Horsepower requirements of an engine may vary continually due to the fluctuating loads; therefore, some means must be
provided to control the amount of fuel required to hold the engine speed reasonably constant during such load fluctuations.
To accomplish this control, one of three types of governors is used on the engines. Installations requiring maximum and
minimum speed control, together with manually controlled intermediate speeds, ordinarily use a limiting speed mechanical
governor. Applications requiring a near constant engine speed under varying load conditions, that may be changed by the
operator, are equipped with a variable speed mechanical governor. The hydraulic governor is used where uniform engine
speed is required under varying load conditions with a minimum speed droop.
The mechanical governors are lubricated by oil splash from the engine gear train. Oil entering the governor is directed by
the revolving governor weights to the various moving parts requiring lubrication.
The hydraulic governor is lubricated by oil under pressure from the engine.
Governor difficulties are usually indicated by speed variations of the engine. However, speed fluctuations are not
necessarily caused by the governor and, therefore, when improper speed variations become evident, the unit should be
checked for excessive load, misfiring or bind in the governor operating linkage. If none of these conditions are contributing
to faulty governor operation, contact an authorized Detroit Diesel Allison Service Outlet.