1994 F150 XLT 5.0L Auto -- 168k Miles

Hello, all!

The truck sat for quite awhile getting some "here and there" time spent on refinishing the body. Almost four years later, and the front tank that worked before no longer wants to cooperate with me.

I filled both tanks after the body work was finished and went on my way. I had left the switch on the rear tank through all of that time and did so until I flipped to the front tank a few days later and the truck went dead.

Sitting idling, driving, whichever... When the switch is flipped to the front tank, the motor dies.

To me, I say it's the fuel pump in the front tank. However, before I tear in and replace it, I want to make sure there are no other possibilities.

BTW, when the switch is flipped to the front tank, I can hear the pump come on with the key...

Thanks for any insight!

 

Possibly sludge build up in the lines. or you have air in the lines. try turning the key on and off a dozen or so times(just long anough each time to let the fuel pump do its job, useing the front tank), or just let it sit there for a while, with the key just turned on.

 

Put a fuel pressure gauge on it see what the value is front and rear tanks, there is a chance it might be suffering the fuel transfer issue. Fuel pumped from front to rear tank, might be to the point not enough pressure left over for engine to run. Haven't seen where anyone suffered it to that point yet but who knows maybe yours prove exception to the rule.

Equally possible the pump makes noise just doesn't move much or any fuel.

When testing fuel pressure you have to cycle the key on and off, computer will only run pump for a second or two after first turned to run position then stop each time.

You can also power pump from PCM test port, ground port marked fuel pump shown in the picture here with key in "run" position, selected tanks pump will run continuously.

http://www.oldfuelinjection.com/?p=13

Could leave it to run for several minutes, see if level of fuel in rear tank goes up. Should prove fairly easy method while at it see if suffering fuel transfer problem. If fuel pressure gauge shows little or no pressure from the front tank and the level in the rear tank does go up, replace the FMU in the rear tank.

 

are you getting a reading on the gas gauge of the amount of fuel in the front tank? If not then check the 4 pin connection going to the sending unit.

 

Thanks for your responses, everyone!

It's been around two years since I filled the front tank and tried to use it. Once I saw that it wasn't going to work after several attempts, I siphoned out all of the fuel and used it in the lawn tractor. The next time I buy some fuel, I'll put five gallons or so in the front tank and try all that's been suggested here.

Will advise shortly, and thanks again!