1985 300D

I did a search and still need help.

My car will not switch off. I can stop the car with the "Stop lever" but would like to fix the problem. I have read that the "solenoid" may be bad. The solenoid is silver and is on the injector pump right? It has two hoses coming out of it. one clear one black. In the search it said to test by covering the hose connection with your finger and pushing the stop lever. The clear connection or the Black connection? With the car running or off? What else could I try??

Please help