Hi, I have an 85 300CDT that runs a bit rough at all power settings. I have done the following: changed all fuel filters including tank strainer, swapped injectors and heat shields from a good running car, did a diesel purge, adjusted the valves, checked engine timing, did a compression check (well over 300 psi on all cylinders), changed primer pump (was leaking), swapped EGRs from a known good engine, adjusted ALDA, changed rack bolt, removed the intake components to look for obstruction, removed the exhaust just after the turbo and ran the engine, turbo spins up nicely nothing has changed. I took the car out for a good high speed run (75-80 MPH) for about 50 minutes. The car is louder than it should be and seems to lack power compared to my 300TDT. Beginning at about 1000 RPM, it has a "chug-chug" sound and is almost like a miss. If it was a gasoline engine, I would have to say it was retarded timing. #1 injector looks normal after running the engine, but #2-5 get a black covering on the entire bottom face of the injector, not just the middle around the nozzle. It may be a problem with the pre chamber.

I don't want to start changing out expensive parts only to find out it doesn't change anything. I'm thinking injection pump?

Anyone have any good suggestions? My local Mercedes "expert" hasn't any better ideas.

Thanks,
Bob