As diesel engines will “run on the smell of an oily rag” and they don’t have spark plugs to ignite the combustion charge. They actually fire the combustion charge with compression heat alone. Because of this they can “run away” by themselves if they bypass to much oil or suck flammable gases through the intake system when running.
You can’t just turn the key off with diesel engine!
Watch how these unsuspecting owners freak out at this diesel phenomenon.