How to Troubleshoot a Spark Plug Ignition Coil

How to Troubleshoot a Spark Plug Ignition Coil

Machine lost spark, easiest thing to check is the spark plug coil

A spark plug coil, also known as an ignition coil, is a vital component of a vehicle's ignition system. It plays a crucial role in generating the high voltage required to create a spark in the spark plugs, which ignites the air-fuel mixture in the engine's combustion chamber. When a spark plug coil malfunctions, it can lead to various issues, including engine misfires, decreased fuel efficiency, and even potential engine damage. In this comprehensive guide, we will walk you through the process of troubleshooting a spark plug coil.

Step 1: Check for Warning Signs

Before diving into troubleshooting, it's important to be aware of the warning signs that may indicate a faulty spark plug coil. Some common symptoms include:

  • Engine misfires or hesitation during acceleration
  • Poor fuel efficiency
  • Difficulty starting the engine
  • Check Engine Light (CEL) illuminated on the dashboard

If you experience any of these symptoms, it is recommended to inspect your spark plug coil.

Step 2: Inspect the Spark Plug Coil

Start by locating the spark plug coil on your powersports vehicle . Depending on your vehicle, it is usually situated on top of each spark plug or grouped together in a coil pack. Inspect the coil for any visible signs of damage, such as cracks, corrosion, or burn marks. These can be indicative of a faulty coil that needs to be replaced. Additionally, check the coil's electrical connector for any loose or damaged wires. If you notice any of these issues, it is likely that the coil is causing the problem.

Step 3: Test the Resistance

Testing the resistance of the spark plug coil can help determine its condition. Using a digital multimeter, set the multimeter to the resistance (ohms) setting. Remove the coil's electrical connector and connect the multimeter probes to the positive and negative terminals of the coil. Compare the resistance reading with the specifications provided by the manufacturer. If the resistance is outside the acceptable range, the coil is likely faulty and should be replaced.

Step 4: Check for Voltage

To check for voltage, reconnect the electrical connector to the coil. Set the multimeter to the voltage setting. Connect the multimeter's positive probe to the coil's positive terminal and the negative probe to a good ground. Have someone crank the engine while you observe the multimeter. You should see a voltage reading. If there is no voltage or if it's significantly lower than the manufacturer's specifications, the coil may be faulty.

Step 5: Swap Coils

If your vehicle has multiple spark plug coils, you can try swapping the suspected faulty coil with a known good one. Clear the error codes using an OBD-II scanner and test the vehicle. If the symptoms move to the cylinder controlled by the swapped coil, it indicates that the original coil is indeed faulty.

Step 6: Consult a Professional

If you have followed the previous steps and are still unsure about the condition of your spark plug coil, it is recommended to consult a professional mechanic. They have specialized diagnostic tools and expertise to accurately diagnose and repair ignition system issues.


Troubleshooting a spark plug coil is an essential skill for any vehicle owner. By following the steps outlined in this article, you can determine whether a spark plug coil is faulty and take appropriate action. Regular maintenance and timely replacement of faulty components will ensure optimal engine performance and prolong the lifespan of your vehicle. Remember, if you are uncertain or uncomfortable performing these troubleshooting steps yourself, it's always best to seek professional assistance.

Additional Tips

Here are some additional tips to keep in mind:

  • Inspect and replace spark plug wires if necessary, as damaged wires can affect the performance of the spark plug coil.
  • Ensure proper grounding of the spark plug coil and its electrical connections.
  • Consider replacing all spark plug coils simultaneously if one coil is found to be faulty, as the others may also be nearing the end of their lifespan.
  • Regularly clean the spark plug coil and its surrounding area to prevent the accumulation of dirt and debris.
  • Refer to your vehicle's owner manual or consult a professional for specific instructions and recommended maintenance intervals.
Back to blog