Test Description

1. Check that vacuum hoses are properly connected and distributor vacuum controller functions normally, then connect timing light.
2. Check timing with engine cold.
3. Warm up engine. Timing should retard as engine warms up.
4. Check timing with engine at operating temperature. Timing should advance.
5. If timing does not change, replace thermal vacuum valve.
6. Apply vacuum. Timing should retard. If not, replace vacuum control valve.