Ignition Glossary
Alternator: An electricity-generating device that converts mechanical energy to electrical energy in the form of alternating current. Diodes rectify the alternating current into direct current.
Capacitor discharge ignition system: An ignition system that stores its primary energy in a capacitor.
Coil: A term often used to describe an ignition coil.
Distributor: A device used to direct electrical current to spark plugs.
Distributor advance: A term used for centrifugal advance, ignition advance, or vacuum advance.
Distributor cap: A cover for the conventional ignition-system distributor, having a central terminal that receives secondary voltage from the coil and four, six, or eight peripheral terminals to send this voltage to the spark plugs.
Distributor housing: A metal part that contains or provides a mounting for distributor components in a conventional ignition system.
Distributorless ignition system: An ignition system that relies on a computer to distribute the electrical spark to the proper spark plug.
Electric system: Any of the systems and sub systems that make up the automobile wiring harnesses, such as the lighting system or starting and charging system.
Electronic ignition (EI): An ignition system where a solid state device has replaced mechanical breaker points.
Electronic ignition system: An ignition system controlled by the use of small electrical signals and various semiconductor devices and circuits.
Engine-management system: An electronic device that monitors, adjusts, and regulates the ignition and fuel-injection systems to maintain engine control under varying operating conditions.
Ignition: The firing of a spark plug to ignite the air/fuel mixture in the combustion chamber.
Ignition advance: The moving forward, in time, of the ignition spark relative to the piston position.
Ignition coil: A transformer containing a primary and secondary winding that acts to boost the battery voltage of 12 volts to as much as 30,000 volts to fire the spark plugs.
Ignition distributor: A term used for distributor.
Ignition map: A chart showing the precise advance and retard of the ignition on an electronic control-equipped engine.
Ignition switch: A five-position switch that is the power distribution point for most of the vehicle's primary electrical systems. The spring-loaded START position provides momentary contact and automatically moves to the RUN position when the key is released. The other switch detent positions are ACCESSORIES, LOCK, and OFF.
Ignition system: The major components, such as the battery, coil, ignition switch, distributor, high-tension wiring, and spark plugs, that provide the right spark at the right time to ignite the air/fuel mixture.
Ignition timing: The timing of the spark, expressed in crankshaft degrees, in relation to top dead center.
Rotor:
- In a conventional ignition system, the part that transfers the secondary voltage from the central terminal to the outer terminals of the distributor cap as it rotates inside the cap.
- The rotating part of an alternator that provides the necessary magnetic field to create a current flow.
Solenoid relay: A relay that connects a solenoid to an electrical circuit, such as a starter-motor solenoid relay.
Spark advance: The moving ahead of the ignition spark in relation to the piston position.
Spark duration: The time a spark is established across the gap of a spark plug.
Spark plug: An ignition component threaded into the cylinder head that contains two electrodes extending into the cylinder that form a gap across which high-voltage electricity arcs to ignite the compressed air-fuel mixture.
Spark plug fouling: An accumulation of deposits on the lower, exposed end of the spark plug that act as an electrical conductor, thereby creating a path for electricity to leak to ground rather than jump across the electrode gap.
Spark plug heat range: The temperature limits hot, normal, or cold, within which a spark plug is designed to operate. It is determined by varying the length of the exposed lower section of the plug ceramic insulator.
Spark plug well: The recess in a cylinder head for a spark plug.
Spark plug wire: A special high-voltage wire from the distributor cap to the spark plug.
Spark retard: To cause ignition spark to occur later in an engine's cycle.
Timing light: A stroboscopic tool used to check the precise timing of a conventional ignition, adjusted by loosening the holddown bolt and turning the distributor.
Twin-plug ignition system: An ignition system having two distributors, two coils, and two plugs per cylinder.
