In this section of the chapter, we will discuss the methods and the devices that serve to control the output of the injection pumps and injectors. By controlling the output of the fuel injector system, these devices ensure control of engine operation.

GOVERNORS

A governor is a speed-sensing device on an engine that serves to maintain a constant speed (in rpm) within the design power rating of a diesel engine. A governor may also serve to limit high-and low-idle revolutions per minute of the engine. All governors used on diesel engines control engine speed by regulating the amount of fuel delivered to the cylinders. An example of engine control without the use of a governor is in the conventional automobile-the engine speed and engine load changes are sensed by the driver. The drivers movement of the throttle is an extension of a conditioned reflex; in other words, the driver acts as the governor. However, the driver will not be capable of reacting to load and speed changes quickly enough insofar as the diesel engine is concerned. This is because a diesel engine can accelerate at a rate of more than 2,000 rpm to meet certain requirements. The exacting duty of maintaining a constant speed is better accomplished by a governor.

Figure 9-26.-Simple mechanical governor.