How Your Car’s Ignition System Works

The ignition system creates an electric spark that ignites the fuel-air mixture in the cylinder’s combustion chamber. Because the ignition system is so crucial to the proper running of your vehicle, it is one of the most important things to be checked during a car service. In this article, we’ll take a closer look at the ignition system, including the different types of ignition systems and the parts that constitute them.

Key parts of an ignition system

The ignition system consists of:

• The battery, which feeds electrical current to the ignition coil.
• The ignition coil, which transforms the 12 volts from the battery into the thousands of volts required to initiate the spark.
• The distributor, which sends the high voltage from the coil to the spark plugs, controlling the timing to ensure they spark at the right time.
• The spark plugs, which fit into the head of the engine cylinders and ignite the fuel when the piston is at the top of its compression stroke.

How the ignition system works

It all begins in the ignition coil, which takes the relatively weak power generated by the battery and turns it into a spark strong enough to ignite a fuel vapour. What we refer to as the coil is actually a combination of two wire coils — the primary and the secondary. The primary coil or “winding” carries the low voltage from the battery and the secondary coil transforms it into high voltage before sending it to the distributor.

The distributor takes the high voltage electricity generated by the ignition coil and sends it through the rotor — a spinning part that makes contact with each of the spark plug wires. The spark plug wires deliver the voltage to their connected spark plugs in each cylinder of your engine, igniting the fuel vapour during the combustion stroke. This process repeats thousands of times per minute, powering your car.

Three types of ignition systems

There are three different types of ignition systems. These include:

• Point-type ignition system. The traditional ignition system, which we’ve defined above.
• Electronic ignition system. Similar to the point ignition system, its difference lies in the distributor component. Instead of a cam, breaker plates, condenser and points, the electronic system has something called an armature, a pickup coil and an electronic control module. Electronic ignition systems were a response to the quest for greater mileage and reduced vehicle emissions in the modern driving environment. Because the spark created by an electronic ignition system is greater than point type, less fuel is needed with each stroke.
• Distributorless ignition system. This type of ignition system gets rid of the distributor altogether, instead firing the spark directly from the coils to the spark plug. The timing is controlled electronically by the ignition control unit (ICU) and engine control unit (ECU).

Common ignition system problems

If the ignition timing is even the slightest bit incorrect, it may cause the spark to ignite at the wrong time. In a working system, the spark ignites during the combustion stroke of the engine — that is, just after the piston has compressed the fuel-air mixture and as it is making its way back down. If the spark ignites too early, the fuel will expand too soon, forcing the piston down while it’s still travelling up and causing the engine to make a metallic pinging sound. If the spark ignites too late, maximum cylinder pressure will occur after the piston is on its way down the cylinder, result in less power and higher emissions. If you suspect something is wrong with your ignition system, you should see a mechanic as soon as possible.