanger assembly is bad, or it was not installed correctly, or someone crossed the return lines. Just kind of guessing but that is what I would check.