Oil gets into the ignition switch from the vacuum switch that attaches to the side. That switches vacuum to the stop-valve on the rear of the injection pump. When the stop-valve's diaphragm tears, oil gets sucked up the vacuum tube to the switch, eventually dripping on your right foot (ugh). Install a tiny clear filter in that tube so you can monitor for oil before it gets everywhere, and know to change the stop-valve.

__________________
1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans