The Seasoned Wrench


Harley Davidson Ignition Coil Problems: What To Do and How

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‍Harley Davidson motorcycles are known for their powerful engines and smooth rides. However, like any mechanical device, they can develop issues over time. One of the most common problems faced by Harley Davidson owners is related to the ignition coil. But how does that affect you, and what does it mean? Should you be concerned?

This article will explore the symptoms of a bad ignition coil, how to diagnose and fix the problem, tips for preventing ignition coil issues, and provide answers to frequently asked questions.

What Are The Common Harley Davidson Ignition Coil Problems?

Ignition coils play a crucial role in the operation of your Harley Davidson. They convert the low voltage from the battery into a much higher voltage required to ignite the fuel and start the engine. So, when these coils start failing, it can lead to various issues with your motorcycle’s performance.

Here's an example of two bad ignition coils that have been removed from a Harley Davidson motorcycle.
Here, you can see that the ignition coils were removed due to some issues. In the background, you’ll see the ignition pack is still mounted on the bike.

The most common problems associated with Harley Davidson ignition coils include:

Poor fuel economy

A bad ignition coil can cause your Harley Davidson to consume more fuel than usual. This can result in decreased mileage and increased fuel costs.


If your motorcycle is backfiring more frequently, it could be due to a faulty ignition coil. When the coil fails to provide enough voltage for the spark plugs, the engine can backfire.


A failing ignition coil can cause your motorcycle to stall while you’re riding. This can be dangerous, especially when riding at high speeds.

Difficulty starting

If your Harley Davidson is struggling to start, or if it’s not starting at all, it could be due to a bad ignition coil.

Rough idling

A malfunctioning ignition coil can lead to rough idling, with your motorcycle’s engine running unevenly or hesitating when you’re at a stop.

Engine misfiring

Engine misfiring is another common symptom of a bad ignition coil. When your ignition coil is not functioning properly, your engine can misfire, causing it to run unevenly or even stall.

Here's the ignition coil removed from the bike. It's facing upside down so that we can visually inspect its electrical connections.
Before moving forward, you’ll want to perform a thorough visual inspection to rule out any quick fixes.

How To Fix and Diagnose

Fixing a bad ignition coil on your Harley Davidson involves a few steps. Here’s a basic guide on how to do it:

  1. Disconnect the battery: Before you start, make sure to disconnect the negative terminal on your battery to prevent any electrical mishaps.
  2. Locate the faulty coil: Find the coil that needs to be replaced and disconnect the cable leading to it.
  3. Remove the faulty coil: Unscrew the bolts that hold the coil in place and remove the faulty coil from the engine bay.
  4. Install the new coil: Follow the installation process to set up the new coil. Make sure the new ignition coil is compatible with your engine.
  5. Reconnect the battery: Once the new coil is installed, reconnect the battery and test the motorcycle to ensure that the problem has been resolved.
Lastly, here's the ignition coil reinstalled on the bike.
Always, as a last precaution, verify that all of the components have been correctly reinstalled on the motorcycle.

Preventing Ignition Coil Problems

Ignition coil problems can be prevented through regular maintenance and inspection of your Harley Davidson. Here are some tips to help you prevent ignition coil issues:

  1. Regular inspection: Regularly inspect your ignition coil for any signs of wear or damage. Look for cracks or signs of corrosion, as these can be indications of a failing coil.
  2. Replace old coils: Ignition coils can wear out over time, so it’s a good idea to replace them as part of your regular maintenance schedule.
  3. Use quality parts: When replacing your ignition coil, make sure to use high-quality parts that are compatible with your Harley Davidson. Cheaper, low-quality coils may not last as long and can cause further issues down the line.

What Causes These Issues?

Ignition coil problems can be caused by several factors, including:

  1. Age and wear: Like any part of your motorcycle, ignition coils can wear out over time. The constant heating and cooling can lead to cracks and other forms of damage.
  2. Heat and vibration: The heat and vibration from your motorcycle’s engine can also lead to ignition coil problems. Over time, these factors can cause the insulation on the coil to break down, leading to a short circuit.
  3. Poor maintenance: Regular maintenance is crucial for keeping your ignition coil in good condition. Neglecting to inspect and replace your coil as needed can lead to a variety of issues.

> What’s High Mileage For A Harley Davidson?
> How Long Do Harleys Last?

Has Harley Improved Their Ignition Coils?

Harley Davidson has made significant improvements to their ignition coils over the years. The introduction of electronic ignition in the early 1980s helped to increase reliability and reduce the need for maintenance. More recently, the use of Coil on Plug (COP) units, where the coils are positioned directly on top of each spark plug, has further improved performance by reducing voltage loss and improving timing.

How Frequently Do You Replace Ignition Coils?

The frequency of ignition coil replacement can vary depending on your motorcycle’s make and model, how often you ride, and the conditions in which you ride. However, as a general rule, it’s a good idea to inspect your ignition coil at least once a year and replace it every 70,000 to 100,000 miles. If you find yourself in need of a replacement, here’s a video showing you exactly how to do so:

Is an Ignition Coil The Same As A Coil Pack?

While both ignition coils and coil packs serve the same basic function – to transform the battery’s low voltage into the high voltage needed to ignite the fuel – they are not the same thing. An ignition coil is a single unit that serves all the spark plugs, while a coil pack contains multiple ignition coils, each serving one or two spark plugs. But wrapping things up, it’s important to remember that maintaining the health of your ignition coil is crucial for the performance of your Harley Davidson. By understanding the signs of a bad ignition coil and taking the necessary steps to diagnose and fix the problem, you can keep your motorcycle running smoothly and avoid costly repairs.

Related: Who Manufactures Harley Davidson Spark Plugs?


What are the symptoms of a bad Harley Davidson ignition coil?

Symptoms of a bad ignition coil can include poor fuel economy, backfiring, stalling, difficulty starting, rough idling, and engine misfiring.

How can I prevent ignition coil problems?

Regular inspection, using quality parts, and maintaining your motorcycle properly can help prevent ignition coil problems.

How often should I replace my ignition coil?

It’s a good idea to inspect your ignition coil at least once a year and replace it every 70,000 to 100,000 miles.

Can a bad ignition coil damage my motorcycle?

Yes, a bad ignition coil can cause various problems, including poor fuel economy, backfiring, stalling, difficulty starting, rough idling, and engine misfiring. If left untreated, these issues can cause further damage to your motorcycle.

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