Ignition Timing Control System

WITH ENGINE COLD

NOTE: Engine coolant temperature should be below thermovalve B set temperature of 59 deg. F.

1. Disconnect vacuum hose No. 2 from vacuum advance diaphragm B on distributor, then connect suitable vacuum gauge to hose.
2. Start engine and allow to idle. If vacuum is present, test system with engine hot. If vacuum is not present, replace thermovalve B and repeat test.

WITH ENGINE HOT

1. Connect suitable tachometer, then disconnect vacuum hose No. 2 from vacuum advance diaphragm B on distributor and connect suitable vacuum gauge to hose.
2. Start engine and allow to reach normal operating temperature. At idle, vacuum should not be present.
3. If vacuum is not present, proceed to step 5. If vacuum is present replace thermovalve B.
5. Attach hand vacuum pump to vacuum advance diaphragms A and B using a suitable T-fitting.
6. Plug ends of vacuum hoses, then pinch off hose to diaphragm B.
7. Start engine, apply 16 inches Hg. vacuum and record timing. Timing should advance and remain steady.
8. If timing advances, proceed to step 9. If timing will not stay advanced, replace advance diaphragm and repeat test. If timing does not advance, stop engine and remove distributor cap. Inspect breaker plate for free movement. If no binding is evident, replace advance diaphragm and repeat test.
9. Release pinched hose and apply 16 inches Hg. vacuum. Timing should advance more than recorded in step 7 and remain steady.
10. If timing advances more than previous test, system is satisfactory. If timing does not advance more than recorded in step 7, replace advance diaphragm and repeat test.