stalls on cold start...what gives ?

[Northern Wrangler 6.2]

New problem....first time the old girl has even hiccupped in 50,000 miles...

In the morning or after sitting all day (at work)...I start her up...lights up right away, as always, but then feels like it runs out of fuel....pedal non-responsive, engine surges, then dies......restart..(lots of cranking)....and it lights up again..then seems fine. When engine is warm, no issue, runs and pulls as always, fuel mileage good, oil consumption is unchanges, everything sounds the same.....started a couple hundred miles after fuel filter chenge. I added some conditioner to the fuel, drained the water from the seperator (none present)....

Am I sucking air from someplace ?.....lift pump weak, injector pump weak ?....am I losing prime after sitting ?....

Any help will be greatly appreciated.....long trip with camper and trailer full of junk for the swap meet next weekend.....don't want (embarrassed) to take my gasser....HELP !!!

[5.7L diesel]

Might be an air leak or a rotton fuel line hose allowing fuel to drain out that way.Or like you said perhaps a weak lift pump.I know that on some older 6.2's a bad check valve in the lift pump allowed fuel to run backwards after a period of time.

[BobND]

One common leak that lets air in and causes stalling is the plugged filter sensor on the fuel filter base, behind the fuel filter. Is the filter base damp, or does it have dust clinging to fuel that has seeped out?

A new "O" ring may fix this, or many of us have done away with the sensor, and tapped and plugged the hole behind it. Remove filter base to do that, and clean it up THOROUGHLY of filings.

Also, the mech fuel pump, injector pump throttle shaft seals leaking, or even injector return line leaks can let air into the system.

[john8662]

As Bob mentioned, even fuel return can cause this...

The factory spring type clamps used on a great deal of the return side of the fuel system don't hold after the rubber starts to harden a little. Replace the clams on the IP with hose clamps with the screw.

Check out the brief tutorial on finding leaks at the top of the forum, might help find the air leak, if there is one.

[ZZ]

I hate to say it, but it sounds like you are having the fuel leak down problem after she sits for awhile. Does it start and run a few seconds and then die, and then do you have to crank & crank to get the prime back?

My truck has done this twice in the last three years. A new fuel filter fixed it the first time. The 2nd time was a loose hose clamp on the pet cock valve by the thermostat housing.

[Northern Wrangler 6.2]

Well, I got lookin' nad saw that there was raw fuel dripping from my drain hose on the filter, so I took my fuel filter off ( I had used an old stock Purolator one), and installed a new Fram, (i believe it's the same filter anyways....but fresh)...took the water drain vavle out of the filter holder, cleaned it, put it back in, tight, no new o-ring (didn't have one handy)....ran it, everything is good. Waited to try in the morning, which was the true test, it is working great, no more loss of prime, seems to idle better ?...maybe was sucking air all the time....don't know, don't care, ready for trip tomorrow....

THANKS GUYS !!!!!!!!!!!!!

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