The vacuum pump is controlled by the vacuum switch built into the valve assembly tank, and is used to supply the vacuum to the tank. Power to the pump is fed when the vacuum switch is turned ON, and the diaphragm is moved up and down by the rotation of the offset shaft fixed to the motor shaft.
The vacuum valve, vent valve, and safety valve provide the open-close operation which leads to the vacuum/atmospheric pressure to the actuator. Also attached to this assembly is the tank for storing vacuum generated by the pump, and the vacuum switch for controlling the pump to maintain a constant vacuum level in the tank.
If the cruise control is turned ON and a constant vehicle speed is attained, the safety valve connected to the atmosphere is closed. Also, the vacuum valve connected to the tank and the vent valve connected to the atmosphere operate to lead the atmosphere/vacuum to the actuator. When the cruise control is canceled, the vacuum valve closes to shut off the tank vacuum, and the safety valve opens to allow atmospheric pressure to enter the actuator.
The vacuum in the tank is consumed by the operation of the vacuum valve. If the vacuum in the tank reaches 13 in. Hg (43 kPa) the vacuum switch is turned ON, and the pump feeds the vacuum into the tank. When the vacuum in the tank reaches 15 in. Hg (52 kPa) the vacuum switch turns OFF to stop the pump.
The diaphragm is operated by vacuum or atmospheric pressure led by each valve, and this diaphragm movement actuates the wire cable through the link assembly to open or close the throttle valve. With the cruise control set to OFF (system OFF state), no diaphragm operation occurs as the atmospheric pressure is kept inside the actuator.
The throttle body or carburetor is equipped with 2 throttle cams. One cam is used during acceleration and the other during cruising, in order to open or close the throttle valve. These cams operate independently of each other. In other words, while 1 cam operates, the other does not.