I have a 1993 F-150 5.8L 4x4 and when i use to the rear fuel tank the truck can start and idle decently, but when i step on the accelerator it starts to sputter and act like its fuel starved (the effect magnifies the more i press on the accelerator). The truck runs perfectly fine when i'm using the front tank though. From what i can find it seems the truck only has one fuel filter that filters both tanks so i doubt its that since the front tank works fine. My guess is the rear sending unit is weak or clogged up?

Im guessing on this one however so any help would be appreciated.

 

I also considered it may be water in the fuel tank, so i added some fuel stabilizer that supposedly gets rid of water but i had no change in performance.

 

Could be the tank selector valve. Otherwise, I think you're on the right track. I believe there is a filter on the stem of the sending unit for large particulate junk. Might check that.

 

There is no selector valve.

 

Quit guessing...rent a fuel pressure tester. Verify fuel pressure on both tanks at idle and under load. 30-35 PSI at idle, 40-45 PSI under load.

 

Where can you rent a fuel pressure gauge? does auto zone rent them?

 

More info... When i turn the ignition switch on (using the front tank) i can hear the fuel pump clearly. When i do the same with the rear tank selected i can barely hear the fuel pump at all and it only makes the sound for about a 3rd of the time that the front pump does.

 

I tested the pressure and front tank is normal 38 psi idle and 40+ ish under load.
I switch to rear and it idles at 26 psi peak and spuds lower often... and when i accelerate it drops way down to below 10 psi and it sounds kinda like its sucking bubbles and air when i put my ear close to fuel intake. Any suggestions yall?

 

Could be a bad rear pump. These trucks have a high pressure pump in each tank. Each Fuel Delivery Module has a check valve to prevent the running pump from back filling the unpowered tank. This internal valve is known to fail which causes the unused tank to fill up with fuel.

The other side effect is it can cause low pressure from the good pump because the running pump is providing fuel to the engine while it is also filling the other tank. Make sure the front tank is not filling up with fuel from the year. If it is not "gaining" fuel level then you most likely have a bad rear fuel pump.

 

Yea I have not noticed any cross filling of either tanks, of corse i cant really run the rear that long because its too low pressure to really drive on. But i ordered a new fuel pump for the rear so ill let yall know how it works out after i replace it! (fingers crossed)

 

After fighting some welded bolts and nuts i finally was able to change the fuel pump and clean out the gas tank and popped it back on, it runs great now! 34 gallons of gas at my disposal

 

Great news. Thanks for the reply back.