If you know the boost pump is putting out 8 PSI in the rear than you may have a bad Selector Valve on the Frame.

 

Is the float or sending unit for gauge in this assembly or separate; my rear tank is filling the front tank also, but gauge shows empty all the time on front tank. the truck is 1993 F150 with 300 six engine and 5 speed 2wd and runs fine on both tanks other that the fuel transfer problem; I can smell strong gas odor when running off rear tank.

 

The gauge sending unit is separate.
Sounds like you have a bad FDM in the front tank.





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So if I am running off rear tank and it is filling the front I need new FDM for rear tank. Thanks for the nice picture's, it does help.

 

No then you would need one for the front.

 

10-4 on that. Thanks again

 

I have a 94 F150 5.8 that is leaking gas out of the front tank and crossfilling from the rear tank to the front. From what i gather i have a bad FDM in the front tank. The truck runs fine off of the front tank. Will the bad FDM cause the front tank to overfill and leak? Will the truck still run ok with a bad FDM?

 

jasoncrbtr,

Yes to both questions.

 

my '96 F-150 I6 is doing the same thing. rear tank is filling the front, and it sometimes wont start on the front tanks. What is the fuel delivery module? Is that a fancy way of saying fuel pump assembly? Cant find anything online for FDM. Tips for replacement?

 

Yes you can call it the fuel pump assembly.


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do you have to replace the entire thing, or just a part of it. The motorcraft pump is $450

 

No you do not have to replace the entire thing, just the fuel pump assembly.

Just this, about $150 at O'Reilly Auto Parts:


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If I can ask a question as part of this thread.... my 90 f-150 doesn't have voltage at either pump. Front tank is on the ground.... relay in engione compartment kicks on....what do i check next? I took the tank switch out but I don't know the pins to check voltage there. Where do i go from here?

 

What relay in engine compartment kicks on?
EEC Power Relay or Fuel Pump relay?



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That would be the fuel pump relay. Truck sat for two years and I am trying to revive it. 2WD, 300-6, auto.