So I re-installed a front tank in my 88 F150 and it works. Now I seem to have a problem with the rear tank. When I bought the truck it was running off the rear tank into the inline fuel pump on the rail without problems. Now that I've got the front tank and Dual Function Resovoir (DFR)installed the rear tank doesn't seem to work anymore. I can hear the fuel pump working, it primes like it's supposed to when I turn the key to the run position and it'll idle all day long off the rear tank. Now here's the kicker, when I put a demand on it the truck simply acts like it's run out of gas. If I hit the selector switch quick enough the front tank will catch and everything runs normal. I can switch it back and within a half mile it act like it's run out of gas again. I've replaced the rear in-tank pump, cleaned out the DFR and checked it with air like the Haynes and Chilton's say to. COuld it still be the DFR or is there some electrical bug that I'm missing?

 

I would guess the rear pump is not working. You say you changed it out so I would say you have an electrical problem. This wiring problem would be from the selector switch on the dash to the rear tank plug. Most of the time this is the plug on top of the tank but could also be the switch on the dash.

Here is a wiring diagram:
http://i54.photobucket.com/albums/g9...-88FSeries.gif

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