Governor regulation of 3 percent to 5 percent can be attained with the speed droop governor. Precise control of
governor regulation is done by decreasing or increasing the effective length of the governor control spring, this
also decreases or increases the spring control spring rate. The governor control spring is threaded into an adjusting
cap assembly and is referred to as the control rod assembly. By turning the adjusting cap in the clockwise direction,
as viewed from the fuel transfer pump end, the control rod spring shortens and becomes less sensitive, thereby
increasing governor regulation. Turning the adjusting cap in the counter-clockwise direction increases the control
rod spring length and sensitivity which will decrease governor regulation.
The external speed droop adjustment screw, located at the rear of the fuel injection pump housing, controls the
governor sensitivity. The droop screw adjustment varies the governor regulation by changing the effective spring
rate. This adjustment will affect both full load and no load frequency settings and may require that th e high speed
stop screw be reset.
Speed droop adjustments must be made while the engine is operating. After each adjustment of the droop screw,
the engine must be shut down briefly in order to allow the governor spring to unload and the adjusting mechanism
to seek its final position in the spring. Turning the screw in shortens the control spring, making it less sensitive
and increases speed droop. Turning the adjusting screw out has the opposite effect. Speed droop is the fuel
injection pumpโs ability to respond to changing engine loads.
Adjust the governor as follows:
Speed Droop Adjustment
1. Operate the engine until normal operating temperature is obtained (195ยฐF).
Note: If serious surging occurs during the warm-up period, turn the speed droop adjusting screw clockwise until
the surging stops.
2. When the engine reaches operating temperature, position the throttle to attain rated speed and apply 100 percent
load. Adjust the throttle position as necessary to obtain 100 percent performance.
3. Remove the load and check for the specified no-load or, in the case of a generator set, note the frequency. If the
no-load speed is incorrect, loosen the locking cap and adjust the speed droop adjusting screw (clockwise for
increased droop, counter-clockwise for less droop). If surging occurs when the load is removed, turn the adjusting
cap clockwise to eliminate the surge. Tighten the locking cap to secure the adjusting screw.
Note: When the speed droop adjustments are made, it is necessary to adjust the throttle position.
4. Check the 100 percent load and no-load performance again and make adjustments as necessary.