what's happening to them? Are they just totally quiting on you? I'm having problems with my ecm frying. Just bought the truck in june and the 2nd one is going bad already. Makes me wish i stayed with gas. what year do you have?
I had a friend who had some trouble with his 94 K2500 6.5 diesel. He thought it was the injection pump, but it turned out to be the driver unit. Might be the driver, take it to a garage and have them see what the codes read on their scan tool.
The most common problem is the PMD mounted on the injector pump. If your truck will be going along just fine and shut off like someone turned the key off, the PMD is the most likely suspect. They are less than 100.00 to relocate a new one from off the IP. However since GM has extended that warranty, I let them eat that cost. I have had one go at 48K but none since. The dealers are useless, I had to expalin what was wrong, and how the X warranty worked, before I could get my truck back from them.
Since GM will pay for the whole pump to be replaced the dealers just un bolt the old and install the new one.
The GM diesel page has all the tech info.
My truck is a '97 Had a freind come down with a scan tool and i got all the codes off of the truck.Just got it back from the dealer and yes I made sure that i gave then the paper from GM with the 11 year warranty.They put the whole thing back together and found that it still rand like bad so they took the top off again and had to replace a colappsed fuel line from the filter to the pump.I'm really getting fed up with this truck gonna go thrue the winter with it then get into a Ford I think,not gonna deal with having to rush to put a plow and sander on the new truck right now.I was talking with a guy just the other day and he has a '98 K35 dump with the 6.5 and he is selling it because he's having problems with his but he beats the sh*t out of it. I have had nothing but one problem after the other.
Sorry to hear about your problems. When you finally get a "good" (newer) pump, they are usually OK for a long while. The Fuel Solenoid Driver that Dino was talking about does have a tendency to "go" but when relocated on a COOLER (FSD Cooler) insead of the hottest part of the engine, they last a good long time.
If you got it back after the pump swap and it runs crappy, ask them what they set the pump timing at. There is quite a varience here and lots of power can be gained or lost with the stroke of the Tech II.
These engines, while not nearly as powerfull as a PS or Cummins can be made to run real well and reliably in the 250 hp range. Its when your sneaking around the 300hp range that the bottom ends like to "exit stage left"