Charle ... 4/10/2010
1984 Mercedes Benz 300CD Base 5 Cyl 3.0L
Engine will not stop when I turn off the key.
This is caused by a leak in your vacuum system. Possibly in a door or trunk lock. It takes vacuum (suction) to turn off your fuel supply. You can turn it off manually by lifting the hood and holding the lever down that says engine turn off. Look for vacuum hoses that are disconnected. Your vacuum pump could also be weak, there is an inexpensive repair kit available.