How to Test Ignition Coil? Full Guide

The ignition coil is an indispensable part of all vehicles. High voltage is required to fire the spark plugs and the sole role of this part of the car is to provide this electricity. The optimal performance of the ignition system depends on the capability of the ignition coil.

If your vehicle is facing frequent starting issues, it's time to check the ignition coil is functioning properly or not. Before diving deep into the troubleshooting of the ignition coil, let's go through the basic principles and causes of failure of the ignition system.

ignition coil repair

How does an Ignition Coil Work?

The basic principle of an ignition coil is similar to a transformer. It creates high voltage from a low voltage input. Modern vehicles use ignition coils with integrated electronic control units and they are equipped with a transistor ignition. These electronic parts can slowly degrade with extended usage and it will adversely affect the performance of your vehicle.

The electrical resistance of the ignition coils will increase over time and that will lead to less efficient power output. The vehicle will start showing abnormal symptoms when the ignition coil's performance diminishes.The main symptoms of a faulty ignition coil are:

  • The engine does not start.
  • Vehicle misfires while starting.
  • Acceleration issues and decrease in vehicle power.
  • A decrease in fuel efficiency.
  • Engine warning lamp on cluster meter.

If you experience these symptoms frequently, we recommend checking the ignition coil and finding whether it is damaged for sure or not. In fact, in this article, we will guide you on how to test the ignition coil of your vehicle and also introduce you to the necessary tools required to execute the test. Without further ado let's check how we can test the ignition coil without visiting a professional car service.

How to test ignition coil

Things to Keep in Mind Before Testing Ignition Coil

Ignition coil testing tips

The ignition system is a sensitive part of your vehicle and we will never recommend pulling off a plug wire or the coil's high voltage output wire to test for a spark without taking any safety measures. There is a risk of severe electric shock and you may damage the ignition coil completely.

Go through the instructions carefully and follow the recommended safety measures to ensure safe testing. Considering that working around the ignition system of your car can get dangerous at times, we strongly recommend you get the following safety wears before starting the test.

  1. Safety glasses: Eye protection is a priority. Get a pair a safety glasses to make sure you don't end up blind testing your car. Here is a great option.
  2. Mechanic Gloves: Protect your hands and body from possible electric shock and high voltage. Here are some of the best mechanic gloves available on Amazon.
  3. Use a good quality toolset to remove the ignition coil from the vehicle ignition system. This basic toolkit is a must-have for your garage.

Speaking of necessary things that you should have for your car, here you can find the best off-road GPS that every car lover should have.

How to Test Ignition Coil?

testing ignition coil

Once you get all the safety wears ready, let's get into the real business and learn how to test the ignition coil of your car. First of all, park your car on a flat surface, preferably in your garage. Turn your car off and allow it to cool off before attempting any of the below steps.Remember that you can find the ignition coil often on the right side of the engine.

If you can't, check the user manual of your vehicle (this website is a great resource for car user manuals) for the exact location of the ignition coil. Once you find it, look carefully for any possible cracks, burns, melting, or leakage in coils. If the damage is major, you should buy a new one and go for a direct replacement.

If you can't find any visual damages in the coil, then we can go to the next step. If you also have an issue with your cotter pin, this blog post might be helpful for you.

Test a Test With Multimeter


You can check the ohm resistance of the ignition coil with a multimeter. All you need is a good quality multimeter that gives an accurate reading. Our all-time favorite is this one:After you got your multimeter, check the repair manual of your vehicle for the expected resistance reading of the ignition coils.

Get your safety gloves on and connect the multimeter’s positive and negative leads to the corresponding terminals in order to test the primary and secondary windings.Check the readings on the multimeter and make sure it matches the specified resistance readings mentioned in the user manual of your vehicle.

If the resistance readings fail to meet the required level, you need to replace the ignition coil. Before getting to any conclusion, re-check the readings and make sure you followed all the instructions in the manual.

Conducting Spark Test

spark test

This is the most effective way to test the ignition system for possible faults. The spark test is complicated but using the right tools will make things easy for you. One of those tools is the ignition spark tester. This tool will make the testing hassle-free. The ignition spark tester has a spark plug cap that fits on to an individual spark cylinder so that you can check each spark plug or cylinder individually.

This ignition spark tester on Amazon seems to be very popular: Before using this ignition spark tester, make sure to turn the engine off and disconnect the ignition coil from the spark plug. Carefully connect one end of the spark tester to the top of the spark plug, and connect the other end to the coil output.

Once the spark tester is connected properly, start the engine. The spark tester flash will determine the condition of the ignition coil, if the light on the spark tester flashes, the coil is generating the required firing voltage. If there is no flash in the tester it means either a faulty ignition coil or major issues in the coil control circuit. You can learn how to fix the ignition coil of your car in this video:

Final Thoughts

The ignition coil testing is a process even beginners can try and we believe the above steps will help you throughout the process. After making the test, if you find it is not functioning properly, we recommend a complete replacement. If after this guide, you still don't feel sure whether you can conduct the test yourself then perhaps you should go ahead and take your car to a professional car service.

Remember, safety always comes first! Therefore, if you don't feel safe doing this process yourself, you should definitely visit mechanics. In case, you decide to do it yourself then make sure to use protection wear!

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