The all-speed governor controls the fuel injection volume at all engine speed ranges. The spill ring is moved by the governor, changing the effective stroke, resulting in an adjustment of the injection volume.
1. Starting
When the accelerator pedal is depressed and the adjusting lever is moved in full-load direction at the time of starting, the control spring pulls the tension lever until it contacts the stopper. Because the pump speed is low at starting and the centrifugal force of the flyweights is extremely small, even the start spring (a plate spring), which has a small tension, is able to push the control lever against the governor sleeve, thus causing the flyweights to close completely. At this time, the control lever rotates counter-clockwise around fulcrum A and moves the spill ring to the start position (maximum injection volume) in order provide the fuel injection volume that necessary during starting.
2. Idling
After the engine is started and the accelerator pedal is released, the adjusting lever returns to the idle position. Because the tension of the control spring at this time is practically zero, the flyweights can expand outward despite the low speed. As a result, the governor sleeve compresses the idle spring. At this time, the control lever rotates clockwise around fulcrum A, to move the spill ring to the idle position. In this manner, a smooth idling speed can be realized when the centrifugal force of the flyweights and the tension of the idle spring are balanced.
3. Full-load (accelerator pedal fully depressed)
When the accelerator pedal is fully depressed, the adjusting lever moves to the full-load position and the tension lever comes in contact with the stopper, similar to the starting. In this situation, the control spring has a high tension and the damper spring is completely compressed and inactive. Unlike the starting, a strong centrifugal force acts on the flyweights, and the governor sleeve pushes the control lever to the right. Then the control lever rotates clockwise around fulcrum A, until fulcrum B comes in contact with the tension lever, thus moving the spill ring to the full-load position. Consequently, the injection volume at this time will be less than during starting.
4. Maximum speed (accelerator pedal fully depressed)
When the engine speed becomes greater than the specified speed, the centrifugal force of the flyweights becomes greater, which causing the force that is applied to the governor sleeve to become greater than the tension in the control spring. Then the control lever and the tension lever move in unison, rotating clockwise around fulcrum A, in order to move the spill ring in the direction that decreases injection volume. By restricting the maximum speed in this manner, the engine is prevented from overrunning.
5. Partial load (medium speed) (accelerator pedal depressed halfway)
When the adjusting lever is in the intermediate position between fullload and idling, the control spring has a weak tension, allowing the spill ring to move in the direction that decreases the injection volume at a lower speed than during the maximum speed control. As a result, the engine speed is controlled in accordance with the level of depression of the accelerator pedal. The characteristic of the injection volume in this situation is the same as during the full-load when the engine speed is low (before the spill ring is moved in the direction for decreasing the injection volume). As the speed increases thereafter, the injection volume decreases in order to control the speed.