Distributor Vacuum Control: Testing and Inspection

Fig. 71 Vacuum advance chart.:

1. Warm engine to operating temperature.
2. Ensure idle RPM and ignition timing are within specification.
3. With engine idling, disconnect vacuum hose(s) to vacuum control and plug end of hose(s).
4. Attach vacuum pump to control port(s) and check with timing light while applying vacuum Fig. 71.