Allright, here it goes. Just bought 96 GMC 2500 4x4 with 177,000 miles about a month ago. Love the truck, but darn stumble, and same codes set. Already has SSdiesel relocator, 3" exhaust straight through turbo to tip. Had a leaky crossover tube, so i removed the intake. While there, replaced hoses, fuel, and water. I replaced the oil pressure switch. I also put on a lift pump. I replaced the fuel filter, and tested fuel pressure. Pressure was good at about 6 psi at idle, 2-3 psi when throttled up. Test was done at t-handle.

Now here is the thing, intermittent stumble. when it is happening, oil pressure is good, water temp is good, and voltage is good. No noticable smoke. Usually no codes. When codes are set, P0251, and P0370. I have removed the optical sensor filter as soon as i read about it.

Engine cranks, and starts, but when cold or warm seems to take 5-6 revolutions before it will fire. When running, runs great untill check engine lits up. Yesterday, it actually didn't want to start warm until i gave a little throttle.

I love my truck, converted to diesel from a gasser, just have a few bugs to work out. Hope you all have some good places to start. Thank you for any help!

you should list your truck in your signature,makes it easier to determine problems.
go to the FAQ's and fill out the checklist.
i have tested my truck fuel pressure - i have a good quality fluid filled gauge, connect a 1/4" or 5/16" line about 7' long to the t handle, run the fuel line out thru the hood along the drivers side (it's tight, but i have found a spot near the hinge it doesn't crimp). i use tape to hold it to the outside mirror so i can read. open t handle a few turns. heath diesel says DO NOT put a fuel gauge in the truck, if anything breaks, you will NEVER get rid of the diesel smell.
with the old standard LP ( w ill be installing a new HP LP soon) at idle i get about 7psi, at WOT laying on the power, accelerating, highway speed, the most fuel it could use, it is a minimum of 4.5psi. absolute minimum is 2psi it will run, less and it over works the IP.
your psi is minimal.
you might want to check the fuel tank sock to be sure it isn't clogged, then work your way forward.
beyond that, what do those codes mean?
http://www.dieselplace.com/forum/showthread.php?t=100323
check this thread
jon

Get that PMD moved the SSDiesel relocator (on the intake) is just as bad as having it still on the pump, the best place for it is out front where it gets lots of cold air to keep cool. Not sure if that is what is causing your stalling, but it will save you future headaches.

The pmd really is a piece of. I mounted mine out front of the truck and the stumbling and hard starts have gone. Inside the engine compartment that thing gets hotter than hell and will fail. Never knew when the engine would stop and have to wait for 10 min plus to start again.

Thanks for the info fellas, and thank you jb, for the link! If you have any more ideas, let me know!

When was this converted to diesel? Do you know if you have a 96 diesel engine and computer?

My PMD has never gone over 150*F on the intake, and the IP is usually 20*F hotter without any PMD on it. So its not just as bad on the intake, just not as good as out of the engine bay. And if you trust D-Tech's rating to 257*F (125*C) then in the engine bay should be OK, but still off the pump. The Stanadyne PMD, no way leaving that in the engine bay. So if you have a Stanadyne might be the issue, SSDS stopped selling them over a year ago, if it were Stanadyne it would say it on it.

i'm sorry, I converted to diesel, not truck, LOL. Sorry for any confusion. Thanks 94C another great point. I'll be moving PMD.