Distributor Advance Unit: Testing and Inspection

1. Warm up the engine fully.
2. Make sure that the idling speed and ignition timing are within specifications.

Idle Speed: 800-850 in park or neutral

Initial timing: 5°-7° BTDC (B2200)
Initial timing: 6°-8° BTDC (B2600)

Fig. 9 Centrifugal spark advance curve:

3. Remove the vacuum hose from the distributor vacuum control unit and plug the hose.
4. While gradually increasing engine rpm, check changes in ignition timing with a timing light Fig. 9.

Excessive advance: Governor spring is fatigued (If the governor spring is broken, the initial advance is very quick and high).

Insufficient advance: Governor weight or cam is not operating properly.