Car: Mercedes Benz 1991 300D 2.5 Turbo

I posted about this problem before but now I have a lot more information. This a bit long but I want to give as much info as possible to diagnose the problem.

I had a bad leak on 2 of my delivery valves on my injection pump. I Just replaced all 5 of the seals, copper and o-rings and put it all back together.
Torqued to spec 2*30NM last one 35NM. After about 45 seconds of cranking all the air was purged out of the system and the engine started. Well, the leak is fixed but I noticed right away a loud metallic nailing/knocking noise some shaking and smoke from exhaust in idle. Driving the car, I do not notice any difference from before the "fix". The clicking disappears above 1200rpm. Good acceleration and no hesitation or other problems as far as I can tell. As soon as the rpms drop below 1200 nailing and smoke comes back. When the engine is warm the idle is nice and smooth but still with all the knocking/nailing.

I thought I made a mistake and repeated the procedure with new o-rings and copper washers but get the same result.

When I opened the delivery valves the first time, a lot of diesel came out and the little cavities where the delivery valve screws in was filled with
diesel. When I did the job the second time, there was no diesel running out at all and the cavities were empty. Looks like the diesel drained back into the pump. When I took out the first delivery valve I also heard a sucking noise as if there were a vacuum in the pump that sucked in air.

Other Symptoms that were not there before the "fix": When I shut down the motor I can not start the engine unless I push the stop lever on the injection pump back up. Seems like the stop lever has some problems in the down position. It seems to get stuck all the way down. I disconnected the vacuum line from the shut off valve and it is still stuck down. I can push it up and then pump a vacuum with a mighty vac and it goes down and gets stuck again. Also noticed on one occasion that it did not shut off with the key since the lever got stuck shortly before the shut off position. I had to push it down by hand to shut it off. Shut off valve problem? Related to problem above?

When the car sits overnight it starts up immediately and idles great, as it did before, without knocking/nailing for about 30 to 40 seconds. I guess that is when the glow plugs shut off. After that it is a terrible idle, sputtering, smoking and shaking. Once I drive it calms down quickly but the loud knocking/nailing below 1200 rmp is persistent.

Oh , I did also replace worn out fuel injector fuel return lines when I did the first job. I don't see that this has anything to do with the problem but I mention it to cover it all.

Can I drive the car until it is fixed or will I permanent damage anything?

What could have possibly gone wrong? I did this job before without problems on an older diesel??

I would take it to an Indi bu I can't find anybody in my neighborhood and the closest Mercedes dealer is 50 miles away and I want to avoid a dealer anyway.

Thank for looking
..Udo

Changed IP O-Rings, now have clacking...

Sounds similar to my problem, only I can hear the nailing all the time.

Cant answer the Q, but my car does the same thing, has since I got it, and I'm damn curious to find the cure. As you'll find, diagnosing a compression engine is MUCh harder, imho, than a spark engine. But dont give up.

Wonder if anythign foreign got into the lines and is buggering up an injector. It doestn take much.

I wonder if you have a tired injector or two - that would give you the nailing. It doesn't explaine the stop lever issue however, and that points to the IP...hmmm.

I assume that you have gone through the usual and have clean fuel filters and fresh fuel?

Fred

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'92 300D - 140K - Just a Puppy
'91 M5 - Garage Queen
'90 V8Q
'99 Dodge Ram Cummins 24V
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