An ignition coil is important for the car’s engine as it relays the battery power to the spark plugs for you to start and keep the engine running. That is why when one of the ignition coils does not work, you need to replace it or you end up with an engine that misfires all the time.
You will come across most cars having the same number of ignition coils based on the number of cylinders. So, it is one coil per cylinder. If you have a V6, it could mean 6 coils for such an engine. The same applies to the 3, 4, and 8-cylinder engines.
Sometimes the engine could have fewer coils. This is largely dependent on the manufacturer’s design of the engine, but the option of one coil per cylinder is the most common.
How an Ignition System Works
The ignition coil has two coils of wires that are wrapped around an iron core key for ensuring there is a strong spark key for igniting the fuel and air mixture by the spark plug. So, the work of the ignition coil is to create enough spark that can jump across the gap in the sparkplug head.
Whenever power is passed through the ignition coil, it creates an electromagnet in the primary coil. This electromagnetic field collapses once the power is turned off. Take note that a secondary coil captures the electromagnetic field and converts it into a 25,000-volt field.
The spark must be fired at the right time to generate maximum power from the fuel and air mixture. That is why engineers design methods for controlling when the spark happens through exciting the ignition coils.
This is why you can come across different types of ignition systems that work differently to achieve the same thing. Newer cars now have improved systems that would generally make it easier to have a good and running car that is also efficient in terms of fuel used and power generated.
This video talks more about how ignition coils work
Types of Ignition Coil Systems
There are a number of ignition coil systems on the market right now. We look at some of the most used in many cars and see how they work.
- Distributor ignition system
This is one of the oldest systems but still works great. In this type of system, the mechanical distributor ignition system is connected to the camshaft through some gears. This system has ignition points that work like mechanical switches which interrupt the flow of current. The result is that they can now offer the right timing for firing the sparkplug.
As much as it is a good system, it commonly had issues such as the ignition points breaking down thus changing the spark timing. This would mean the engine does not run as efficiently as it is supposed to.
You would have to consider replacing the ignition points a lot sooner depending on how often the car is used.
- Distributor-less ignition system
This was a newer technology from the distributor system. Here, the timing was based on two sensors namely, the crankshaft position sensor and camshaft position sensor. A computer has to monitor these two sensors and only allow for spark at the right timing.
In this system, each coil would have a stronger electromagnetic field sometimes reaching 30,000 volts. This meant that the newer cars with the system would perform better in terms of fuel efficiency.
- Coil-on-plug ignition system
The coil-on-plug system works similarly to the distributor-less system, only that each coil, in this case, is only used for one cylinder. Another difference is that you get twice the power from the magnetic field. So, expect the system to generate as much as 50,000 volts or more. This means stronger sparks.
In this system, the coils are mounted directly on top of the spark plug. This would help in eliminating the need for spark plug cables. Also, there is less amperage loss since the plugs are connected directly to the coils.
Here is a video on how the coil-on-plug system works
Common Ignition Problems and Their Solutions
Sometimes you may come across problems with ignition coils. It is only when you know how to identify such problems that you can work on them. Let us see the most common signs that your ignition coils have problems.
- A stalling or misfiring engine
When a coil is faulty, it means that the spark timing will also be off. The result is that now you have a misfiring engine. If the coil has no spark at all, the engine ends up stalling. You may notice this mostly when the engine is idling. The common sign is that the engine vibrates a lot or the car tends to jerk too.
- The car won’t start
A car also won’t start if several coils are faulty. This is even when the battery is fully charged, but when you turn the key, there is nothing. This means that the spark plugs are not receiving any power thus the reason your engine will not fire up.
- Low gas mileage
One thing about gas mileage is that you can notice it quickly. The idea is that when the engine is not burning enough fuel, the computer would keep sending signals for more fuel. This means that the car runs rich. This is mostly because the coils are not working as they should.
- The check engine light comes on
Faulty ignition coils could also be the reason you see the check engine light on the dash. Of course, there could be many other reasons, but it does not hurt you to check if the coils are working correctly. Here, you will need to use a scanner to help see the reason why the check engine light is on. It will tell you if there is a problem with your coils.
How do you avoid having faulty ignition coils?
Make sure you inspect the ignition coils regularly. This means whenever you do your car’s overall service check, do not forget to look at the coils too.
Do cars have many ignition coils?
For most configurations, it would be one coil per cylinder. However, some cars are different, so look at the manufacturer’s guide for more details.
What is the cost of replacing ignition coils if they fail?
The average price for replacing the coils is $160 to $200 including labor. It would also depend on the car’s make and model.