The '83 300D did not have a vacuum pump in the trunk. I'm not sure what you have there that runs all of the time.

You can buy a CD-ROM version of the factory service manual (FSM) from Mercedes for about $20. See this link click on "Classic Center" and select "Technical Literature." The part number is QL-6550-1460-02.

Jeremy

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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970