Regardless of whether it's an automobile engine or the engine of a lawn mower, 'ignition coil' is undoubtedly the most important component of the same. It is this component of the ignition system that generates the enormous amount of power which is necessary to spark the spark plug. But how does an ignition coil generate such enormous amount of power? In order to understand that, you need to be well-versed with its working mechanism.
What is an Ignition Coil and How Does it Work?
In an internal combustion engine, 'ignition' refers to the process wherein a spark produced by the spark plug triggers an explosion and ignites the air-fuel mixture required to power the engine. The ignition system consists of several components, namely ignition coil, spark plug, distributor, rotor, etc. Each of these are assigned a specific function in the engine's overall working mechanism. While the spark plug creates a spark required to trigger the explosion of fuel-air mixture, the distributor distributes this spark to the appropriate spark plug.
The power that the 12-volt battery used in the machine tends to produce is insufficient to trigger the spark necessary to facilitate explosion, which is where the 'ignition coil' comes into the picture. It converts the battery's 12-volt power into 40 kV power required to create the spark. In other words, it is an induction coil, which converts the relatively weak power from the battery to enormous power―amounting to 40 kV―that is required to produce the spark which ignites the air-fuel mixture in the ignition system.
The current from the battery begins building up when the contact breaker closes, and continues until it reaches its full capacity. Once it reaches its full capacity, the contact breaker opens and the high voltage spark is produced. If the ignition coil is not there, the 12v DC battery on board the vehicle is of no use, as such little amount of power is not sufficient for creating the spark that's required to produce the explosion. While some of these coils resort to resistor to reduce the voltage, others rely on a resistor wire or an external resistor to facilitate the same.
Basically, the ignition coil is made up of two coils of wire―placed one on the top of other. These coils are also referred to as windings, with the first coil being referred to as the 'primary coil', while the second coil, which is wrapped around the primary coil, being referred to as the 'secondary coil'. The number of turns in secondary coil is in multiples of the number of turns in its primary counterpart. The current flows from the battery through the primary coil, wherein it is collected together to produce the required spark, which is eventually sent to the distributor by the secondary coil.
In order to make sure that the tremendous amount of heat generated in this process doesn't harm the coil, it is filled with oil which acts as its coolant. While some engine models are equipped with a single ignition coil, others have one for each spark plug. In models with single spark plug, a distributor is used to distribute the spark to the appropriate spark plug.
Of the various ignition problems that you are likely to face, weak spark and coil not firing are the ones that are attributed to the ignition coil. In order to diagnose these problems, you can either resort to the spark plug test or the bench test. That will help you determine whether you need to replace it.