Ignition System: Description and Operation

DESCRIPTION
Ignition timing control, combined with the internal distributor control (centrifugal advance), affects the time at which each spark plug ignites the air-fuel mixture, in accordance with engine speed, load and coolant temperature. This control system gives vacuum advance in response to the manifold vacuum and coolant temperature. This optimizes ignition timing during and after engine warm-up to maximize fuel economy and engine performance.

OPERATION
The distributor has two separate vacuum advance diaphragms which operate on manifold vacuum. Diaphragm B also has a solenoid valve (ignition control solenoid valve) in the line. It is operated by the ECU which receives signals from the engine coolant temperature, engine speed and manifold vacuum sensors. When the ECU solenoid valve is open, it sends vacuum to Diaphragm B to improve cold engine performance.