The purpose of the ignition system is to create a spark that will ignite the fuel mixture in cylinders of an engine. It must do this at exactly the right instant and do it at the rate of up to several 1000+ times per minute for each cylinder of your engine. If the timing of that spark is off by a small fraction of a second, the engine will run poorly or not run at all.
The ignition system sends an extremely high voltage to the spark plug in each cylinder when the piston is at the top of its compression stroke. The tip of each spark plug contains a gap that the voltage must jump across in order to reach ground. That is where the spark occurs.
The ig-system has two tasks to perform. First, it must create a voltage high enough (20,000+ volt) to arc across the gap of a spark plug, thus creating a spark strong enough to ignite the fuel for combustion. Second, it must control the timing of that the spark so it occurs at the exact right time and send it to the correct cylinder.
The ig-system is divided into two sections, the primary circuit and the secondary circuit. The low voltageprimary circuit operates at battery voltage (12 to 14.5 volts) and is responsible for generating the signal to fire the spark plug at the exact right time and sending that signal to theignition coil. The ignition coil is the component that converts the 12 volt signal into the high voltage charge. Once the voltage is stepped up, it goes to the secondary circuit which then directs the charge to the correct spark plug at the right time.