Operation CHARM: Car repair manuals for everyone.

Spark Control System

Fig. 18a Coasting Air Valve System:




Fig. 19b Air Switching Valve System:




Fig. 16 Deceleration spark advance system:




Fig. 17 Dashpot adjustment:






PURPOSE
The deceleration systems reduce HC emissions during deceleration.

The deceleration system may include;
- A Coasting Air Valve (CAV) System, Fig. 18a
- An Air Switching Valve (ASV) System, Fig. 19b
- A Deceleration Spark Advance System (DSAS), Fig. 16
- And/or A Dashpot, Fig. 17.

CAV & ASV SYSTEMS OPERATION
These systems are controlled by the engine speed sensor through activation of the solenoid valve.

During deceleration
At engine speeds within the specified range;
- The engine speed sensor energizes the solenoid valve.
- The CAV system supplies additional air to the intake manifold, from a port located below the secondary throttle valve.
- The ASV supplies additional air to the intake manifold, from the idle mixture adjusting screw passage located below the primary throttle valve.

At or below the specified engine speed the engine speed sensor deactivates the solenoid valve--to prevent poor idling or engine stalling.

DSAS SYSTEM OPERATION
This systems is controlled by the engine speed sensor through activation of the solenoid valve.

During deceleration
At engine speeds within the specified range;
- The engine speed sensor deactivates the solenoid valve.
- The DSAS Fig. 16 advances ignition timing by allowing intake manifold vacuum--routed through the solenoid valve--to act upon the distributor vacuum advance unit diaphragm.

At or below the specified engine RPM, the engine speed sensor will activate the solenoid valve, changing vacuum acting upon the distributor vacuum advance unit diaphragm from intake manifold vacuum to carburetor ported vacuum.

Specified Engine Speed
- On 1,400, 1,600 and 2,000 cc engines, the specified engine speed is 1,800 RPM (+/- 200 RPM).
- On 2,600cc engines, the specified engine speed is 1,600 RPM (+/- 200 RPM).

DASHPOT OPERATION
On some models a dashpot is used to delay throttle valve closure during deceleration to its normal idle speed position to reduce HC emissions.

CONSTRUCTION
The CAV and ASV are built into the carburetor.