Some notes on rewiring an ignition switch on my 1980 300TD Euro, which is very similar to the 240D.
50 Purple/white to Connector C146 for starter safety switch 30 Red Always Hot, Pin 30 of headlight switch P Green/White P30 on headlight switch 15 Red/Black Fuse 12 15 Red/Black Fuse 12 30 Red Always Hot, Pin 30 of headlight switch P30 Red/Green to pin 30 of Ignition Switch (But not sure on this one) R (=Run) Red/Green to Fuse F4, Hot in Accy, Run, Start
The oil in the switch is an indication of a problem in the vacuum system at one time. There is a vacuum switch that routes or blocks vacuum to the shutoff control on the rear of the fuel injector. When the switch is in the off position, vacuum is routed to the shutoff. In the run or start position, vacuum is blocked.