Understanding the Role of an Ignition Coil

Understanding the Role of an Ignition Coil
Vehicles could be considered a modern miracle, especially when different innovations and mechanical breakthroughs occur daily. But it's all made possible not by magic wands, but different parts that come together to make it all work– and one such part is the ignition coil. In our latest article, we'll explore the ignition coil, what it is, its construction, and its significance when powering our vehicles.

What's an ignition coil? 

The ignition coil is an integral part of the ignition system in internal combustion engines. Most ignition coils consist of two sets of wire windings. The primary winding and the secondary winding. The primary winding is composed of thicker wire and carries the low-voltage current from the car battery, while the secondary winding is made of thinner wire and generates the high-voltage output.
Its primary function is to transform the low-voltage electrical power from the battery into the high-voltage electricity needed to create sparks in the spark plugs. These sparks ignite the air-fuel mixture within the engine cylinders, initiating the combustion process that drives the engine's pistons and ultimately – powers the vehicle.  

Main vehicle engine types  

  • External combustion engine – the fuel combustion takes place outside the engine like the steam engine. 
  • Internal combustion engines – the fuel combustion process happens directly inside the engine. 


How does an ignition coil work?  

The ignition process begins when the engine's control unit sends a signal to the ignition coil to start spark formation. This signal causes an interruption in the flow of current through the primary winding. This causes a magnetic field to build up around the primary winding. The magnetic field collapses quickly when the control module abruptly cuts off the current. 
This rapid change in magnetic flux induces a high voltage in the secondary winding through electromagnetic induction. The voltage produced can reach tens of thousands of volts, and travel to the spark plugs through spark plug wires.
As the high voltage jumps the spark plug gap, it ignites the air-fuel mixture within the cylinder, starting the combustion process. This is basically what happens when we turn the key to start the engine or press a dedicated button.  


The importance of a well-functioning ignition coil  

It's important to note first that diesel engines don't have ignition coils. But essentially, the ignition coil's proper functioning is critical for the performance of internal-combustion engine vehicles.
A well-maintained ignition coil ensures that the spark plugs consistently generate strong and timely ignition, leading to efficient combustion and optimum engine power. However, as with any other mechanical part, over time, it can start to malfunction. If the ignition coil starts to fail, it can result in several issues like: 
  • Engine misfires – insufficient or weak sparks can lead to faulty combustion, resulting in engine misfires, reduced power, and increased exhaust emissions. 
  • Difficult starting – a telltale sign is when a failing ignition coil can cause difficulties in starting the engine, especially during cold weather or after the vehicle has been parked for an extended period.
  • Decreased fuel efficiency – inadequate ignition can lead to poor fuel economy, as the engine struggles to burn fuel efficiently. 
  • Catalytic converter damage – unburned fuel can damage the catalytic converter, a crucial emission control component. 


A single ignition coil vs. ignition coil pack

Modern vehicles often come with individual ignition coil packs for each cylinder (known as coil-on-plug or direct ignition system) or with coil packs for pairs of cylinders (waste spark ignition system). The former is more common in newer vehicles as it allows for more precise timing and better control over the ignition process.  
The main differences between ignition coil packs and a single ignition coil are the number of cylinders they serve, their design, and their application. Single ignition coil packs are more often found in older vehicles. In contrast, ignition coil packs offer better control, improved performance, and easier overall maintenance. This makes ignition coil packs the preferred choice in modern engines, especially those with multiple cylinders. 


How to test the ignition coil pack?

One of the popular ways to critically determine how well an ignition coil pack is functioning is to test it, of course. While professionals usually perform this, it can also be done by individuals at homes with proper experience and knowledge. This section will briefly review two test types that can help you determine whether something's wrong with your ignition coil.  

Quick performance test

Step 1: Locate the ignition coil. In most modern cars, there's an ignition pack for each cylinder. They're usually located above the engine and can be easily accessed. In most cases, they're covered, so you'll have to remove the front cover to access the ignition coil pack from a cylinder. 
Step 2: Power balance test. The first thing you should do is to test the power balance. You can do this by turning on the engine and disconnecting an individual ignition coil. If you hear a decrease in RPMs, this means that the ignition coil on that cylinder is working correctly and in full capacity. However, if you disconnect an ignition coil and don't hear any difference, the coil is malfunctioning. You may also see the check engine light come on. Continue to test all other coils the same way.  

A more detailed test

Step 1: Make sure your vehicle is turned off and access the ignition coil pack. Once you open the front hood, locate the ignition coil pack, and depending on your vehicle's make and model – remove the front lid covering the packs. 
Step 2: Remove an ignition pack. Once you can access the ignition pack, remove the side crews, which will immediately let you remove the whole pack. 
Step 3: Run a resistance or ohms reading test (with a multimeter). Locate the harness connector on the ignition coil pack you've just removed. These connectors usually have three terminals. For this test, you'll need terminals 1 and 2. The best practice to locate the correct terminals for your specific car is to either do a Google image search or consult your technician. Finally, when you touch the terminals, the multimeter should show numbers above 0. Otherwise, it would mean that the ignition coil pack is in bad shape. Do the same with all other ignition coil packs.  

Summing up 

The ignition coil's role in powering the heart of our vehicles is immense. Understanding its construction, working principle, and significance helps us to be better equipped to take care of our vehicles in a timely manner.