Mechanical governor

The mechanical governor controls the fuel injection quantity depending on the engine speed instead of controlling it electronically. The governor controls the fuel injection quantity by adjusting the position of the injection pump's control rack.
The governor enables a constant engine speed to be maintained even if engine load were to fluctuate.
When a governor is used, the control rack operates automatically to increase fuel injection, which returns the engine speed to the desired speed.

The internal components of the mechanical governor include the control rack of the injection pump, the fork lever, accelerator lever, governor spring, sleeve, governor shaft, weight, etc.

The governor functions by balancing two opposing forces.
The spring attached to the fork lever is tensioned by accelerator or throttle control.
This operates the control rack, which increases the fuel injection.
When the governor rotates the weight, the weight is pushed out by centrifugal force.
The weight pushes the sleeve, after which the sleeve pushes the fork lever to decrease the fuel injection.
Accelerator or throttle control is kept constant, and if engine load is increased, the engine speed drops.
This causes the governor force on the fork lever to decrease and the fork lever to be tensioned by the spring force of the accelerator, in turn increasing fuel injection.

Because the governor weight will push the fork when the engine speed increases, fuel injection will decrease. By maintaining this equilibrium, the governor keeps the engine speed constant regardless of fluctuations in engine load.