• How an Ignition Coil Works | eHow
  • Ignition System Coil - HowStuffWorks
  • Ignition System Coil - The coil provides a high-voltage current to the distributor
  • How Ignition System Works - YouTube

Fool-proof Engine Ignition Spark Tester


- In this and the following pages you will learn how the ignition coil works, how diagnose problems related to its operation, and a detailed step by step guide to replace it.

We will illustrate several vehicles from different makes and models as we get them in our shop with coil related problems.

- How does the ignition coil work?
The ignition coil is a type of electric transformer that changes low voltage electricity to high voltage electricity or current.
It works on the principles of magnetic induction. Induction occurs when a magnetic field moving across a wire induces ( creates) current flow.
The coil has two windings, or coils of wire, the primary and secondary windings.
The primary winding has several turns of heavy wire; the secondary winding has many more turns of fine wire around a soft iron core.
The difference in the number of turns between the primary and secondary is what allows the coil to increase voltage.
The ignition coil by means of electromagnetism converts the low voltage from the battery to the high voltage used to fire the spark plug.
The battery in the vehicle provides the coil primary winding with low-voltage electricity. The battery current is controlled by the ignition switch.
When the ignition switch is in the ON position, current is allowed to flow trough the ignition coil, there is often a resistor between the ignition switch between the ignition switch and the other ignition system components to prevent damage to these components due to the excessive current flow.
When a current flows through a wire, ( a conductor ), a magnetic field is built up around the conductor. There are several hundred turns of wire in the primary winding, and a strong magnetic field is produced. If the current flow is interrupted after passing through the coil, and if this interruption is quick, the magnetic field will collapse.
Since the secondary winding is made up of many turns of fine wire, there is more wire ( conductor) for the magnetic lines of force to cut. Therefore, a high voltage will be induced in the secondary winding whenever the primary current is interrupted and the magnetic field collapses.

A switching device in the ignition system turns the primary winding current on and off at the proper time. When the primary current is turned off, the magnetic field in the ignition coil collapses rapidly. This collapsing field induces a voltage in the secondary winding of the ignition coil.

Maybe you don't really need to know how an ignition coil works to test it, but it helps. I will try to keep the explanation in layman's terms for simplicity.


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