Distributor: Description and Operation

Fig. 12 Spark Advance Control System:

The spark advance control system controls the vacuum flow from the intake manifold to the vacuum advance unit at the distributor. This is done by adding a vacuum advance solenoid valve (VASV) inline to the vacuum advance line. The VASV can open or close the vacuum flow to the vacuum advance unit at the distributor. The VASV is controlled by the vacuum advance control unit.
The vacuum advance control unit utilizes the input of the intake air temperature sensor, coolant temperature switch and injection control module to determine when the VASV should be open or closed.




COMPONENTS:


Vacuum Advance Solenoid Valve (VASV):
The VASV opens or closes the vacuum flow to the vacuum advance unit at the distributor. The VASV is located at the firewall, above brake vacuum booster.


Vacuum Advance Control Unit:
The vacuum advance control unit utilizes the input of the intake air temperature sensor, coolant temperature switch and injection control module (engine load input) to determine when the VASV should be open or closed. The control unit is located on the bracket in front of left front shock tower.


Coolant temperature switch:
The coolant temperature switch closes an electrical circuit when the water temperature reaches 45°C (113°F). The closed circuit is used as an input signal for the vacuum advance control unit. The switch is located in front of engine on thermostat housing.


Intake air temperature sensor:
The intake air temperature sensor sends an input signal to the vacuum advance control unit. The sensor is located below the air cleaner in left front corner of engine compartment.