How To Test Ignition Coil Without A Multimeter

by David Valdez
How To Test Ignition Coil Without A Multimeter

Diagnosing ignition coil problems on a car can be tough. It’s not like the spark plugs that you can see, feel, or even hear. The car’s engine performance and the noise it generates will give you an idea about what might be going on with your car, but it won’t give you much to go on for further diagnosis. In the case of ignition coils, knowing whether there is an issue with one of them or all of them is important before you replace anything. Unless you own multiple coils and are confident that the old ones are faulty, testing each one individually is not easy. A multimeter isn’t helpful in this case because it doesn’t test voltage at high impedance. This article discusses different ways to test your car’s ignition coil without a multimeter.

How To Test Ignition Coil Without A Multimeter

Touch The Ignition Wire To The Ground

If you have a bad ignition coil, it will no longer be able to carry the full current of the spark plug. This will cause the voltage to drop in the wire and reduce the amount of current that passes through the wire when you touch the end to the ground. If the current flowing through the wire is less than a few hundred microamps, it’s a clear sign that the ignition coil is faulty and needs to be replaced. Note that this test works only for ignition coils. If you have bad spark plug wires, touching the end to the ground will show no drop in the current flow. This test isn’t very accurate, but it’s better than nothing. A 1-ohm drop in the current flow will reduce the current to about 90 microamps. A 3-ohm drop will drop it even further to about 30 microamps.

Use A Drop sensor Testing Tool

If you have a drop sensor testing tool, it can make your life much easier. A drop sensor is designed to be used just like a multimeter. It can measure current, voltage, and resistance. A drop sensor can test a single ignition coil and show you the results on its screen. If the readings show that the voltage is less than 10 volts, it means the coil is faulty. If the voltage is more than 12 volts, the coil is good. If the voltage is somewhere in between, you should take the reading as a warning sign and proceed with caution.

Hook Up A Healthy Spark Plug

If you have a bad spark plug and a healthy ignition coil, you will also have poor engine performance. The spark plug can’t spark if the ignition coil doesn’t produce enough voltage. Since the spark plug is healthy and is producing the spark you want, the fault must be in the ignition coil. A bad spark plug will have almost 12 volts. A healthy spark plug will have about 10 volts. A faulty ignition coil will have around 9 volts. This test is not as accurate as the others, but it’s enough to tell you if one of the coils is faulty. You can also use it to check the health of the rest of the ignition coils if you have more than one.

Try Starting Your Car After You Change One Coil

If you change one ignition coil, try starting your car again. If the engine is running fine and the car has no issues, you can move on with your day. If the car doesn’t start or has difficulty starting, it means that you have a faulty coil. This test works best if you change two of the coils at a time. If the car starts fine after you change both coils, it means that one of the new coils is faulty. If the car doesn’t start after you change both coils, it means that both new coils are faulty. You can also use this test if you’re not sure if one of the coils is faulty.

What Are Some Symptoms Of A Bad Ignition Coil? 

  • The vehicle will not start.
  • The engine misfires and the car runs poorly.
  • The engine overheats, causing damage to the engine and possible fire if not addressed immediately.
  • There is a burning smell from the engine compartment when starting the car or driving it, indicating that combustion is not taking place properly.
  • The engine warning light stays on and/or flashes, which means that there is a problem with one of the ignition coils or other components of the ignition system that are under manufacturer warranty for 12 months or 12,000 miles (whichever comes first).
  • Engine warning light stays on and/or flashes after 12 months or 12,000 miles (whichever comes first), which may indicate that one or more ignition coils are faulty, requiring replacement at your expense unless they are still under warranty by your vehicle’s manufacturer as indicated above in number 5 above.
  • There is a burning smell in your vehicle’s interior; this may be due to an electrical fire caused by faulty ignition coils if you have experienced any of the symptoms listed above in number 4 above, particularly if you have difficulty starting your vehicle on a regular basis as described in number 1 above, but without any flashing lights as described in number 5 above and without any noticeable misfiring while driving as described in number 2 above; this should be addressed immediately by having your vehicle towed to an authorized repair center for diagnosis and repair of the faulty ignition coils.
  • The engine does not start, even after you try to start it several times, particularly if you have experienced any of the symptoms listed above in number 1 through number 6 and without additional symptoms as described in number 7 above; this may indicate that your vehicle’s ignition system is faulty, which should be addressed immediately by having your vehicle towed to an authorized repair center for diagnosis and repair of the faulty ignition system.
  • There is a burning smell or a burning sensation when you touch any components of your vehicle’s ignition system, particularly if you have experienced any of the symptoms listed above in numbers 1 through number 8; this may indicate that there is an electrical fire caused by faulty ignition coils, which should be addressed immediately by having your vehicle towed to an authorized repair center for diagnosis and repair of the faulty ignition coils.
  • Your engine overheats or is over-revved while driving, which indicates that combustion is not taking place properly due to a problem with one or more of your vehicle’s ignition coils, causing damage to other components as well including but not limited to pistons and cylinder heads; this should be addressed immediately by having your vehicle towed to an authorized repair center for diagnosis and repair of the faulty ignition coils.

How Do You Replace An Ignition Coil? 

  1. First, you have to remove the ignition coil cover (the black plastic cover that’s over the ignition coil).
  2. Next, loosen the clamp that is holding down the ignition coil with a screwdriver or a socket wrench.
  3. Then pull up the ignition coil and remove it from its mounting bracket.
  4. Next, push down on the locking tab of your new ignition coil and insert it into its mounting bracket.
  5. Then tighten down the clamp that is holding down your new ignition coil with your screwdriver or socket wrench.
  6. Finally, take off your old ignition coil cover (the black plastic cover that’s over your new ignition coil) and put on your new one!

Conclusion

The tests discussed above are not 100% accurate and won’t tell you which coil is faulty. They will only let you know if the coil is faulty or not. This will help you decide whether to replace the coil or all the coils. If your ignition coils are faulty, you will notice poor engine performance like reduced fuel economy, poor acceleration, and reduced power. You can fix the problem by replacing the coils.

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