Mercedes Benz repair: Car continues to run when ignition turned off., vacuum pump, vacuum system

Question
I have a 1984 Mercedes 300sd turbo diesel that continues to run when the ignition is switched off.  How do I check to see if it is the ignition switch are something else?

Answer
These threads should answer your question.

Run away diesel, why does it happen?
http://www.mercedesshop.com/shopforum/showthread.php?p=824840#post824840

wont start for anything!
http://www.mercedesshop.com/shopforum/showthread.php?t=104222&pp=20

190D Won't turn off and no Stop Lever!
http://www.mercedesshop.com/shopforum/showthread.php?t=88023&page=3&pp=15

Rebuilding the Vacuum Pump on the 617 Engine
http://diymbrepair.com/easley/Rebuild_vac_pump.htm

1982-240D-Vacuum System
http://www.mercedesshop.com/shopforum/showthread.php?t=105201

Vacuum pump lesson learned
http://www.mercedesshop.com/shopforum/showthread.php?p=872760#post872760

Vacuum Pump Gasket Sealer & Torque
http://www.mercedesshop.com/shopforum/showthread.php?t=138153