b.lee

I checked the filter and prefilter. Both are fine, no water or dirt.

While in park, it will start up fine, idle fine, then out of the blue it will spit and spudder. It will stall but most of the time you can floor it to keep it just bearly running. Then it will smooth out and come back to idling and revving up smoothly. A few seconds later its back to running extremely rough and wanting to stall.

The truck has new oem fuel lines from tank to lift pump.
418k miles, I believe the original lift pump. Ran great for the past 55k miles

Any ideas?
96 12v 2500 4x4 in sig

b.lee

I'm thinking it could be the overflow valve. After letting it set for a few minutes the problem is cleared up for the first few minutes of running. After a 1-2 minutes, the truck starts running poorly and stalling. White smoke and backfiring. The only way to keep it running is floor it, even then it will bearly run 200-300rpms

patdaly

You need to get fuel pressure readings to verify.

b.lee

Now that I go out and look at the truck this morning... there is a big puddle of fuel in the snow, under the drivers side door.

This truck had new lines from the tank to the lift pump a few years ago, maybe there is some other common line or area that will rot away and leak?

infidel

If the lines were replaced with the stock steel ones they are likely leaking again.
Every inch of the stock fuel supply and return system is prone to leaks.
Replace the lines with quality diesel rated hose from engine to tank.
Marine rated hose will easily last the life of the truck.

b.lee

Thanks for the info.
They were replaced with oem fuel lines ....

I should have done the marine rated hose the first time... much cheaper.