Sounds like a vacuum problem. To shut off these cars the fuel flow must be stopped. First check the vacuum line connections on the ignition switch by removing the cover under the dash on the drivers side. Also check the vacuum line connections on the Injection pump. There are lost of good threads on this board about this problem. Good luck.

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine