79 300 SD TURBO won't shut off with key
 

I have a problem with my 79 sd turbo it just started the other day I have to use the kill button in the engine compartment to turn off engine.I have had this problem before but it was the vacuum line that came undone. repluged amd it worked fine. This time it was unpluged re pluged and nothing. Any help would be appriciated.

You've definitely got an issue at hand involving vacuum. Could be a leak in the central lock system, a bad shut off solenoid on the IP or a bad vac switch at the ignition tumbler. Are you familiar with testing procedures? You'll need a hand vac pump to begin with...

I'd say you got a vacuum pull off issue . Check the back of the IP and see if there is oil in the vacuum line going to the sut off. You can also remove and manually see if it will hold its "pull off" posistion. Be very careful on RR of this device making sure you replace in same fashion as removal and making sure the pull off lever connects to the IP lever. If you do not , a runaway engine could result and that is not good

What has been done to the car recently. This is frequently the key to where the problem qriginated.

Are there any other vacuum related issues; late shifting, central locking, ACC?

With the engine running, turn key off, engine still runs? continue=>
Remove vacuum line to engine shutdown diaphragm.
Put finger over vacuum line. Does it suck against your finger?
- No, indicates that you have poor vacuum from shutdown vacuum switch on ignition switch. Pull the instrument panel to check the connections. Replace any perished hoses. Recheck.
- Yes, indicates you have an issue with the shutdown diaphragm.
Connect a piece of vacuum hose to the shutdown diaphragm and suck on it. Does the engine shut down?
- No, you have a problem with the shutdown diaphragm.
Do you have airflow from the shutdown diaphragm?
- yes , you have a problem with the shutdown diaphragm.

If you have access to a vacuum gauge of MityVac, measure the vacuum at the vacuum connectoion to the vacuum connection to the main vacuum line to the Brake vacuum reservoir.
You should have >20"Hg vacuum there with the engine idling and no leaks. Block off the connection to the brake vacuum reservoir if you cannot get >20"Hg vacuum.
If you still cannot get a good vacuum, it is most likely time to rebuild the vac pump.

I actually knocked a line off while playing around with radio instalation and the result was a "no turn off" engine