Arrgh fuel pumps!

[RPM289]

Just swapped out front tank, pump assembly, and rear pump assembly out couple weeks ago. Was running on front tank as it had not ran in years so figured everything was new Id run a couple tanks through it. Gas mileage was terrible 7.3 MPG! As i was running it I went to fill up both tanks and could not get a drop of fuel in rear tank, figured out while I was running off front tank it was filling up rear tank at the same time! Guess check valve in new assembly in rear tank is not working. Always something! I ran rear tank down to red line and switched to front tank when I reached 1/2 tank on front I looked at rear and it is a 1/4 tank so it's pushing good bit of fuel into rear tank. At least my MPG should be better off rear tank anyway!

 

[oilwell1415]

Ford had a recall for this problem back in the day. The fix was to install a check valve in the fuel line to keep this from happening. As a result of the recall some pump suppliers do not actively try to check the flow of fuel back into the tank. Sometimes the pumps do a pretty good job of it; sometimes they don't. I'd look at installing check valves. You can still find the original Ford parts, but they are pricey. There are lots of aftermarket options as well, but they generally are not as easy to install.

 

[rusty_408]

i gave up keeping two tanks in my yellow truck. had two brand new lmr fuel pump assemblies, and both had check valves fail on the return side within 6 months. the additional check valves on the ford recall are on the supply side and do not fix this. if motorcraft still had replacement options i would put my faith in those, but now i dont trust the aftermarket options. i blocked off the front tank in my yellow truck. i may try the quantums in my white truck, but idk.