Vacuum Vent Valve
The vacuum vent valve provides the make-up air for the air pump system retard delay valve and air by-pass valve during idle modes to deactivate the air pump system after a controlled period of time.
Application of vacuum from the carburetor to both ports of the vacuum vent valve causes the diaphragm in the valve to initially move left and seat the dump valve. In this position, vacuum is applied to the rest of the system.
During idle, this vacuum application is removed. The diaphragm moves right. The dump valve leaves the seat, opening the vent and allowing air to enter the system to reduce the vacuum previously applied to the retard delay valve.