Has anyone had this problem.I have a 1995 F150 5.0L engine with automatic trans with front and rear gas tanks.I get 13 MPG on the rear tank and 18MPG on the front tank at 60 mph.I'm scratching my head on this one.

 

same thing happens on my I6. 17 front tank and 14 back. everytime! weird!!

 

Are you calculating it right?

Granted your speedo/ododmeter are accurate and the dual tank set up is working properly, try this: Fill up one tank until the pump shuts off automatically, stop pumping. Do the same the to the other tank. Reset trip. Drive until its time to refuel. For best results, use the same gas pump and repeat the fill up. Now take the miles driven, and divide by the gallons just pumped. There's your overall MPG.

Then try one tank at a time to see if the numbers match up.

That works on single tank cars, and I would assume it would work on a dual tank set up...

 

No mystery.. you both have the fuel transfer problem between tanks. Change the FDM on the tank that gets the best milage but keep the fuel pump for a spare.

 

I tried the calculating thing a few times and each time I get less MPG on the rear tank.BTW the rear tank pump was changed by the Ford dealer about two months ago because it quit but I had this problem before that.They also checked to see if the rear tank was transfering to the front tank.

 

Then that means your problem is with the front tank and it's check valves, fuel transfer is the only way milage could be different on each tank.

 

Where are the check valves located?

 

The check valves are integrated into the FDM(fuel Delivery Module).. that's a plastic resovoir around the pump inside the tank. It comes apart with a little work so it can be changed without buying a whole new assembly.

 

wow. i think i'll use my front tank only for now. i will put that one on the list though.