Fuel system cut off solenoid???????

1985 300 D turbo (my car) has stopped turning off from the key. Must use under hood cut off switch. purchased haynes manual but this refers to the solenoid only once and this is in the troubleshooting section. any help,info appreciated.
thanks

[MikeTangas]

Sounds like a vacuum leak, more than likely. Have you changed oil lately??

I ask because it seems a common occurance to knock off one of the vacuum lines while changing/replacing the oil filter. Might also be rooted in the vacuum locking system.

Try doing a search on, something like "diesel wont shut off", you'll be surprised at the amount of reading you'll have.