Ignition Coil

Learning Objectives

By the end of this lesson, students will be able to:

Explain the function of an ignition switch in an automotive ignition system.
Identify and differentiate the types of ignition switches used in vehicles.
Understand the role of each ignition switch position and its impact on vehicle operation.

What Is An Ignition Coil?

An ignition coil is a vital component of a vehicle's ignition system. It is responsible for converting the low voltage from the battery into the high voltage needed to produce sparks at the spark plugs. The ignition coil acts as a transformer, utilizing electromagnetic induction to generate the high voltage required for efficient combustion in the engine.

Functioning of an Ignition Coil

The ignition system is a crucial part of a vehicle's engine, initiating combustion. It comprises several components, including the ignition coil, spark plugs, distributor (in older systems), and control module.
The ignition coil plays a pivotal role in the ignition system by generating the high voltage required to produce sparks at the spark plugs. It is typically connected to the vehicle's battery and ignition switch. When the ignition switch is turned on, a low-voltage current flows through the primary winding of the ignition coil.
The ignition coil transforms the low voltage from the battery into a high voltage output through electromagnetic induction. The primary winding creates a magnetic field when the current flows through it. This magnetic field collapses rapidly when the current is interrupted, inducing a high voltage in the coil's secondary winding. The high voltage output from the secondary winding is sent to the distributor (or directly to the spark plugs in newer systems) to create sparks.
The transformation of low voltage to high voltage through induction in the ignition coil is a crucial step in the ignition process. It ensures that the spark plugs receive a high-voltage pulse, which ionizes the air-fuel mixture in the engine cylinders, creating a spark that ignites the mixture and initiates combustion. The ignition coil's ability to generate high-voltage sparks is vital for efficient engine operation and power delivery.

Introduction to the Ignition Switch

The ignition switch is a critical component in an automobile’s ignition system. It is the mechanism used to power the vehicle's electrical systems and engage the starter motor to crank the engine. Typically, the ignition switch is operated using a key, but modern vehicles may use push-button systems integrated with electronic key fobs.

Main functions of an ignition switch include:

Providing power to the ignition system and fuel system.
Enabling accessories like the radio and lights.
Starting the engine.
Locking the steering column (in some designs).

Ignition Switch Positions

A traditional ignition switch has the following positions:

LOCK (OFF): The steering wheel may be locked, and no electrical circuits are active.
ACC (Accessory): Allows operation of electrical accessories without turning on the engine.
ON (RUN): Powers all vehicle electronics and the engine control system.
START: Activates the starter motor to crank the engine. Once the engine starts, it returns to the ON position.

Ignition Coil Parts

The main parts of an ignition coil include two separate windings or coils known as the primary winding and secondary winding, a high voltage cable connecting the ignition coil to the other ignition system parts, an insulator which serves as a barrier between both windings and an iron core which concentrates the magnetic field created by the electrical current passing through the coils.

DIFFERENT TYPES OF IGNITION COIL

Stick Coil:
A compact, stick-shaped coil designed for ease of installation and potentially higher performance.

Distributor Coil:
Part of a distributor system, which uses a rotating shaft to deliver high-voltage current to the spark plugs in the correct order. While traditional mechanical distributors are being replaced with electronic ones, the distributor coil remains a key component.

Ignition Coil Block:
A distributor-less ignition system with multiple coils in a single unit, providing voltage to different spark plugs at the same time.

Coil-on-Plug (COP):
Each spark plug has its own dedicated coil, delivering high voltage directly, often resulting in improved performance and efficiency.

Block Coils (also known as multi-outlet coils):
Combine multiple coils into a single unit, providing voltage to different spark plugs. These can be single-spark or double-spark, and may or may not have an integrated output stage.

Pencil Coils (also known as coil-on-plug):
Designed to be plugged directly into the spark plug, often used in modern vehicles with fully electronic ignition systems.

Summary

The ignition coil is a transformer that plays a vital role in delivering the necessary high voltage to spark plugs. Various types of ignition coils—such as conventional, coil packs, COP, and CNP—are used based on vehicle design and performance needs. Understanding the differences in design and function is essential for diagnostics, repair, and performance tuning.

References

Erjavec, J., & Thompson, R. (2020). Automotive technology: A systems approach (6th ed.). Cengage Learning.

Halderman, J. D. (2019). Automotive electricity and electronics (6th ed.). Pearson Education.

Bosch Automotive Handbook (10th ed.). (2018). Robert Bosch GmbH.

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