Solenoid Valve
Disconnect vacuum advance line from distributor and connect to vacuum gauge. Start engine and raise idle to 1500-2000 RPM. Vacuum gauge should read normal vacuum while engine is cold. After temperature rises and before radiator fan starts, vacuum gauge should drop to zero. With engine cold, if no vacuum is available, stop engine and disconnect vacuum signal line from idle cut-off valve at charcoal canister and plug line. Restart engine and set to fast idle. If vacuum is not available, check idle cut-off valve (see appropriate story in Evaporation Emission Section). If vacuum is still not available, stop engine and disconnect vacuum line to manifold from solenoid valve and insert vacuum gauge. If vacuum is now available, solenoid valve is defective. Replace and recheck. If vacuum is not available, vacuum port is restricted. Clean port with compressed air.