Vacuum Restrictor: Testing and Inspection

NOTE: Ambient temperature in area of vehicle must be above 68 degrees F. for this test.

1. Inspect hose connections and replace any hoses which may allow vacuum leakage.
2. On 1973 vehicles, with engine running at 2,000 rpm in neutral, disconnect hose at OSAC valve leading to distributor and connect a vacuum gauge to this port.
3. On 1974-82 vehicles, with engine at operating temperature and running at 2,000 rpm, "tee" a vacuum gauge into hose leading to distributor.
4. On all vehicles, if a gradual increase in vacuum is observed, about 15-20 seconds, the valve is operating properly. If vacuum immediately goes up to manifold vacuum or there is no vacuum, the OSAC valve is not operating properly and should be replaced.