Common problem. Vacuum line to shutoff device on the aft end of the injection pump can be knocked off while changing the filter, or the connector can just be old and cracked. If there is oil dripping from under the dash in the vicinity of the starting key tumbler/switch assembly it is likely the diaphragm in the shutdown device has ruptured. Changing the device is not difficult, but be careful and do a search to get some clear instructions. Failure to properly engage the linkage from the shutoff valve can result in losing control of the engine, which means it revs at no load when you start it until it dies unless you shut it down by cutting off fuel manually (pull the fuel line off the injection pump) and cover the air intake with a 2x6.

If the shutoff device diaphragm has ruptured you will also need to replace the rubber connections to the dash switch as they will get soft and gooey, and never stay put on the vacuum line or the nipple on the switch.

Good find. Just no rust and a correctly running engine is worth the price!

Jim

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Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)