Step-by-Step: How to Check Lawn Mower Ignition Coil and Boost Your Mower’s Power!

Is your lawn mower refusing to roar to life? A faulty ignition coil is a common culprit behind a frustratingly silent lawn. This critical component delivers the high voltage needed to ignite the spark plug, and when it’s on the fritz, your mower won’t even cough.

This guide will walk you through the process of how to check lawn mower ignition coil and equip you with the knowledge to diagnose and potentially fix this common issue.

Understanding the Ignition Coil

The ignition coil is a vital part of your lawn mower‘s engine, acting as the bridge between the low voltage electrical system and the high voltage required to fire the spark plug. It’s essentially a transformer that steps up the battery’s 12 volts to thousands of volts.

Here’s how it works:

1. Power Supply: The ignition coil receives power from the battery through the ignition switch.
2. Magnetic Field: When the ignition switch is turned on, current flows through the coil’s primary winding, creating a magnetic field.
3. Voltage Boost: When the points or electronic ignition system open, the magnetic field collapses, inducing a high voltage pulse in the secondary winding.
4. Spark Plug Ignition: This high voltage pulse travels to the spark plug, creating a spark that ignites the air-fuel mixture in the combustion chamber.

Identifying Symptoms of a Faulty Ignition Coil

Before you dive into testing, it’s crucial to identify the symptoms of a faulty ignition coil. Some common signs include:

• No Spark: The most obvious sign is a complete lack of spark at the spark plug.
• Engine Cranks But Doesn’t Start: The engine may crank but fail to fire up, indicating a problem with ignition.
• Intermittent Starting: The engine might start occasionally but then stall, pointing towards an inconsistent spark.
• Engine Misfiring: A faulty ignition coil can lead to misfires, causing the engine to run roughly.

Tools You’ll Need

Before you begin, gather the following tools:

• Multimeter: This essential tool measures voltage and resistance, allowing you to test the ignition coil.
• Spark Plug Wrench: Used to remove and install the spark plug.
• Wire Connectors: For temporarily connecting wires to the ignition coil.
• Safety Glasses: Protect your eyes from potential sparks.
• Gloves: Protect your hands from potential burns or cuts.

Step-by-Step Guide to Checking the Ignition Coil

Now, let’s walk through the process of checking your lawn mower‘s ignition coil.

Step 1: Disconnect the Spark Plug Wire

Using the spark plug wrench, remove the spark plug wire from the spark plug. Make sure the wire is disconnected to avoid any accidental shocks.

Step 2: Test for Spark

With the spark plug wire disconnected, hold the spark plug wire end near a grounded metal surface (like the engine block). Turn the engine over briefly. You should see a bright blue spark jumping from the wire end to the metal surface.

If you see a spark: The ignition coil is likely functioning properly. The issue might lie elsewhere, such as a faulty spark plug or wiring.

If you don’t see a spark: Proceed to the next step.

Step 3: Check the Ignition Coil for Continuity

Use your multimeter to test the continuity of the ignition coil‘s primary and secondary windings.

• Primary Winding: Set your multimeter to the resistance setting (usually “ohms”). Connect the multimeter probes to the terminals on the primary winding of the coil. You should get a reading of a few ohms. If the reading is infinite or very high, the primary winding is open and needs replacement.
• Secondary Winding: Repeat the process, connecting the probes to the terminals on the secondary winding. The reading should be much higher, typically in the kilohms range. An infinite or very high reading indicates a problem with the secondary winding.

Step 4: Check the Ignition Coil for Ground

Ensure that the ignition coil has a good ground connection. Connect one probe of your multimeter to the coil’s ground terminal and the other probe to a known good ground on the engine. You should get a reading of zero ohms. If the reading is infinite or very high, the ground connection is faulty and needs attention.

Step 5: Test the Ignition Coil for Voltage

With the engine running, connect the positive probe of your multimeter to the positive terminal of the ignition coil and the negative probe to a good ground. You should get a reading close to the battery voltage (usually around 12 volts). If the reading is significantly lower, it could indicate a problem with the coil’s internal wiring or a loose connection.

Replacing the Ignition Coil

If your tests reveal a faulty ignition coil, it’s time to replace it. Here’s a general guide:

1. Locate the Ignition Coil: It’s usually mounted near the spark plug and connected to the wiring harness.
2. Disconnect the Wires: Disconnect the wires leading to the ignition coil, taking note of their positions.
3. Remove the Old Coil: Remove the old ignition coil, taking care not to damage any surrounding components.
4. Install the New Coil: Install the new ignition coil, ensuring it sits securely in its mounting location.
5. Reconnect the Wires: Reconnect the wires to the new ignition coil, making sure they’re properly connected to the correct terminals.
6. Test the New Coil: Start the engine and check for a good spark at the spark plug.

Troubleshooting Tips

If you’re still having trouble with your lawn mower‘s ignition system, consider these additional troubleshooting tips:

• Check the Spark Plug: A faulty spark plug can also prevent the engine from starting. Inspect the spark plug for wear, carbon buildup, or cracks. Replace it if necessary.
• Inspect the Wiring: Check the wiring leading to the ignition coil, spark plug, and other components for loose connections, corrosion, or damage.
• Test the Battery: A weak battery can also affect the ignition system. Test the battery voltage and replace it if necessary.
• Check the Ignition Switch: A faulty ignition switch can prevent power from reaching the ignition coil. Test the switch for continuity and replace it if necessary.

Time to Mow!

By following these steps and troubleshooting tips, you should be able to diagnose and potentially fix an ignition coil problem on your lawn mower. Remember to always prioritize safety by disconnecting the spark plug wire before working on the ignition system. With a little patience and knowledge, you’ll have your lawn mower roaring back to life in no time!

Answers to Your Most Common Questions

Q: Can I use a universal ignition coil for my lawn mower?

A: While universal ignition coils exist, it’s crucial to ensure they’re compatible with your specific lawn mower model. Check the coil’s specifications and compare them to your mower’s requirements.

Q: How long does an ignition coil typically last?

A: The lifespan of an ignition coil varies depending on usage, maintenance, and environmental factors. Generally, they can last several years, but they can be prone to failure if exposed to excessive heat, moisture, or vibrations.

Q: What are the signs of a bad spark plug?

A: Signs of a bad spark plug include a black, sooty appearance, a cracked insulator, or a gap that’s too wide or too narrow.

Q: What are the risks of running a lawn mower with a faulty ignition coil?

A: Running a lawn mower with a faulty ignition coil can lead to engine damage, as the spark plug might not ignite the air-fuel mixture consistently. This can result in misfires, rough running, and even engine stalling.

Q: Can I replace the ignition coil myself?

A: Replacing an ignition coil is a relatively simple task that most DIYers can handle. However, if you’re uncomfortable working with electrical components or your lawn mower has a complex ignition system, it’s best to consult a qualified mechanic.