Dont get discouraged ,get it home and let us talk you through it.Dosent sound too bad. Hang in there..

 

I would go out and start it again.

That sounds like just about enough time for the tank vacuum to let it get fuel again.

When the engine starts stumbling, remove the fuel tank cap.

If you hear a sucking sound and the engine straightens out right after that, the tank vents are blocked with mud.

 

Sounds possible. I just wondered if maybe his fss wireing was working loose when it warmed up. I had a car that no one could figure out. It kept quiting after it warmed up. Turned out to be a wire sagging with the heat and looseing contact. Wait a little bit and it would cool enough to make contact again.

 

It's not a wiring issue, it's a fuel supply issue or Injection Pump issue.

As soon as it dies, test the fuel flow at the schrader valve on the filter head.

I suspect you have a suction side air leak, how is the hose from the hard line on the frame to lift pump??

Or as Dave S. suspects ... Plugged vents.

-Enjoy
fh : )_~

 

I wonder why he changed the lift pump. Does any body remeber if he posted that?

 

He didn't say why the lift pump was changed ... I suspect for this problem.

6.9lXLTf250, You pulled the tank, did you replace the pickup tube in the tank ???

How much fuel is in the tank ???

-Enjoy
fh : )_~

 

The how much fuel is in the tank could be the answer, correct question here.

What did you extend the suction line with when you removed the broken rubber line extension?

If nothing, then the truck will run out of fuel somewhere between 1/4 and 1/2 tank of fuel.

So if you have less than 10 gallons in the tank, it is just running out of fuel.

Use a section of 3/8" fuel line to extend the suction line to the bottom of the tank.
When you put the line on, cut a V in the end of the fuel line so it can not suck up against the side or bottom of the tank shutting off the fuel flow while driving.

 

hey sorry i have been busy with work.

the lift pump was replaced due to it leaking.

even if i run the truck with the gas cap off it still stumbles and dies.


after it dies no pressure in the shreder valve. almost seems like pressureised air comes out.

 

truck has a full tank of fule

 

You have an air leak on the suction side of the lift pump ...

That means from the lift pump to the bottom of the tank!

Pickup tube in the tank.
Connections on top of tank.
FSV connections.
Rubber hose Frame to Lift pump.
Any of the solid lines in between.

-Enjoy
fh : )_~

 

hey the pick up tube is a section of 3/8 fule tubing.

the line from the frame to the lift pump was replaced on saturday.

also replaced the fuel water seperater bypass.

The fsv is busted so it is compleatly bypassed.

so you think it could be the breather for the tank?

 

after reading this entire thread,im going to say your ip is shot.
this is called heat soak.
it all adds up.everything is new,and the fuel is constant at the filter.
(started with info in the first post - "the lines are good and not rusted, and i am getting fule from the lift pump to the filtefrom the fule filter whitch is also new im gettin about a 1/3 o a pint in 10 seconds.")

the mileage is unknown,and its an old truck.
pretty good bet you could use a new ip.

in your first post,you mention it starts and runs fine until it warms up.
generally if this were air intrusion,or a bad tank(pickup/vent etc) it would seem,to start hard,or at least stall out right after it was started(once the fuel already in the ip burned out,so like 30 seconds maybe?)

if it runs long after the fuel from the ip to the injectors has burned out(just a min or so at best?) and there's fuel always at the filter,yet runs long enough for engine to actually warm up.....well,sounds like a bad ip.

so you can start the engine,and it will run fine until it warms up.about how many minutes does it take from start up to stall?
like 5-10 minutes?

you could give this try first,it sure couldn't hurt:
https://www.ford-trucks.com/forums/9...r-revving.html

to check for heat soak,try this:
check this whole thread:
https://www.ford-trucks.com/forums/9...-much-hot.html

edit:
"after it dies no pressure in the shreder valve. almost seems like pressureised air comes out. "

i missed that.ok,that sucks.
man,i don't understand why you guys stick with them old lift pumps.
i would have been stranded at least twice by now.
what are the odds of him having a bad lift pump out of the box?


6.9lXLTf250,
unhook your line from the lift pump,that goes to the tank.hook a short hose to this port on the pump,and put it in a gallon (or more-just make sure it stays submersed and doesn't suck to the bottom) jug of clean diesel.start the truck(fill your fuel filter first to help ease of starting) and see if the truck runs steady past warm up then.
that will tell us a lot.
see what your doing? your bypassing the trucks fuel supply line and tank(normally eliminating the fsv too of course,but in your case its already bypassed) and just checking to see if it will run directly from the jug.

there's only so many possibilities with such a basic simplistic setup of the IDI.it's just a matter of process of elimination to find the problem.
thats why i get a chuckle when someone says they like the simplicity of the IDI,and dont want to complicate it with an electric fuel pump.bypassing the old mechanical for an e-pump is already a much more simple concept lol.you turn the key,your pumping fuel.nothing is more basic or simple than that.

6.9lXLTf250,
one more question.when you bypassed your FSV,you made sure you connected the proper lines back together and didn't get them crossed correct? supply & return you made sure are both connected?

 

Did you cut a V notch in the end of the 3/8 hose in the tank? Make sure all te clamps are tight on the replaaced lines.

 

yea, the truk starts hard like it loses its prime.

i let the truck idle for thirty mins, after that i ran the hell out of the truck. it ran fine, all i did was retighten every thing and it ran fine. even at freeway speeds.

 

yea i think an electronic pump is on the hit list now.