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?

I don't think you can repair it, just swap it out.

Does it leak off vac?

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

After changing out the shut off valve diaphragm and inspecting the ignition it turned out to be the primary vacuum line to the switch was partially plugged with gunk. It would hold vacuum etc but the decreased volume slowed the shut down process. That took awhile to figure out. Broke the threaded portion of a screw off and threaded the old line to the new and pulled thru the harness very smoothly.