Spark Control System

This system is used to control vacuum signals to the distributor main and/or sub-advance diaphragms in order to reduce HC and NOx emissions, speed warm-up of the catalytic converter and/or improve cold engine driveability.

When coolant temperature is below approximately 77-86°F, the bi-metal vacuum switching valve is off and there is no main vacuum advance.

When coolant temperature is above approximately 106-111°F, the bi-metal vacuum switching valve is open and timing is advanced normally.

Component Testing


CHECK VALVE
All models do not use a check valve, refer to application charts for usage.
1. Blow air into each pipe.
2. Air should flow freely from white or orange pipe to black pipe, but no air should flow from black pipe to white or orange pipe.

BI-METAL VACUUM SWITCHING VALVES

3E & 22R ENGINES
1. Drain coolant.
2. Remove bi-metal vacuum switching valve.
3. Using cool water, cool valve to below 86°F, on 22R engines or 77°F, on 3E engines.
4. Blow air into either pipe and ensure air does not flow from other pipe.
5. Using hot water, heat valve to above 111°F, on 22R engine or 106°F, on 3E engine.
6. Blow air into either pipe and ensure air flows freely from other pipe.
7. If air flow is not as described, replace valve.
8. Apply suitable sealer to valve threads and install valve.
9. Fill radiator with coolant.

VACUUM TRANSMITTING VALVE
1. Ensure air flows freely from one side to the other.
2. Ensure air flows with great resistance in other direction.
3. If air flow is not as described, replace valve.