Ignition System: Description and Operation
GENERAL DESCRIPTIONThe ignition circuit consists of the battery, distributor, ignition switch, spark plugs, and primary and secondary wiring. This vehicle utilizes a distributor ignition system which is monitored and controlled by the engine control module ECM/PCM powertrain control module.
DISTRIBUTOR IGNITION SYSTEM
The ignition will incorporate the use of a crankshaft position sensor (CKP) and an externally mounted igniter. All spark timing changes in the distributor are performed electronically by the engine control module ECM/PCM powertrain control module. The ECM/PCM monitors information from various engine sensors, computes desired spark timing, and signals the distributor to change the timing accordingly. No vacuum or mechanical advance mechanisms are used. The ignition system also includes a capacitor to eliminate ignition sound.
SECONDARY WIRING
The spark plug wiring withstands high temperatures and provides an excellent insulator for the high voltages produced by the distributor ignition system. The spark plug boot forms a tight seal on the spark plug and should always be twisted one-half turn before removing the spark plug wire. Care should also be exercised when using a timing light or other pickup equipment. Do not force anything between the boot and the wiring. Connections should be made in parallel using an adapter. Do not pull on the wire to be removed. Pull on the boot or use a tool designed for this purpose.
SPARK PLUGS
This vehicle should be serviced with NGK Type BKR5EYA or Nippondenso Type K16R-U spark plugs. The spark plug gap should be set to 0.8 mm (0.031-inch). Normal service is assumed to be a mixture of idling, slow-speed and high-speed driving. Occasional or intermittent highway driving is needed for good spark plug performance. The higher combustion temperatures generated during highway driving burn away carbon and oxide deposits that have built up from frequent idling or continuous stop-and-go driving.
Spark plugs must operate within certain temperature limits to provide the performance and service life expected. The spark plug selected for an engine is based only on normal engine service, and may not apply for abnormal engine service conditions. For instance, a spark plug one step hotter in heat range might deliver longer service life than the spark plug recommended for almost exclusive city driving. Conversely, a spark plug one step colder than recommended will perform better for continuous high speed driving.
There are three rules to follow when selecting spark plugs for an engine in good condition:
1. Select a spark plug with the specified heat range.
2. Should spark plug overheating occur, choose a spark plug that is one heat range colder than the specified heat range.
3. If fouling is a problem, select a spark plug that is one heat range hotter than the specified heat range.
IGNITION SWITCH
The ignition switch is located on the right side of the steering column below the steering wheel. The electrical and mechanical portions of the switch work in conjunction with each other.