Runaway engines can occur in diesel engines. A diesel engine does not use an electric ignition system. The high compression of the engine causes the fuel to combust without spark plugs. A runaway engine is the result of air and fuel being feed in excess amounts with no way to slow the engine. As long as the blower (not the turbocharger but the roots type blower) is continuing to blow air into the cylinders and diesel (or motor oil) is being feed uncontrolled to the cylinders the engine will run as fast as it can until either something breaks or the air flow is stopped or the supply of diesel or oil is stopped. If there is an oil leak into the air box (the part of the engine on the outside of the head where the air is forced in by the blower) the engine will start feeding on that oil and burning it in addition to any diesel that is being pumped in by the injectors. This could potentially cause a runaway engine. Many of the industrial use DD mechanical 2-strokes were equiped with an emergency shut off flapper that physically closed off the air intake so the engine would starve from lack of air. The likelihood of a runaway engine in a well maintained coach is very small but, as the article points out, excessive idling can cause the buildup of oil in the airbox. The combination of significant amounts of oil in the airbox with the normal flow of diesel could cause a runaway engine.
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