Operation of a Governor:

The following is an explanation of the operation of a constant speed, hydraulically compensated governor using the Woodward brand governor as an instance. The principles included are general in any mechanical and hydraulic governor.

The Woodward speed governor operates the diesel engine fuel racks to ensure a constant engine speed is maintained at any load. A governor is a mechanical-hydraulic category governor and receives its supply of oil from the engine lubricating system. That means that a loss of lube oil pressure will cut off the supply of oil to the governor and cause the governor to shut down the engine. This gives the engine within a built-in shutdown device to protect the engine in the event of loss of lubricating oil pressure.