Ignition System: Description and Operation

DESCRIPTION AND OPERATION




The Multiport Fuel Injection System consists of sensors which detect the engine conditions, the ENGINE CONTROL MODULE (ECM) which controls the system based on signals from these sensors and actuators which operate under the control of the ECM.
The ECM carries out activities such as fuel injection control, idle air control and ignition timing control. In addition, the ECM is equipped with several diagnostic test modes which simplify troubleshooting when a problem develops.

IGNITION TIMING CONTROL

The ignition power transistor located in the ignition primary circuit turns ON and OFF to control the primary current flow to the ignition coil. This controls the ignition timing to provide the optimum ignition timing with respect to the engine operating conditions. The ignition timing is determined by the ECM from the engine speed, intake air volume, engine coolant temperature and atmospheric pressure. When the engine is cold the ignition timing is slightly advanced to provide optimum performance to the operating condition.

IGNITION SYSTEM OPERATION NOTES

- Turn ignition switch to "ON" position, and battery positive voltage will be applied to primary winding of ignition coil (incorporated into the distributor).
- The engine control module detects the crankshaft position by the crankshaft position sensor installed at the front end of the crankshaft.
- When the crankshaft position sensor signal is input to engine control module, ON-OFF control of ignition power transistor is performed by engine control module.
- When ignition power transistor is turned on, current flows from the ignition coil (primary winding) to ground through the ignition power transistor.
- When the ignition power transistor is turned off, high voltage is generated in the primary winding of ignition coil which induces even higher voltage in the secondary winding. The high voltage thus generated is directed by the distributor to the applicable spark plug igniting the compressed air fuel mixture in the combustion chamber.
- The cylinder firing order is 1 - 3 - 4 - 2