Mercedes Benz repair: 1983 300td, vacuum line, vacuum tube

Question
car runs great, but won't shut off even after key is removed. Must open the hood and manually stop. is this the vacuom off of the ingnition switch?

Answer
Yes, that vacuum line feeds the BROWN vacuum tube connected to the vacuum shutdown valve at the rear of your injection pump.
If the line is dislodged or broken the engine will not turn off.
This is the most common issue.
Did you have an oil change or other work, roughly the same time the issue started?
The following link is to a picture that may help you.

http://www.mercedesshop.com/shopforum/attachment.php?attachmentid=21209&d=109598...

Please feel free to followup with further questions if this does not fix the issue.
Have a great day.
whunter