Leading cause of a suddenly dead engine on a car that age is a leaking suction line filling the IP with air. Can also be a leaking primer pump -- I'd replace it on principle it if is the old unscrew and pump type, they leak all the time anyway. New style is completely enclosed spring loaded type, never leaks.

Plugged filters would be a good suspect, too.

I'd adjust the valves and leave them a bit loose, chances are they are crudded up and will go tight again promptly unless the PO was good at keeping them adjusted.

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!