How to Know If Harley Ignition Coil Is Bad


Often issues from the engine of Harley Davidson could be indications that the ignition coil of your bike is bad. Even though there are differences in models like Street, Sportster, Dyna, Softail, V-Rod, but the signs of bad ignition coil remain the same across all models of Harley and can easily be identified.

Here we discuss the signs of a faulty ignition coil specifically in Harley Davidson motorcycles. Double-check every faulty or unusual thing your bike is doing and take experts’ advice if needed.

Signs of a Faulty Coil

These are the signs that indicate that your bike has a faulty coil that needs replacement or repair:

Bad Mileage

When your Harley’s ignition goes bad or needs to be repaired, its efficiency is lost and your bike will be using more fuel than the usual amount. If you notice that you are filling the tank more than the normal amount, checking the ignition coil is a good idea!

Issues with starting the engine

Cranking noises and issues with starting the engine are two of the common signs that the ignition coil is bad. If you have a Harley single fire coil, you will be hearing cranking noises but there won’t be any sparks.

Stalling of the bike

Another symptom that indicates a faulty ignition coil is if your bike is stalling. This stalling usually results from unwanted sparks that are sent to plugs. These sparks occur from the faulty coil and that is why your bike starts to stall or does not start anymore.

Bad idling

Along with engine jerking, you may see rough idling from your bike due to a faulty ignition coil. Compare the idling speed of your bike from before and see if the speeding up is the same or not. You may feel that the bike is lacking power while starting up.

Misfiring of the engine

When the engine misfires from your Harley Davidson, chances are the coil has gone bad instead of the engine. It can be identified with loud noises from the engine when you start it. Moreover, further indications can be made when your engine becomes unstable while you ride your bike at a high speed. Usually, the engine will jerk, spit and vibrate unusually.

Code P0351

You can troubleshoot the issue of a faulty coil by using a diagnostic tool for scanning. When you scan, the code ‘P0351’ will show up. This code is an indicator of circuit issues that can be the result of a bad Harley ignition coil.

Harley Davidson Ignition Module Testing

If you want to make sure that the issue you are facing with your motorcycle is the direct result of its ignition coil, follow these steps:

  • Make sure your bike is off and it is cool.
  • Use an SAE wrench to take off the plug wires from the ignition coil.
  • Now, you need to check the resistance of the coil using an ohmmeter. Connect it to two terminals (small) and check if the resistance is within 2.5-3.1 ohms.
  • Now you have to do the same thing for the two big terminals. This time the resistance should be within 10,000-12,500 ohms.
  • If the resistance is not on the range mentioned, your coil is faulty.

Replacing the ignition coil

  • Disconnect the cable that connects to the coil and the battery’s negative terminal.
  • Remove the coil entirely by unscrewing the bolts around it.
  • Screw the new coil in the same place.
  • Connect the cables accordingly.

Note that, you must purchase the new coil according to the model of Harvey you have. Make sure the bike is completely cooled off before doing this. If you are unsure, take help from a professional.

Final Note

Usually, many people tend to think their Harley’s engine has gone bad when it is just an issue with the coil. Checking it yourself and diagnosing the problem with simple tools will help you save money and not get scammed by repairers telling you that the engine’s at fault.

Always keep the right tools like wrench, screwdrivers, ohmmeter, etc. if you work on your bike personally for repairs and replacements. Being handy with tools and understanding the basics of the bike will allow you to solve most of the common problems.

Alston Seymour

A Harley-Davidson Motor Company certified Master Technician and avid biker, I love to write about everything and anything related to biking.

Click Here to Leave a Comment Below 2 comments
Johnny Cope - April 2, 2023

Bought a Dyna S kit 7/24/2022 from ATV Galaxy on Ebay for 1976 Honda GL1000. One coil, 30ohm, has a bad port. Contacted ATV Galaxy and was told to contact Dynatek. What do I need to do to get the coil replaced? Thank you, Johnny. Having problems contacting your support.

    Alston Seymour - June 4, 2023

    To get the faulty coil in your Dyna S kit replaced, follow these steps:

    Contact Dynatek: Since ATV Galaxy directed you to contact Dynatek, reach out to Dynatek directly regarding the issue. You can find their contact information on their website or through an online search.

    Provide necessary details: When contacting Dynatek, explain that you purchased the Dyna S kit from ATV Galaxy on eBay for your 1976 Honda GL1000. Clearly mention that one of the coils in the kit is defective and needs to be replaced.

    Share the problem: Describe the specific issue with the faulty coil, mentioning that it has a bad port. Provide any additional relevant information or symptoms you have noticed.

    Request a replacement: Ask Dynatek for a replacement coil. They should be able to assist you with the warranty process or guide you on the steps to obtain a replacement.

    Provide proof of purchase: Be prepared to provide proof of purchase for the Dyna S kit. This can include your receipt or any other documentation that verifies your purchase from ATV Galaxy on eBay.

    Follow Dynatek’s instructions: Dynatek may require you to return the faulty coil for inspection or provide further details. Follow their instructions carefully to ensure a smooth resolution to your issue.

    By following these steps and communicating with Dynatek regarding the defective coil, you should be able to initiate the process of getting it replaced. Remember to keep any relevant documentation and maintain open communication with Dynatek to resolve the issue effectively.


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