Ignition Coil Test: The Ultimate Guide to Diagnosing & Testing your Ignition Coils

Date Posted: 21 May 2020 

Ignition Coil Test: The Ultimate Guide to Diagnosing & Testing your Ignition Coils main image Ignition Coil Test: The Ultimate Guide to Diagnosing & Testing your Ignition Coils image
Do you suspect that there’s something wrong with your ignition coil? If yes, then you should test it with a multimeter. Driving over a longer distance with a misfiring engine can damage the engine and break the bank.

A weak or damaged ignition coil can cause engine backfires, stalling, difficulty starting the engine, and even lower fuel economy. And if you have a broken one, it will prevent your vehicle from running at all.

If you think you are having an ignition coil issue, whether it's the coil, ignition lead, or the ignition coil pack, you’ll want to test your coils to determine which one is having a problem. Follow this guide to help you diagnose and test your ignition coils.

How an Ignition Coil Works?

Ignition coils are known as compact electrical transformers that take energy from a battery (usually 12-v) and convert it to a high voltage to create a spark. This energy travels through the distributor to spark the plugs, igniting the fuel. The spark plugs in a car have their own individual coil. Each coil is either physically connected to spark plug through a wire or sits on top of the spark plug without using wires.

For the spark plug to ignite the fuel, it needs about 15,000 to 20,000 volts of electricity to form an electric spark. If your ignition coils are weak or damaged, it will result in weak fuel or engine misfires. It’s important to note that a troublesome ignition coil can also be related to a low voltage or an abnormally high voltage battery. If this is the case, upgrading to a new battery can help many issues go away.

Signs Your Ignition Coil Needs Replacement

It may take a lot of work to test your ignition coils, that’s why you’re going to need to do your initial diagnosis first. In this way, you will save yourself some time if you find that the signs don’t match up. Here are symptoms that you need an ignition coil replacement:

  • Backfiring: It’s hard not to notice when your car backfires. The “check engine” light on the dashboard usually turns on and sometimes accompanied by a smell of gasoline.
  • Stalling: If your car abruptly stops and starts, it can really be frustrating. If this happens, you might want to check your coils.
  • Lower fuel economy: Does your vehicle consume more gas than usual? You may have one or more faulty ignition coils.
  • Difficulty starting the engine: Having a hard time starting the engine? If you’ve ruled out your battery, then it’s time to check your ignition coils.

If your vehicle shows one or more of these signs, you might want to do an ignition coil test and check which coil needs replacement.

How to Test Ignition Ignition Coils

  1. Before doing any tests, make sure that your vehicle has cooled down and your emergency brake is on. Open the food and disconnect the negative battery cable.
  2. Locate your ignition coils. They can be found near or on the engine. Disconnect the mounting bolts holding the ignition coils to remove each coil.

  3. Each ignition coil consists of two separate coils: the primary winding and the secondary winding. Both coils are wrapped around each other. The primary winding is made of heavy wire and receives energy from the battery. You should test this part first.

  4. Check the owner’s manual to find out what the correct resistance reading should be.

  5. Connect the multimeter to the corresponding terminals on the ignition coil.

  6. Compare the reading to the resistance specification for the primary winding. You will be needing to replace the ignition coil if the reading falls outside the normal resistance range. If the reading looks okay, move to check the secondary winding

  7. The secondary winding is made of thin wires that coil many times. It receives energy from the primary one, which it then sends along to the vehicle’s spark plugs. Follow these steps:

  8. Connect the multimeter’s leads to the positive terminal and the centre pole.

  9. Compare the reading to the resistance specifications for the secondary winding. You will need to replace your coils if it falls below the normal range.

  10. If you have more than one ignition coil, be sure to test each one. Replacement coils should be the same as the original ones. Reinstall or replace them, depending on the result of the test.

Frequently Asked Questions

How long does an ignition coil last?

The ignition coil of your car should last for 100,000 miles or more. While some can become damaged prematurely

How much does it cost to replace the ignition coil?

It depends on your car make and model but you can check out the Ignition coil price

Can you drive with a bad ignition coil?

You should not drive your vehicle when you have a bad ignition coil. Yes, you’ll be able to drive the car but it will only cost further damage and might cause bad things to happen.

Should I replace all ignition coils at once?

It depends. If you think it’s due to replace all your ignition coils even if just one of them is bad, then you can. If you just replaced all and one coil goes bad, you can just replace one.

My car keeps on misfiring what can I do?

If you or your mechanic is certain that misfiring is the problem than the question is, have you bought your spare parts from a reputable wholesaler like Machter Autoparts? If not, it’s possible you became a victim of counterfeit products. It’s not that common but it’s possible that you have replaced Ignition coils or spark plugs that are counterfeit. Counterfeit Ignition coils or spark plugs can create huge damage to your motor since they do not meet impedance, resistance or temperature specification. In such case confirm and investigate if you used quality aftermarket products from a reputable source.

Need ignition coils replacement?  Here at Machter Auto, we offer ignition coils that are perfect for every car make and model. Shop from a wide range of auto parts online with the following benefits:

  • High-quality auto parts
  • Over 15,000 auto products
  • One-stop solution to your auto need>
  • Worldwide distribution of auto products
  • Specialist expertise and support

Get in touch with one of our friendly experts today to help you find the best parts for your vehicle! Call the team on  (02) 7801 4933