Ignition System: Description and Operation

Ignition Circuit:

The ignition system used for this vehicle has an ESA (Electronic Spark Advance) system and consists of the following parts.

^ ECM
It detects the engine condition through the signals from the sensors and determines the most suitable ignition timing and time for electricity to flow to the primary coil and sends a signal to the power unit.

^ IGNITER (POWER UNIT)
It turns ON and OFF the primary current of the ignition coil according to the signal from ECM. At the same time, it send ignition signal (fail safe signal) to ECM. If no fail safe signal is transmitted to the ECM while engine is running, fuel cut operation is executed.

^ IGNITION COIL
When the ignition coil primary current is turned OFF, a high voltage is induced in the secondary winding.

^ DISTRIBUTOR
It distributes a high voltage current to each plug, High-tension cords and spark plugs

^ SPARK PLUGS
Ignites air/fuel mixture in the cylinder.

^ HIGH TENSION WIRES
Conducts secondary voltage from the distributor to the spark plugs.

^ DISTRIBUTOR ROTOR
Routes secondary voltage to the correct terminal of the distributor cap.

^ DISTRIBUTOR CAP
Routes secondary voltage from the rotor to the high tension wires.

^ CAS (CRANK ANGLE SENSOR)
Located in the distributor, it converts the crank angle into voltage variation and sends it to ECM. For its details, refer to COMPUTERS AND CONTROL SYSTEMS.

In ESA system, the ECM is programmed for the best ignition timing under every engine condition. Receiving signals which indicate the engine condition from the sensors, e.g., engine revolution, intake air volume, coolant temperature, etc., it selects the most suitable ignition timing from its memory and operates the igniter. Thus ignition timing is controlled to yield the best engine performance. For more information, refer to COMPUTERS AND CONTROL SYSTEMS.