Just finished a successful IP replacement of a 97 6.5TD. I checked every checklist and diagnostic routine on DB and other 6.5 sites, and came to the conclusion that I needed a new IP. The following GM checklist was the most useful that I found in that it very quickly indicates where the problem lies.



When reinstalling, once the new IP is slid into place, and the top nut fitted very loosely (enough to keep the unit from falling off), re-install the two lower injector lines. You can wedge the back of the IP unit slightly upwards with pry bars or similar to make it easier to access those lower lines.

If you haven't already relocated the PMD, now is a good time. Not having the PMD on the IP makes it easier to get the drivers-side securing nut on and tightened. A 12 point 15mm deep box ring will become your friend when removing and tightening those two lower nuts. Long, slim fingers helps too. Arm wrestlers will never refit those nuts!

I read about cracking open the injector lines to bleed the system, but went for the easier option of removing all the DS glow plugs since they are all easy to get to. The IP is self bleeding (well, for small air leaks, if the Teledyne info is to be believed).

One the GPs were removed, and after checking that I had a good flow at the T handle drain, it took about 30 seconds before the engine coughed and tried to start: I stopped immediately (it did turn over a lot faster with 4 glow plugs out). I fitted new glow plugs and tried again, the engine caught on 2 or 3 cylinders within 10-15 seconds, and then slowly, one by one, all 8 were firing cleanly over the next 30-60 seconds. Running like a dream now!

I hope I never do this job again!