I have a 3 second dieseling after turning the key on my 95 E300D. I took the posted advice and changed the vacuum diaphragm on the shut off valve, the two short rubber hoses that come from the key switch and checked the hoses from key to valve. I've run the problem back upstream and it must be the key switch itself. Any experience out there with the switch itself? Can it be cleaned/repaired or just changed out?