What Causes Diesel Engine Overspeeding?
2 Answers
Diesel engine overspeeding is caused by: excessive fuel supply and oil burning. When overspeeding is caused by excessive fuel supply, black smoke will be emitted from the exhaust pipe, and it can generally be stopped by cutting off the fuel supply. When overspeeding is caused by oil burning, blue smoke will be emitted from the exhaust pipe, and cutting off the fuel supply alone is not effective in stopping it. In this case, the air supply must also be cut off and rapid decompression must be applied to stop it. Methods to handle diesel engine overspeeding: 1. Place the speed control handle (pedal) in the no-fuel supply position; 2. For fuel injection pumps with exposed fuel supply rods or rack bars, quickly pull the rod back to the no-fuel supply position; 3. For engines with decompression devices, quickly place the decompression handle in the decompression position; 4. For intake manifolds with valves, quickly close the valve. For those without valves, remove the air filter cover and block the intake manifold with an object.
Last time I had my car repaired, I encountered a diesel engine runaway - absolutely terrifying. The RPM suddenly skyrocketed, with black smoke pouring from the exhaust pipe. The most common cause is governor failure - that little component responsible for controlling RPM. If its spring breaks or gets stuck, the throttle can't return. Older vehicles are more prone to this issue, so pay special attention to carbon buildup in the fuel system clogging the injection pump plunger. Another easily overlooked factor is burning engine oil - when cylinder wear becomes severe, crankcase oil can enter the combustion chamber and burn as fuel, causing RPM to surge wildly. If this happens, don't panic - immediately shut off the fuel valve or block the air intake, otherwise the engine could be completely destroyed. Regular checks of air filters and fuel lines are crucial.
