trimmers

Hi folks, Dan here and new to the forum. I am hoping someone can help me out with my grandfathers 1989 F 150. The basics: It is a V8, 5 Spped manual, standard Cab, XLT Lariat. The truck will not receive gas from the fwd fuel tank, this is a new issue. It always worked before but has sat for a few months. I figured maybe the pump motor or a fuse, but a larger issue has started as well. While running off of the rear tank, the fwd tank is over pressurizing and pushing fuel out of the fuel cap. I noticed it at stop signs and when parking. The cap is very dangerous to open to release the pressure (it wants to spray fuel all over the place). Is there is valve that might be stuck that works when the operator switches tanks or something? Any help on this would be greatly appreciated. Thank You, Dan

techrep

iTrader: (1)

Your rear tank is pumping it into your front tank...need a fuel pump

trimmers

Is there a one way check valve or something in the front tanks fuel pump set up that stops this over-pressurizing?

techrep

iTrader: (1)

Does your front tank work properly ??

trimmers

No, it wouldn't deliver fuel yesterday. I get what your saying. I do realize the rear tank is pressurizing the front tank. I just want to know how it happens. I figured a valve or something must be stuck or maybe in this case, the fwd pump is bad and allowing fuel to pass by it and into the tank while operating on the rear tank. I need to be able to explain why and how to my grand father so he will aloow me to fix it for him.

FLHRC7

I had a problem with my gf's 1989 F250 Lariat where only one tank was working. It ended up being the vacuum operated valve assembly (cannister) that is common to both tanks. This valve assembly transfers the fuel path and recircs fuel back to the selected tank (as far as I can determin). Each tank has its own fuel pump and there is a common fuel pump on the frame rail below the drivers side door. When a tank is selected, the common pump runs as well as the selected tanks pump. This forces the correct path through the valve assembly (all mechanical, no wires). Thought it was a bad fuel pump but I was able to hear the individual pumps running. By disconnecting respective fuel lines, I was able to figure what was working and what was not. It was still a guess when I replaced the valve assembly/cannister but it now works as new. Don't know if this is causing your issue but it is common to both tanks. Good Luck

2010 F150 Platinum Screw
5.4 Black

trimmers

That is where my first look went. I followed the lines and saw this canister (common component to both tanks). I figured something in the canister must be stuck or something. I already dropped the fwd tank since i last posted because i want to fix the sending unit anyways. Thanks for the tip. I'll prob just replace bothe, the pump assy and the canister and button it up. Thanks man

techrep

iTrader: (1)

Easier to pull the bed off that to drop the tank...I guess that's too late. Good Luck

Just call me Sean

iTrader: (1)

That's called the dual function reservoir. If the low pressure tank pump has lower pressure than it's supposed to then it doesn't have the pressure to move the mechanical valve in the DFR which results in crossfilling. Or it could be bad too.

FLHRC7

Yes..... the DFR (not valve assy/cannister). Thanks for the correction, I couldn't remember the name. Growing old ain't for sissies. Chances are your DFR may be okay. Easy enough to replace after you try with new sending unit.