Common Lawn Mower Ignition Coil Kill Wire Issues & How To Fix Them

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The lawn mower ignition coil kill wire helps to break the circuit to the ignition coil when the machine is not in use, preventing the engine from starting. 

If the kill wire is in disrepair, the machine operator can face grave danger from a potential fire hazard or an unexpected start-up. 

This article will examine this component, its purpose, and how to diagnose and repair any potential issues. Let’s scroll down!

How Does Lawn Mower Ignition Coil Kill Wire Work?

The ignition coil kill wire is a safety feature found in many mowers. It’s a wire from the ignition coil to the kill switch on the mower’s handlebars. 

It interrupts the flow of electricity to the ignition coil. This part produces the high-voltage spark igniting the fuel in the engine’s combustion chamber. 

When the kill switch is engaged, this component stops the flow of electricity to the ignition coil, preventing the spark from being produced. It stops the engine from running.

In many emergencies, the kill switch can shut off the engine quickly. It can help prevent accidents and injuries.

What Problems May Occur In Ignition Coil Kill Wire?

What causes a lawn mower coil to go bad? The primary culprits include corrosion, loose connection, and breakage. Keep reading to learn in detail!


One of the most common issues in the mower’s ignition coil kill wire is corrosion. It can happen for various reasons, such as moisture and dirt.

When corrosion occurs, it can cause a break in the connection between the ignition coil and the kill switch. Consequently, it can prevent the engine from starting or cause it to shut down unexpectedly.

Other factors can contribute to the corrosion of this wire. For example, if you use your machine frequently, the increased wear and tear can make the wire more susceptible to environmental factors that can lead to corrosion. 

Furthermore, suppose the lawn mower is not maintained correctly, such as failing to replace the air filter regularly. In that case, it can cause a buildup of dirt and debris. And it will contribute to the corrosion of the wire.

Symptoms of a bad ignition coil on a lawn mower

Loose Connection

One of the most common issues affecting a lawn mower’s performance is a loose connection in the ignition coil kill wire. 

This problem occurs when the connection between the ignition coil and the kill switch is not properly secured. 

The consequences of such a problem can be severe, such as engine misfires or unexpected engine shutdowns. It is dangerous for the operator.

There are several reasons why a connection in the ignition coil kill wire can become loose. Vibration is among the most common causes.

As the mower operates, the vibrations cause the connection to loosen over time. This phenomenon is worse if you don’t correctly secure the connection in the first place. 

Additionally, wear and tear can cause the connection to loosen and become less effective gradually. 

Improper installation can be another reason why the connection is not secure. Consequently, it causes problems in the long run.


The third problem in the mower’s ignition coil kill wire is breakage. Excessive bending, wear, and tear, or accidental damage, cause this issue. 

In addition, breakage can occur because of exposure to harsh environmental conditions. Symptoms of a bad ignition coil on a lawn mower due to breakage include engine misfires or unexpected shutdowns. 

How To Fix The Problems In Lawn Mower Ignition Coil Kill Wire? 

If you notice any of the above symptoms, you must fix the ignition coil kill wire issue. Check our guides below!

How To Fix Corrosion

Keep the ignition coil kill wire clean and dry to prevent corrosion in this component. Moreover, it’s crucial to perform regular maintenance to prevent the buildup of dirt and debris. 

Taking these steps can help prolong the life of your machine and ensure it operates smoothly for years.

How To Fix Loose Connection

To prevent this issue, check the connection regularly and ensure it is tight and secure. You should inspect the connection periodically and tighten any loose connections as necessary. 

Proper installation of the ignition coil and kill switch can also help to prevent this issue from happening in the first place. 

By taking these simple steps, operators can ensure that their lawn mower runs smoothly and safely without any unexpected engine shutdowns or misfires.

How To Fix Breakage

It would be best to carefully handle the ignition coil kill wire and avoid excessive bending or twisting to prevent breakage.

Moreover, you must keep the lawn mower in good condition by performing regular maintenance checks. 

It includes inspecting the wire for any signs of damage, such as fraying or cracks, and replacing it as needed. 

Besides, it’s best to use high-quality ignition coils to prevent breakage. It’s also a good idea to ensure optimal performance.

What causes a lawn mower coil to go bad?

How To Test A Lawn Mower Ignition Coil?

Before diving into the testing process, look at the tools required for the job. These include:

  • A multimeter
  • A spark tester
  • Screwdriver
  • Safety glasses

Here are the steps to follow when testing a lawn mower ignition coil:

  • Disconnect the spark plug wire from the mower’s spark plug. It is to prevent any accidental engine starting during the testing process.
  • Locate the ignition coil and detach the wires connected to it. They are usually held firmly by screws, so use a screwdriver to remove them.
  • Set your multimeter to the ohms setting and connect the leads to the ignition coil’s primary terminals. The primary terminals are usually marked with a (+) and (-).
  • Check the reading on the multimeter. The ignition coil works correctly if the reading meets the manufacturer’s specifications. You must replace it if the result is outside the recommended range.
  • Reconnect the wires to the ignition coil. Then, attach the spark tester to the spark plug wire.
  • Turn on the lawn mower and check if the spark tester is flashing. If it is, the ignition coil is working correctly. If not, you must replace this piece.

Wrapping Up

The mower’s ignition coil kill wire is an essential safety feature that ensures the engine shuts off when necessary. 

You can keep your mower running safely and smoothly by understanding how this component works.

If you notice any issue with this part, consider our guides or consult an expert for immediate repair!

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