Run then stall?

[Tojobro2001]

Hey all, I'm new to the forums and I've been checking it beginning of the year before they sent me over seas.
My truck will run and then stall at idle or when I let off the gas. I got a new PMD and lift pump, but still no luck. I new to the diesel community, and I want to start learning, but I a little stump.
Someone said I could be a relay. I got no code from the diagnostics.
Any help would be great.

[grancito]

Has the truck been sitting for some time? If so put some fuel additive in to free up the pump.

[Tojobro2001]

Yea the truck sat for 4 months, but the problem started before then. the old fuel pump wasn't clogged or anything. The fuel filter is new and still looks fine.

[grancito]

First try some additive, I put half a cup in the fuel filter to give it a high dose, works in a few minutes, Bardahl diesel additive is good, cheap first thing to do.