So I've had this odd event a few times when starting my 115. When I pull out the starter knob (after letting the gps heat up) I get that grrrr sound as if the engine has already been started. Any ideas what my cause this?

__________________
1987 300TD; 166,000 mi/267151 Km - had to make room for the dog
1973 220D; mileage ??????
1978 300D; 178,000