You need to reset the timing -- someone has set it with a stretched chain.

Also, you may have had very late timing with that much chain stretch, and only now are hearing "normal" diesel noise. MB engines are definitely diesels, and sound like them. Usually don't hear much knock at speed, though.

Also, make sure you tensioner is working -- chain slap can sound like injector knock, too!

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!