How to Replace Spark Plug in Small Engine: Small Engine Guide

Spark plugs are a small but crucial component in the ignition system of small engines, such as those found in lawnmowers, chainsaws, and snowblowers. Their primary function is to ignite the air-fuel mixture within the engine's combustion chamber. This is achieved through an electrical spark that arcs across two leads in the spark plug, igniting the mixture and creating an explosion that powers the engine. The timing of these sparks is critical for the engine's smooth and efficient operation.

Over time, spark plugs can wear out. This wear primarily occurs at the electrode, where the electrical arc causes tiny amounts of material to erode away. Eventually, the electrode shortens, affecting the spark plug's ability to create an effective spark. This can lead to misfires, where the fuel-air mixture in the engine's cylinders isn't ignited properly. Misfires can have damaging effects on the engine and its components, such as the catalytic converter.

The lifespan of spark plugs varies, but most car manufacturers recommend changing them every 50,000 kilometers. However, "extended life" spark plugs made from more durable metals can last up to 160,000 kilometers. Signs that spark plugs may need replacement include the check engine light being on, engine rattling or knocking, difficulty starting or accelerating, and poor gas mileage.

To replace spark plugs, a set of specific tools and materials is required. The essential tools include:

A socket wrench with an extension which is crucial for reaching the spark plugs.Spark plug sockets come in two main sizes, 5/8 inches and 13/16 inches, and usually have a rubber insert to hold the plug snugly. You should also prepare a spark plug socket. This is a specialized socket that fits over the spark plug. A swivel head spark plug socket and an extension might be necessary for hard-to-reach plugs.

You can also consider some needle-nose pliers. They are pretty useful for removing and handling small parts, especially in compact engine spaces. Make sure you have the gap gauge to measure and adjust the gap between the spark plug electrodes. This will help you ensure it matches the manufacturer's specifications.

For materials, you will need new spark plugs, and they must be the correct type and size for your engine.

Before beginning, it’s important to clean the work area around the engine to prevent debris from entering the cylinders. Check the gap on the new spark plugs and adjust if necessary using the gap gauge. When installing the new plugs, apply the correct torque using a torque wrench. Consult the vehicle’s manual or a professional for specific torque specifications and spark plug gaps for your particular model​.

Replacing the spark plug in a small engine, such as those found in lawn mowers, snow blowers, or garden tillers, is a straightforward process that can greatly improve the performance of your equipment. Here’s a step-by-step guide:

Step 1: Safety First

Before you begin, ensure the engine is off and cool. Disconnect the spark plug wire to prevent accidental starting.

Step 2: Locate the Spark Plug

Find the spark plug on your engine. It's typically visible on the side of the engine and has a thick wire attached to it.

Step 3: Remove the Old Spark Plug

First, clean around the spark plug to prevent debris from falling into the combustion chamber. Use a spark plug socket and a ratchet or wrench to carefully unscrew and remove the old spark plug from the engine.

Step 4: Check and Set the Gap

Using a spark plug gap gauge, check the gap on the new spark plug against the manufacturer's specifications for your engine. Adjust if necessary by bending the ground electrode slightly.

Step 5: Install the New Spark Plug

Carefully thread the new spark plug by hand to avoid cross-threading. Once hand-tight, use the spark plug socket and wrench to snug it up. Be careful not to over-tighten, which can damage the threads.

Step 6: Reattach the Spark Plug Wire

Firmly press the spark plug wire onto the new spark plug until it clicks or feels securely in place.

Step 7: Test the Engine

Start the engine to ensure it's running smoothly. If the engine does not start or runs poorly, double-check your work, ensuring the spark plug is properly gapped and installed, and the wire is securely attached.

Remember, regular maintenance of your small engine, including timely spark plug changes, can extend the life and efficiency of your equipment. Always refer to the engine's manual for specific instructions and safety guidelines related to your particular model.

Regularly inspect your spark plugs, at least once a month or every 50 hour use. Look for signs of wear, deposits, or damage. If you notice any issues, address them promptly to avoid engine problems.

Regular cleaning of the spark plug is also crucial. Remove any dirt or debris using a wire brush or specialized cleaner. This prevents buildup that can affect performance. For a thorough clean, remove the plug, soak it in a petrol, diesel, or isopropyl alcohol solution, then gently clean with sandpaper or a tiny file, especially the electrodes.

Be aware of symptoms like difficulty starting the engine, poor acceleration, rough idle, and decreased fuel economy. These can indicate worn-out spark plugs that need attention.

Replacing the spark plug in your small engine is a vital maintenance task that can vastly improve the engine's performance. By following these steps, you can ensure a successful replacement, extending the life and efficiency of your small engine. Remember, a little effort in maintenance goes a long way in ensuring the reliability of your equipment.

1. How often should I replace the spark plug in my small engine?

Replacing the spark plug in your small engine typically depends on usage and engine type. Most manufacturers recommend checking and potentially replacing the spark plug every season or after 100 hours of use. Always refer to your engine's manual for specific guidance.

2. What tools do I need to replace a spark plug in a small engine?

To replace a spark plug in a small engine, you will need a spark plug socket, a ratchet or wrench, a spark plug gap gauge (to check and adjust the gap if necessary), and possibly needle-nose pliers for removing the spark plug wire.

3. How do I know which spark plug is right for my small engine?

The correct spark plug for your small engine will be specified in your engine's manual. Spark plugs vary in size and heat range, so it's important to use the one recommended by the manufacturer. Using the wrong spark plug can lead to engine problems.

4. What are the steps to replace a spark plug in a small engine?

Disconnect the spark plug wire and make sure the engine is cool. Use a spark plug socket and wrench to remove the old spark plug. Check the gap on the new spark plug and adjust it if necessary using a gap gauge. Thread the new spark plug by hand first to avoid cross-threading, then tighten with the socket and wrench. Firmly attach the wire to the new spark plug. Then Start the engine to ensure it's running properly.

5. What should I do if the engine doesn’t start after replacing the spark plug?

If the engine doesn't start after replacing the spark plug, double-check that the spark plug wire is securely connected. Also, ensure that the new spark plug has the correct gap and is properly tightened. If the problem persists, there may be other issues with the engine requiring professional diagnosis