Distributor Advance Solenoid Valve

Distributor Vacuum Advance System:

The distributor vacuum advance is a dual diaphragm type having main vacuum chamber and sub-vacuum chamber. For primary control of the ignition timing, the ECU utilizes the Main Vacuum Chamber (controlled by the distributor advance solenoid valve). When the engine speed is near the idle speed (below 1,200 RPM), the ECU energizes the distributor advance solenoid valve. By this action the carburetor D port vacuum is ported to the main vacuum chamber. At idle the D port vacuum is zero. Vacuum increases as throttle valve opening angle increases. When the engine speed increases to 1,200 RPM the ECU de-energizes the distributor advance solenoid valve. This ports intake manifold vacuum to the main vacuum chamber, increasing ignition advance. During engine warm up, temperatures below 80°C (176°F), the solenoid remains energized, allowing D port vacuum to remain ported to the main vacuum chamber.