Now for a look at the operation of the assembly that controls the engine speed at low idle and high speed. The Min-Max governor.
Illustrated here (Figure 4-70) are the main components of the governor. They are the governor weights, the governor arm, the low idle spring, the idle spring guide, the main governor spring, the main governor spring guide and the guide stud.
Low Idle
Figure 4-71 shows the relationship of the parts when the pump is running at low idle. The low force developed by the governor weights is balanced by the low idle spring. Thus, only a small amount of fuel is delivered by the metering valve.
Mid-Range
In Figure 4-72, the throttle is in a mid-range position. The idle spring is fully collapsed, and the governor weights have moved out partially. The main governor spring is designed such that the governor weight force cannot overcome the springโs preload until the engine reaches the maximum rated speed. Thus, at partial throttle, the assembly acts as a solid link against the governor arm. This permits the driver to control the metering valve position with the throttle over the entire mid-range speed.
Full Load
With the throttle in the full load position, the engine speed and the pump speed increase until the governor weights have generated enough force to deflect the main governor spring. This movement turns the metering valve to the shut-off position, thereby preventing an engine overspeed condition. (Figure 4-73).
