Snibble:

A puff of blue smoke on startup is a definite sign you need new vavle guide seals, since oil will seep down the guides with the engine off when they get worn. You won't see the oil smoke with the engine running, just when you start up.

You will also get mixture control problems when the guides get worn -- air leaks in. Can get so bad you cannot get decent idle, although the car will run fine off idle.

You can check the mixture and lambda control with a digital VOM that reads duty cycle -- Sears has several models for about $35.

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!