Spark Control Systems Diagnosis & Testing

CTO VALVE

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1. disconnect vacuum hose from distributor vacuum advance mechanism and connect a suitable vacuum gauge to the hose.
2. Start and run engine. With coolant temperature below 120° F, manifold vacuum should be indicated on gauge.
3. Disconnect vacuum hose from port 4 of delay valve and cap the port. The gauge should not indicate manifold vacuum until coolant temperature reaches approximately 120° F.
4. Stop engine, remove cap from port 4 of delay valve and vacuum gauge and reconnect vacuum hoses. If defective, replace valve.



VACUUM SPARK DELAY CONTROL VALVE

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1. Connect tee fittings to ports 1 and 4, then connect a suitable vacuum gauge to each tee fitting.
2. Start engine and check vacuum gauges. Vacuum should be equal.
3. Quickly depress throttle. Vacuum at port 1 should decrease instantly and vacuum at port 4 should be maintained momentarily.
4. Stop engine and remove gauges and tee fittings. If defective, replace valve.




THERMAL VACUUM SPARK CONTROL VALVE

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1. Disconnect vacuum hose from port 1 of CTO valve and connect a suitable vacuum gauge to the disconnected hose.
2. Start and run engine. With air cleaner intake air temperature below 63° F, manifold vacuum should be indicated on the gauge. When intake air temperature is above 63° F, no vacuum should be indicated on the gauge.
3. Stop engine and remove vacuum gauge. If defective, replace valve.