1996 Ford F-150 Duel tanks

Tiny
DJB1965
  • MEMBER
  • 1996 FORD F-150
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 80,334 MILES
Truck only runs on rear tank. The front tank is full with new gas but the truck barely runs when on front tank. Switch seems to be fine. I hear a humming/whinning when I switch to front tank.

Is it the fuel pump, flter? Is the pump in the tank or inline?

David
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Wednesday, January 2nd, 2008 AT 7:19 PM

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Tiny
INDYUKE
  • MEMBER
Does the pump in the front tank sound any louder than the pump in the rear tank? The pump in the front tank may not be putting out enough pressure/volume, or it could have bad check valve. There's a pressure test port on the fuel rail that you can use to check the fuel pressure with. The pressure should be about 42psi.
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Wednesday, January 2nd, 2008 AT 7:37 PM
Tiny
DJB1965
  • MEMBER
Yes the pump noise in the front tank is very noticeable while I cant even hear the rear.

When I switch to the front tank gauge reads full. The more gas I give it the worse it runs. So been running off rear tank.

It seems I am getting real bad gas mileage, just dont know how the system works. Never had a dual tank before. Is there a diagram I can find online showing how it works.

Is there seperate fuel pumps, filters?
Are they in the tank or online?

Thank you vey much for your quick response

David
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Wednesday, January 2nd, 2008 AT 7:51 PM
Tiny
INDYUKE
  • MEMBER
Yes, each tank has it's own high pressure pump. In the tank itself. When you select a certain tank, that pump turns on, the other one turns off and fuel is pumped to the fuel rail atop the engine. The pump always pumps more fuel than the engine could possibly ever use, so there is a return line via a fuel pressure regulator. Each tank has it's own return.

I don't think you have a bad fuel pressure regulator, because the truck would run equally poor with either tank selected. A noisy pump is often an indication that it's going bad, though i've seen noisy pumps last years so long as the tank isn't run dry of gas. The gas in the tank cools and lubricates the pumps, run out of gas several times and the pump could burn up.

The first thing to do is check the fuel pressure at the fuel rail, while the truck is running on each pump. If you find that you have low fuel pressure while running off the front pump, then I would suspect either a bad pump, a bad check valve (which is in the pump) or an obstruction in the fuel circuit for that tank. A plugged filter would do that, however I haven't seen but one fuel filter that services both tanks in these trucks. I'd check it, or replace it if you haven't done so in a couple of years.

I know there's a way to post pics on here, but i've never been able to figure out how.
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Thursday, January 3rd, 2008 AT 8:28 PM

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