Often overlooked, the ignition coil is actually one of the most important components in your car. It’s responsible for producing the high voltage that creates the spark that ignites your vehicle’s fuel and helps your engine run properly. Without the ignition coil, your engine would likely stall or not start at all. But what exactly is an ignition coil and how does it work?

An ignition coil is an electrical transformer that steps up voltage from the battery to a much higher level. It uses a pair of separate wires, both coiled around an iron core and insulated by the coil itself. One wire, called the primary, is coiled thousands of times more tightly than the other, called the secondary. The combination of these two insulated wires forms an electromagnet and when the ignition system switches on current flow, it triggers the primary winding to generate magnetic energy. Then, when the ignition system shuts off the current, this magnetic field collapses across the gap of the spark plug and induces a voltage into the secondary winding. This voltage is then used by the spark plug to fire across the air/fuel mixture and create the explosion needed for your car to start.

A bad ignition coil can cause your car to experience a number of issues, from difficulty starting to poor fuel economy. If you’ve been experiencing any of these symptoms, it may be time to replace your ignition coil.

In older cars with a distributor, an ignition coil will look like a small metal cylinder (or sometimes, as on older Volkswagen models, a canister-type ignition coil) with wires sprouting from it. These wires connect the coil to battery voltage, to contact points within a mechanical distributor called the distributor cap and to a central high-tension lead that goes to the centre of the coil. A rotating disc on the distributor shaft then 'distributes' this high-voltage spark to each of your car’s spark plugs via individual spark plug wires.

Ignition coils in newer cars are typically found directly atop your spark plug, rather than in the distributor cap. This is known as a 'coil on plug' or COP ignition system. These systems require fewer parts, are easier to maintain and service, and reduce the chances of contamination by oil or other fluids.

Replacing a stock ignition coil is relatively simple and can be done at home, although you’ll probably need a few tools and some basic technical knowledge. If you’d prefer to have a professional do the job, most auto shops offer a wide selection of replacement ignition coils and will be happy to assist with your car’s maintenance needs. Using the right ignition coil ensures that the high-voltage spark necessary to ignite your engine is generated and delivered reliably to each of your spark plugs.