after pump replacement runs rough

[BIGTPM73]

I just had my injection pump replaced. on my 98 td 6.5L. I had intermittent problems with my old pump, until it finally went. before, when it was working between stalling, the truck ran well and smooth. It also would start easily when it was cold. Since I had the pump replaced, it takes a little more to start it, and when its cold, it hesitates and seems to miss when I accelerate. It will seem to bog down when I hit the accelerator, and then suddenly kick in and take off. Once it is warm, it runs better, but it still seems to miss a little when I am driving steady on the freeway. I don't notice the RPM's drop on the tachometer, but I can feel it, and I had my wife in the truck and she felt it too, just to be sure it wasn't my imagination.

My mechanic thinks it is something else, but I really think the pump timing is slightly off. The fact that it didn't do this when the old pump was working, but does it constantly now, gives me that suspicion. I also have a spare PMD, which has been relocated, so I changed the new one to the spare on, and noticed no real difference.

Does this sound like the probable problem??? Thank you

[joed]

Was this replaced under GM's extended 120k/11 years warranty by chance?

Reason I ask is I had similar issues on my 98 after a warranty IP was installed a few years ago - With colder outside temps, it would miss/hick up until it the coolant temp. was around operating temp. Once warm, it ran fine. I think the culprit was the actual fuel solenoid on the IP - not the FSD/PMD. Reading the fuel solenoid closure times on a scanner always showed over 2 ms - I think it should be around 1.9ms or less. I also tried a different FSD with the same results.

Since the only fix is to have the IP replaced or adjusted by a Stanadyne shop, I just lived with it. It always started cold great and ran fine once warm. If you're still under GM's extended warranty, you could try and get another IP that's hopefully set up better.

I'm not sure if this is unique to GM warranty pumps, but I've heard of a few with similar issues.

Joe.

[BIGTPM73]

No, its not under any warranty. It just past 210k miles. The guy who did it for me is a mechanic at a GM dealer. I bought the pump on web from a store reccomended by the diesel page. I may try to call them, to see if they have any suggestions. Thanks.

Tom