OK, first off I am not involved, nor am I a mechanic, at least not a professional one (I could be called a shirtsleeve mechanic but I am more into electronics than working on diesels)
I have a friend that is a mechanic at least he gets paid for working in an Indy shop. He likes to look at my '87 300D and likes to visit when he sees me changing oil or something with the hood up.
He related a problem he has had with a Sprinter, an early body with the straight six engine in it, I was told it is the same as my OM603 but not sure if a turbo and not having seen it first hand I can't say that's what is really is.

But here's the problem:
The owner shuts off the engine which was running fine then the next time he cranks it it makes a noise and won't start. Towed to the shop, my friend finds the main nut at the front of the crank is dislodged, backed out. He retightens it and a few weeks later the same thing happens. He used locktite and torqued to spec but it happens a second time so he claims to have drilled and added a locking pin next to the hex and be darned if it broke that off the third time!
Now he won't work on it, or maybe the owner doesn't want to pay for all the failed effort? I don't know but I suggested maybe he has a timing problem and or a loose timing chain and when the engine is shut off it runs backward if its switched off at the right point. The way I showed him my engine stops dead in its tracks when I turn the key off, that is not what's happening on his customer's engine.
Anyone with experience have a idea what's going on?
DDH

__________________
'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!