cptarmy2002

Ok - Long story short...just came back from 1 year in Afghanistan and purchased a 88 F150 XLT with 141K miles and 300 6 cyl with Fuel Injection. Goal was to do yard work and carry my dirt bike out to the track every couple weeks so I don't really need anything new.

Truck runs strong and when I brought it home I had 1/4 of a tank in the front and almost empty in the rear.

Filled both tanks up and they are leaking like a siv when it runs and then it slowly stops to no leak when the truck is off (about 2 minutes and the leaking stops). Switching from front to rear tank doesn't seem to have any effect.

The only other variable was 1/2 a can of seafoam in each tank when I gassed it up.

I can't see any obvious leaks in the tanks, so I'm thinking the fuel lines when they are under pressure?

Any thoughts would be appreciated.

Frank

bradseabridge

your system has a pressure leak somewhere, turn the truck on and look for the drips.

ymeski56

Leaking from "where" more specifically? You might have to get under there to narrow it down. Sounds like from the fuel delivery system than the tanks, except this didn't occur when the one tank was only 1/4 &. the other almost empty. you have vent lines on both tanks that might get into the act w/ full tank conditions...

bradseabridge

that.

ymeski56

By the way Frank, "Thank you for your service".



This is your tank diverter valve. it is mechanically switched via pressure provided by the individual low pressure in-tank pumps. Check that puppy out good. (your year truck also has a high pressure pump, the low pressure pumps feed/ this ones located on the frame rail in the vicinity of the in-line fuel filter & tank diverter valve).

cptarmy2002

Thanks for all the replies...I've got the Haynes manual but it's pretty much useless outside of engine stuff.

The leak seams to be coming from somewhere on top of the driver side mounted tank and then drips around the tank to pool on the ground. It is at both the front and rear of the tank, so it's two places...

Again, with this stupid useless manual, I can't even figure out if I have to drop the tanks to get at the valve to check that as well.

Any tips on getting at that valve and or how to check to vent lines?

Thanks again...

ymeski56

The high pressure pump, inline filter & tank diverter valve hang off the side of the driver side frame rail. It sounds like your problem(s) lie on top of the tank. Either vent or fuel return line(s).

W/ full tanks, best option is unbolting the bed & lifting off the bed. Sounds worse than it is. Not as heavy as you'd think. If one of these lines have failed, the other are also suspect. This is not that uncommon in vehicles over 20 yrs old.

If either tanks don't read correctly on the gauge, a good time to replace the sender unit in that tank too.

cptarmy2002

ok...well unfortunately this sounds like a problem I'm going to have to throw money at...although I'm a pretty fair mechanic, I'm at the Pentagon now, so I have absolutely zero free time between the horrific 1 hour plus commute each way and the 12-14 hour days...I only paid $1500 for the truck so I've already got it in my mind that I'm probably in for another $1,000 for this to be fixed...everything else works great on the truck, so if that's all that is wrong with it, then I guess I'm lucky...

ymeski56

Condolences. To bad. It's mostly labor intensive & sounds like a bigger deal than it is. If a prospective repair shop talks like it is, w/ a big ticket estimate, consult another shop.

Now the good news. We're talking rubber hoses that are unfortunately, hard to access. that's all! I love my 87'. Once you take care of the few thing's you might expect from a truck that old, Is should be reliable to the point of almost boredom. Stay on top of the condition of the oil & tranny fluid, flush radiator contents & run an antifreeze/ DISTILLED WATER ONLY mix, a bottle of Lucas injector cleaner every 5 tanks of gas & drive that puppy!

I do highly recommend switching to synthetic oil & tranny fluid. And to insure peak performance/ MPG, get yourself an OBD1 ECU error code reader. Plug & play, w/ digital numeric display & memory. $22.77 (cable is optional, not required) But the make & model shown is the one you want. All others at that price requires decoding flashing light #'s . Available in stores, still less than $30. If you think a senor is pooched, it will tell you & tell you which one.
See link:http://www.handsontools.com/Equus-In...ol_p_5574.html

cptarmy2002

Ok - It was dry enough for me to go out there for a few minutes and poke around...Thanks again for everybody's advice.

It is absolutely not leaking from the switch, It's leaking from somewhere above (or out of) the top of the siderail fuel tank and then dripping 180 degrees around the tank to stream onto the ground...

I found the switch on Amazon for $160, This is the one that looks exactly like mine.

From what everyone says, this is the problem and a super easy fix because it's accessable. But if it's not this switch, I'd hate to spend the $160 for nothing...might as well dump it off at the dealer and say "fix it."