Fuel system issues continue
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5th Wheeling
Joined: Jul 2023
Posts: 29
Likes: 2
Fuel system issues continue
Hey all. 89 F250 7.5 L the usual dual tank issues. So... been having fueling issues for a while, front tank full but cant access it, new dual action valve, front tank works for 3 min, truck wont run at all any more, clean sand out of valve, rear tank works front does not, bypass dual valve for rear tank, front still hooked up, rear tank pumping into front tank overflowes onto road, me not happy wasting precious gas. remove valve hook up rear tank only works fine. remove front tank, full of rust, fuel pump leads corroded off. Had ordered sender and intank pump as gauge always said full anyway. drove to town to fill rear tank, switched to front just to see what it would do - remember tank is on the ground at my house, drove 20km to and from town switch on front tank, still ran fine. so switch isnt switching tanks although it swwms to be switching fuel level gauges. Front tank still shows full even though its not in the truck. What now?? Could there be an ecu issue?
Cargo Master
Joined: Aug 2021
Posts: 2,258
Likes: 742
From: Maryland
Start with the advice in the second post of your original thread https://www.ford-trucks.com/forums/1...-problems.html.
The Dual Function Reservoir (fuel tank selector valve) works off of the hydraulic pressure, from the in tank fuel pumps.
The in tank fuel pumps need to supply proper pressure to the Dual Function Reservoir and the gasoline needs to be clean. The Dual Function Reservoir won't tolerate sand or debris.
Once you establish that both fuel pumps are delivering clean fuel, at proper pressure, to the DFR, then move to testing pressure on the return side of the DFR.
You've got to be methodical in testing this system.
The Dual Function Reservoir (fuel tank selector valve) works off of the hydraulic pressure, from the in tank fuel pumps.
The in tank fuel pumps need to supply proper pressure to the Dual Function Reservoir and the gasoline needs to be clean. The Dual Function Reservoir won't tolerate sand or debris.
Once you establish that both fuel pumps are delivering clean fuel, at proper pressure, to the DFR, then move to testing pressure on the return side of the DFR.
You've got to be methodical in testing this system.
Cargo Master
Joined: Aug 2021
Posts: 2,258
Likes: 742
From: Maryland
My guess is that fuel is being siphoned from the rear tank, then the frame mounted, in line pump is pulling from the rear tank.
I know that when you disconnect fuel lines at the DFR, fuel will siphon indefinitely.
But, that's just a guess. I don't have experience modifying these systems. I've done a fair amount of troubleshooting and installation on complete systems.
I know that when you disconnect fuel lines at the DFR, fuel will siphon indefinitely.
But, that's just a guess. I don't have experience modifying these systems. I've done a fair amount of troubleshooting and installation on complete systems.
Hotshot
Joined: Jun 2015
Posts: 12,872
Likes: 2,445
The rear pump not turning off is a problem. That could indicate a problem with the selector switch not turning off power to the rear pump and supplying power to the front pump.
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