Hold the STOP lever down hard for a few seconds. That should kill it. Normal engine shutoff is done by a vacuum solenoid on the back of the injection pump. If it's not working, you have a vacuum leak somewhere. Look for disconnected hoses in the area around the oil filter and injection pump. It's possible the shutoff solenoid itsef is bad, but most likely just a loose hose.
2004 C240 Wagon 203.261 Baby Benz
2008 ML320 CDI Highway Cruiser
2006 Toyota Prius, Saving the Planet @ 48 mpg
2000 F-150, Destroying the Planet @ 20 mpg
And remember folks, Only You Can Prevent Hilliary.