How the ignition system works

The ignition system is employed to generate a very high voltage (from 18 to 30 thousand volts) to jump across the spark plug gap to ignite the air-fuel mixture inside the combustion chamber of a gasoline engine.The ignition system consist of two main circuits.

1. PRIMARY CIRCUIT:

Primary circuit is also called the low voltage or the low tension circuit. This is the circuit through which current flows at battery or generator voltage. The ignition switch, resistor, ignition coil primary winding, breaker points and the condenser are all in the primary circuit.

2. SECONDARY CIRCUIT:

The secondary ignition circuit is also called the high voltage or high tension circuit. The coil secondary winding, distributor rotor, distributor cap, high tension leads, and the spark plugs are all part of the secondary circuit.

THE IGNITION SYSTEM

HOW IGNITION SYSTEM WORKS:

When the ignition switch is turned on and the breaker points are closed, current flows in the primary circuit. As current flows through the primary winding of the ignition coil, a strong magnetic field is produced in the coil. When the breaker points open, current through the primary winding of the coil is stopped, and the magnetic field around the coil winding collapses. These collapsing lines of force cut across both the primary and secondary winding inducing a very high voltage in the secondary winding. The high voltage so induced current to jump the spark plug gap.

The primary ballast resister is essentially a current compensating device consisting of a resistor unit or wire located in the primary ignition circuit. The compensating action is obtained because, at low engine speeds, the current flows for longer period of time. This heats up the resistor, thereby raising its resistance and reducing current flow. This action serves to keep the coil primary winding cooler and improves distributor breaker point life. At high speeds, the current flows for shorter periods of time which lets the resistor cool and increases the current flow in the primary winding of the coil. This action permits maximum secondary voltage to be obtained.

Because of the lowered battery voltage resulting from the starter load on some vehicles, the ballast resister is bypassed while the starting system is in operation. This is done to provide higher secondary voltage for starting.