We have a 79 300sd and when you go to turn engine off the motor wants to stay running, after you reve the motor up and turn the key it will cut off. Help us please.
Run some valve cleaner in your gas, on old cars I've read that you should do this often. Seems if there are deposits in your valves they stay hot and ignite any left over fuel.
Also you may be running rich, or have a fuel injector stuck open.
I'm no expert on these (or any for that matter). I believe your system shuts the fuel off when you turn off the key. It does that through a vacuum actuated control. Chances are, a vacuum line has started leaking with age. Try finding the control and placing a vacuum on it or simply replace this vacuum line with new. That may or may not fix your problem but at least it's a cheap first attempt. Of course, someone who actually knows something about these may give better advice in the meantime.
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