Lesson 2/Learning Event 1
Engine speed in a diesel engine is controlled by the amount of fuel injected; consequently, the injection
system is designed to supply the maximum amount of fuel which will enable the engine to operate at full
load and reach a predetermined maximum speed (RPM). However, if the maximum fuel charge is supplied
to the cylinder when the engine is operating under partial load or no load, the engine will overspeed and
soon cause failure.
All diesel engines require governors to prevent overspeeding of the engines under light loads. Automotive
diesel engines also demand control of the idling speed. Governors provide variable speed control. Besides
controlling minimum and maximum speeds, they will hold any intermediate speed desired by the operator.