In order to get maximum power from the air/fuel mixture, the spark must fire at just the right moment during the compression stroke. Engineers have used several methods to control spark timing. The early systems used fully mechanical distributors. Next came hybrid distributors equipped with solid-state switches and ignition control modules (low-end computers). Then, engineers designed fully electronic automotive ignition systems. The first fully electronic ignition system was the distributor-less style (). The latest automotive ignition systems are called coil-on-plug (). In addition to improving spark timing, the newer ignition systems use redesigned ignition coils that pack a much bigger wallop to make a hotter spark. Let’s now examine each type of automotive ignition system more closely.
All automotive ignition systems have to generate a spark that’s strong enough to jump across the spark plug gap. To do that, all automotive ignition systems use an ignition coil made with two coils of wire wrapped around an iron core. The goal is to create an electromagnet by running battery voltage (12 volts) through the primary coil. When the car ignition system turns off the power, the magnetic field collapses. As it does, a secondary coil captures the collapsing magnetic field and converts it into 15,000 to 25,000 volts. There you have it. Turn power on. Turn power off and get spark. Now buckle up; here’s where things get complicated.
Distributor-based automotive ignition systems connect to the camshaft with gears. In the fully mechanical distributor, the gears spin the main distributor shaft. Inside, a set of “ignition points” rubs against a multi-sided cam on the distributor shaft. The cam opens and closes the points. That’s what starts and stops the flow of power to the ignition coil. Once the coil generates firing voltage, it travels to the top of the coil and into the top of the distributor cap. There, a rotating disc attached to the distributor shaft “distributes” the power to each of the spark plug wires.
Troubleshooting your automotive ignition system is intimidating since most electronic ignition systems have gone through major changes over the years. Though the latest versions of car ignition systems look different from their predecessors and use components with fancy-sounding names, they all work on the same basic principles. By understanding automotive ignition system basics, you can fix any of them, even the fully computerized versions. The many different variations of automotive ignition systems all boil down to three types: distributor-based, distributor-less, and coil-on-plug. Let’s look at the similarities of each automotive ignition system.