lorenzg

I have a ’96 F150 with a in-line 6cyl motor. It was bought used and appears to have some ‘issues’. It has duel metal tanks. The problem is that the front tank appears to be being filled (over filled actually). When the system is over-pressurized, it begins to run rough intermittently. A couple of things that I’ve noticed: 1) I can hear the pump running in the rear tank when this happens, 2) when this happens and we turn off the motor, the vapor canister in the engine compartment is filled with fuel. The fuel appears to go away when the engine is running.
My thoughts are that the fuel delivery module in the rear tank is Tango Uniform and is pressurizing the front tank. I also figure that the easiest way to replace either pumps is to remove the pickup bed. Any thoughts or advice will be appreciated. Thanks, Rich

wde3477

Welcome to the site!

Couple of questions to help me understand the problem better -
1) Which tank is selected when this situation occurs? I am assuming since the rear pump is running, the rear tank is selected?
2) What do you mean by 'over-pressurized'? Is this just the front tank over-filling, or have fuel pressure checks been made?

Offhand, I would suspect the switching valve for the fuel tanks - not only does it have to choose which tank the fuel is coming from, it also has to send the returned fuel back to the correct tank. Not sure why this would cause issues with the engine, unless the fuel rail pressure regulator operation is being interfered with due to this switching valve, or perhaps raw liquid fuel is being sucked in through the vapor canister, where the motor is typically expecting gasoline vapors.

Not much personal experience with dual tanks here - just tossing out my two cents' worth.

Good luck, and keep us posted on what you find.

nemos

Hello,

I have a friends truck that is having ther very same issue, please let us know what you find to fix all this.

Kevin

homeskillit37

Sounds like the valve that switches between tanks. We had a problem where it just kept putting fuel from one tank into the other where it would spill out. We had to replace that valve that switched the tanks. Its a dealer only item. you can buy them at parts stores but the don't work properly. the local parts store told us they could sell it to us but we would end up returning it and just go to the dealer.

lorenzg

Well, yesterday was the big day. We pulled the bed off the PU and replaced the internal pump assembly. The toughest part of the job was to get the two bolts closest to the cab out. One was rusted enough that it rounded out in the bed and just turned. We used a die-grinder to cut a slot in the head of the bolt to accommodate a big-***** screwdriver I have and we were able to get the nut off. I was only about one more try away from tack-welding the bolt to the bed and then removing the nut, but with the help of some BG NForce it went OK.
This was for a friend and I heard last night that the truck stalled on him on the way home, so the problem may not be fixed. The whole job from start to end only took 4 hours, so the next time it should be quicker. I can’t imagine trying to replace the in-tank pumps w/o pulling the bed. Dropping the fuel tanks seems like a royal pain. I can see that it would be pretty easy to break a fuel line.
More to follow.