Ported Vacuum Switches: Testing
- Make certain all vacuum hoses are properly routed and installed. Attach a tachometer to the engine. Bring engine up to normal operating temperature. Ensure choke is fully open. Do not overheat engine.
- Record engine idle RPM with transmission in neutral. Disconnect vacuum hose from intake manifold at PVS and plug hose.
- Note engine idle RPM with hose disconnected. If no change is evident, valve is OK up to this point. If there should be a drop of 100 RPM or more, replace PVS.
- Reinstall vacuum line on intake manifold. Be sure coolant level and mixture is correct. Check for proper radiator pressure cap. Cover radiator sufficiently to induce a high temperature condition.
- Run engine until temperature light comes on, or until temperature gauge is at high end of scale. Engine speed by this time should have increased by 100 RPM or more. If not, replace PVS. Take care not to excessively overheat engine.
Courtesy of FORD MOTOR CO.