Ah, ok. The OM603 I just installed in a 300SDL has a terrible leak at 4 of 6 of the delivery valves. It actually leaks back down, because as you crank to start it the next day, bubbles form where it purging air.

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1987 300SDL #1, 1987 300SDL #2, 1980 240D, 1982 300SD, 1994 S350, 1990 350SDL, 1991 350SD, 1985 300D, 2005 E320CDI

Gone, but not forgotten: 1981 300SD, 1982 300SD, 1987 300SDL, 1983 300TD, 1980 300CD, 1981 300SD #2, 1987 300D, 1987 300TDT, 1980 300D