Lawn Mower Not Sparking: Reasons and Solutions

Having trouble getting your lawnmower to spark? This problem can be frustrating, especially when you need to get your lawnmower running again.

Due to ignition system defects, a lawn mower may not spark. Like: a broken spark plug, malfunctioning ignition coil, or weak internal wire connections. A lawn mower may not fire due to an incorrect gap between the flywheel and the ignition coil or a defective stop/start button.

This article lists the most common reasons your lawnmower won’t spark and offers solutions.

Is It Bad If My Lawn Mower Not Sparking?

Yes. If your lawn mower is not sparking, it means that the spark plug is not functioning properly, which can cause problems with the combustion of the fuel.

Without a spark, your lawn mower will not be able to start or run properly. This can cause your lawn mower to stall, which can be dangerous if you are not careful when operating it.

Additionally, a lack of spark can lead to a buildup of carbon deposits in the engine, which can cause further damage and reduce the lifespan of the lawn mower.

Lawn Mower Not Sparking: Causes and Solutions

The following is a discussion of some of the potential reasons for your lawnmower’s failure to spark as well as some of the possible solutions to the problem.

1. Dirty or Damaged Spark Plug

The spark plug is responsible for generating the spark in the combustion chamber. If the spark plug is corroded or damaged, it may not generate the necessary spark.

If the spark plug is dirty, it can prevent the spark from reaching the spark plug gap and prevent the engine from firing.

Spark Plug
Spark Plug

The Fix

If your spark plug is dirty or damaged, the best thing to do is to replace it.

Inspect the spark plug for signs of wear, such as cracks, deposits, or fouling. If the spark plug is damaged, replace it with a new one of the same size and type. Clean the area around the spark plug before installation.

Once the new spark plug is installed, test your lawnmower to see if it is sparking correctly.

2. Faulty ignition coil

Faulty ignition coils can cause a lawnmower not to spark. The ignition coil is responsible for generating and transferring the high-voltage energy that is used to spark the spark plug gap. If the coil is defective, then the spark plug will not fire, and the engine will not start.

ignition coil
ignition coil

The Fix

To determine if the ignition coil is the cause of the problem, you should first check the spark plug for signs of wear or damage. If the spark plug looks fine, then you can check the ignition coil for signs of damage.

If the coil is cracked, corroded, or worn, then it will need to be replaced. You should also check the wiring for any signs of damage or wear, as this can also prevent the ignition coil from working properly.

3. Faulty Wiring

The most common cause of a lawnmower not sparking is a dirty or faulty spark plug. This can be caused by a buildup of dirt, debris, and oil on the spark plug, which prevents it from making a strong connection.

Additionally, the spark plug wire may be worn out or damaged, preventing it from sending the necessary signal to the spark plug.

The Fix

First, disconnect the spark plug from the wire leading to the ignition system. Inspect the spark plug for signs of dirt, corrosion, or other damage.

If the spark plug looks good, test the continuity of the wire with a multimeter. If the wire doesn’t have continuity, it may need to be replaced.

If the wire has continuity, check for a loose connection between the wire and the spark plug. If the connection is loose, tighten the connection and test the spark plug again.

If the spark plug still isn’t sparking, check the ignition system of the lawnmower for any loose connections or faulty wiring. If any faulty wiring is found, it should be replaced before testing the spark plug again.

4. Improper Flywheel-Ignition Coil Gap

The gap between the flywheel and the ignition coil is a critical component of the ignition system on a lawn mower. If the gap is set incorrectly, the spark plug will not be able to ignite the fuel and air mixture in the cylinder, which will result in the engine not starting.

If the gap is too wide, the spark plug may not ignite the fuel and air mixture. If the gap is too narrow, the spark may be too weak to ignite the mixture.

The Fix

To fix this issue, you need to adjust the gap between the flywheel and the ignition coil. This can be done using a feeler gauge. The gap should be set to the manufacturer’s recommended specifications.

Once the correct gap is set, the lawn mower should start and run normally.

5. Defective stop/start Button

The stop/start button on a lawn mower works by closing a circuit, which allows electricity to flow to the spark plug and ignite the engine. If the circuit is not closing correctly, the spark plug will not spark and the engine will not start.

The Fix

To fix this problem, you will need to check the wiring of the stop/start button to make sure that all of the connections are secure and that the wires are not broken or frayed.

You may also need to replace the button or switch if it is malfunctioning.

Additionally, you may need to inspect the spark plug to make sure that it is working properly. If the spark plug needs to be replaced, you should use a new spark plug that is the correct size and type for your lawn mower.

5. Clogged Fuel System

If your lawn mower is not sparking, it could be due to a clogged fuel system. If the fuel system is clogged, the fuel and air mixture will be too lean and the spark will not be generated in the combustion chamber. This can be caused by the fuel becoming contaminated with dirt, debris, or water.  

The Fix

To clean the filter, remove it from the fuel line, disassemble it, and soak it in a mixture of gasoline and lacquer thinner or carburetor cleaner.

You should also check the fuel lines for any blockages or debris. If these are clear, then you should clean or rebuild the carburetor. This can usually be done by following the instructions in the user manual or by consulting a lawn mower repair shop.

Lawn Mower Not Sparking: (FAQs)

Why does my lawn mower cylinder not fire up?

There are several possible causes for a lawn mower cylinder not firing up. These include a dirty spark plug, a faulty ignition coil, a clogged carburetor, or blocked fuel lines. Other potential causes include a dirty air filter, low fuel pressure, or a malfunctioning ignition switch.

Why is there no spark if my ignition coil is good?

For a lawn mower coil to produce a charge, it must be gapped correctly to the flywheel, have a strong magnet on the flywheel, have a functional ground wire, and be corrosion-free. So, even a tiny problem with any of these components can prohibit a fresh coil from producing a charge.

Can a bad ignition coil on a lawn mower cause engine to fail to start?

Yes, a bad ignition coil can cause an engine to fail to start. This is because the coil is responsible for generating the spark that is necessary to ignite the fuel and start the engine. If the coil is not functioning correctly, then the spark will not be generated and the engine will fail to start.

How to check the flywheel brake assembly?

Check the brake assembly by feeling for the brake pad, listening for squeaking or grinding noises, inspecting the flywheel and brake pad for wear, and testing the brake by pushing down firmly and releasing.

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