How Distributor Ignition Coils Work

Ignition coils are crucial to an engine's ignition system. They turn the battery's relatively low voltage (typically 12 volts) into a high voltage needed to ignite an air-fuel mixture in each cylinder.

When your car's ignition coil is in good working order, your vehicle will run smoothly and efficiently with no issues or problems. However, sometimes it may fail prematurely or become faulty and cause the engine to misfire, backfire, or give poor gas mileage. If you're experiencing any of these symptoms, you should have your distributor checked and replaced.

How an Ignition Coil Works

For decades, engines relied on a simple system of electrical conversion between the battery's low voltage and the high voltage required to ignite an air-fuel mixture in each of the engine's cylinders. This was done by an ignition coil connected to a distributor's rotor, which would spin and create a pulse arc.

This arc would travel through a distributor cap and then to each of the spark plug wires, which would then run through the cylinder head into each cylinder. Then, that spark plug wire would be energized and the spark would ignite the air-fuel mixture inside the cylinder and power the engine.

In modern vehicles, the ignition process is much more complex. It is based on the use of a distributor and electronic controls to ensure that the correct spark is transferred to each spark plug in the correct firing order at exactly the right time.

The distributor is made up of a number of parts, including a rotating arm (called a rotor) that constantly receives electricity from an ignition coil via brushes on the rotor's centre. The rotor then spins in time with the engine's rotation and passes its tip close to (but not on) each of the output contacts on the distributor cap, allowing the electrified rotor tip to jump across the gap between the contact and rotor.

As the rotor spins, it disrupts the current flow through the primary windings of the coil and causes the magnetic field to collapse. In the case of distributor-based ignition systems, this causes a disruption in the secondary windings as well, inducing a higher voltage to be created and transmitted to the spark plug.

A number of different types of coils are used to meet the demands of a wide variety of applications, from pencil-type ignition coils to plug-top and multi spark ignition coils. BorgWarner offers a full range of coils, including variants for fully electronic ignition processes.

Regardless of the type of ignition system, the main job of the distributor is to transform the battery's low voltage to the high voltage required to ignite the fuel-air mixture in each cylinder. It does this using the principles of magnetic induction and electromagnetism.