Pull the valve cover -- if the camshaft doesn't move when you turn the crank, the chain is broken. Should be obvious anyway, as it usually isn't on the sprokets if broken.

Can you spin the dizzy with the engine off? If so, more likely a broken dizzy than a broken chain.

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!