The ACSD uses the contractive and expansive properties of thermo wax and the tension of a spring to automatically advance the injection timing in response to the coolant temperature, causing the engine to idle-up (fast idle). This improves the startability at low temperatures and the stability of idling.
(1) Cold engine
The thermo wax contracts and pulls the plunger. Lever A rotates clockwise by the spring tension. This causes lever B to push the adjusting lever toward the idle-up position, resulting in a faster idle speed. At the same time, the roller ring is rotated, advancing the injection timing.
(2) Warm engine
As the coolant temperature rises, the thermo wax gradually expands to push the plunger out. Lever A causes the plunger to rotate counter-clockwise, gradually decreasing the advance angle of the injection timing and lowering the idle speed. When the coolant temperature reaches about 5C (12F), both injection timing and idle speed return to normal.
The adjusting method is different between the engine with the ACSD and without the ACSD.