My 77 240D has the vaccuum pump with an inlet and outlet. The 83 SD just has the one hose.

When the diapgragm ruptured on th 240D oil was pumped to and into the air filter housing, along with the ignition switch and brake booster. That how oil could get into the pre combustion chambers. I don't see how that much oil could be pushed as the pump is splash instead of pressure lubricated.

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Fred Johnson
1977 240D
1983 300SD