Lesson3/Learning Event 1
The ignition system not only builds up these high-voltage surges to fire the fuel-air mixture in the
engine cylinders, it also times or paces these surges so they will occur in each cylinder just as the
piston reaches the end of its compression stroke. So we can say that the ignition system has the
job of building up high-voltage surges and timing them to occur in each cylinder at precisely the
right instant. How this is done is the story of each ignition system.
The intent of this lesson is to provide you with a knowledge of the construction and operation of
the components in an ignition system that provide the spark needed to make an engine run.
BATTERY IGNITION SYSTEM COMPONENTS
Although other things are usually added, the basic ignition system consists of the following items:
The vehicle's battery or batteries and the generator to supply the required current. While the
engine is being cranked, the batteries supply the low-voltage current to the ignition system. When
the engine is running and the generator is charging, it takes over the job of supplying current to the
The ignition switch opens and closes the circuit between the batteries and the other components in
the ignition system. We usually stop the engine by turning off (opening) the ignition switch.
The ignition coil is the device that converts the low voltage from the batteries to the high voltage
needed to ignite the fuelair mixture in the engine cylinders.
The ignition distributor alternately opens and closes the low-voltage circuit through the coil. It also
receives high-voltage surges from the coil and distributes them to the proper cylinders to burn the
fuel-air mixture. The low-voltage circuit is better known as the primary circuit, while the high-
voltage circuit is better known as the secondary circuit. In the remainder of this lesson, we will
refer to them as the primary and secondary circuits.
High-tension (voltage) wires carry high-voltage surges to the spark plugs.