Rear Fuel Tank Guzzling
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Joined: Mar 2014
Posts: 9
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From: Utah
Rear Fuel Tank Guzzling
I drive a 1994 F250 with the 460 engine (7.5L) that has 2 fuel tanks. I just got back from a weekend trip and I noticed something weird on this trip. When using the front fuel tank, I was able to get almost 14mpg. When using the rear fuel tank, I was only getting around 5mpg. Anybody have any idea why this is happening or how I can deal with it?
i ain't rite
Joined: Mar 2005
Posts: 65,421
Likes: 5,506
From: Marlboro Mental Hospital.
the valves sometimes stick allowing return fuel to go to the wrong tank. this will make it seem as you are using twice as much fuel as you actually are using.
try this: fill the front tank when it is at 1/4 tank mark. run it back down to 1/4 and see if it takes about the same amount of fuel, around 12-13 gallons.
now run the front tank down to 1/4 again and switch over to the full rear tank and run it until it is empty.
fill the front tank and see how much fuel it will take to fill. i bet it will only take around 6-7 gallons.
this will tell you the unused fuel is returning to the front tank instead of the rear tank.
try this: fill the front tank when it is at 1/4 tank mark. run it back down to 1/4 and see if it takes about the same amount of fuel, around 12-13 gallons.
now run the front tank down to 1/4 again and switch over to the full rear tank and run it until it is empty.
fill the front tank and see how much fuel it will take to fill. i bet it will only take around 6-7 gallons.
this will tell you the unused fuel is returning to the front tank instead of the rear tank.
FTE Legend
Joined: Jun 2006
Posts: 31,930
Likes: 1,499
From: Ottawa, Ontario
Yeah you have the fuel transfer problem. Run the front tank down a bit and take note of the fuel level, and then switch to the rear and run it for a while. Then switch back to the front and check the level, if it's more than when you first switched to the rear then the problem is confirmed.
i ain't rite
Joined: Mar 2005
Posts: 65,421
Likes: 5,506
From: Marlboro Mental Hospital.
on the newer trucks it would be replacing the in tank fuel pump that has the bad valve in it.
on the older trucks it would be replacing the selector valve.
on the older trucks it would be replacing the selector valve.
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FTE Legend
Joined: Jun 2006
Posts: 31,930
Likes: 1,499
From: Ottawa, Ontario
Yeah replace the Fuel Delivery Module(FDM) in your front tank, that contains the fuel pump and the check valves that are supposed to prevent crossflow between tanks.
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