ncAGteacher

I have a 91 xlt 5.0 with the dual tanks.

Problem: When you run the front tank it pumps fuel to the rear tank

I have been told there is a fuel filter of sorts between the tanks that is clogged. Not finding any such listing I am thinking it is some kind of cartridge/canister of some type and I just have to figure out what it is called to I can secure the correct part and replace it. Anyone know?

TIA

sodapop6620

The first question is how long have you had this truck? And how long has this issue been going on for?

It sounds like the tank switch is not switching the return line to the front tank. This may have some debri in it or just may not be switching.

I hope this helps.

ncAGteacher

I have had the truck since May. It was my late FIL's truck and I have no clue if this was an issue before as the front tank fuel pump was bad and he had been just driving off the rear tank. I replaced both fuel pumps in October and this has been going on since then. I just have been dealing with it but its kind of getting annoying and I decided to seek out some solutions to fix the problem.

Thanks

MONSTERPRE

if you replaced them yourself and didn't put the lines back together properly, then it only makes sense that the fuel lines under the bed are installed wrong.

MONSTERPRE

It's my understanding that the return line only goes to the front tank, not both. I'm not sure about that year of truck though ......IM WRONG ABOUT THAT.

Grey line=return line
Blue Line=delivery line


if that's the case, then you have the lines switched on the front tank. The Return Line can only deliver fuel to the tanks and not to the rail...therefore the pressure would be diverted from the front tank to the nearest relief(rear tank)......Anybody agree with that?

benbailey84

i dont think that is true on an 89. I fill up both tanks every other week and use them before i fill up. i swap out what tank i use first after a fill up each time i fill up. The front tank is larger than the rear or other way around, i dont remember exactly, but anyway back to the issue... there is a strainer in the select valve that may be clogged up... i dont remember where i saw it but there was a write up on that selector, do a search on it and you will find it...

ncAGteacher

thanks, will look into that tomorrow

flareside_thunder

I agree with the tank selector valve. My 95 has the same issue. On another note. My wife is an Ag teacher and FFA adviser here in Florida.

MONSTERPRE

my 1994 dual tank f150 does NOT have that valve...when i switch tanks at the dash it engages the fuel pump inside the tank. The two lines that come out of the top of the tanks are directed to the charcoal box in front of the passenger front tire, then into the throttle body...emissions.

Nitehawkjr

A 91 will not have a selector valve it changes from pump to pump at the selector switch. The pumps in each tank have a check valve in them to keep the tank from backfilling when running off the other tank. Ford also installed check valves in the lines to help with the backfilling issues that are common with these trucks.
The fittings in the top of the tanks are vapor check valves the hoses that come from them go to the charcoal canister.