My Petrol Strimmer/Brush Cutter is not running properly

This guide covers a number of basic checks you can perform if your petrol strimmer or brush cutter is difficult to start, runs poorly, or will not run at all.

Tools Required

• Spark plug spanner

Contents

• Removing the Spark Plug
• Checking the Condition of the Spark Plug
• Testing the Spark Plug for a Spark
• Testing with a Different Spark Plug
• Reinstalling the Spark Plug

Removing the Spark Plug

1. Remove the spark plug cap (the thick black rubber lead attached to the spark plug, also known as the high-tension lead).
2. Using the spark plug spanner, turn the spark plug anti-clockwise to remove it.
3. Some resistance is normal and moderate force may be required.

Checking the Condition of the Spark Plug

Inspect the spark plug for signs of dirt, carbon build-up, or damage.

A spark plug covered in carbon deposits may not produce a strong spark, which can affect engine performance or prevent the engine from starting.

If the spark plug is dirty:

1. Clean the electrode end using a wire brush where possible.
2. Alternatively, wipe it carefully with a cloth lightly dampened with petrol.
3. Allow it to dry completely before testing or reinstalling.

Testing the Spark Plug for a Spark

Note: This test is easier and safer with two people.

1. Remove the spark plug as described above.
2. Ensure the spark plug is clean.
3. Reconnect the spark plug to the spark plug cap.
4. Position the metal body of the spark plug against a clean metal part of the machine to create an earth connection.
5. Ensure the Start/Stop switch is set to START.
6. Move to a shaded area where the spark is easier to see.
7. Pull the starter cord firmly while observing the tip of the spark plug.
8. Look for a small white or blue spark.

Results

• A visible spark indicates the spark plug is functioning correctly.
• No spark may indicate a faulty spark plug or an issue with the ignition system.

⚠️ Warning: Keep hands clear of the spark plug electrode during testing to avoid electric shock.

Testing with a Different Spark Plug

If you have access to another working petrol machine:

1. Remove the spark plug from the working machine.
2. Connect it to your machine's spark plug cap.
3. Repeat the spark test described above.

Results

• If the replacement spark plug produces a spark, your original spark plug is likely faulty and should be replaced.
• If neither spark plug produces a spark, there may be a fault with the ignition system, such as the ignition coil.

Reinstalling the Spark Plug

1. Carefully screw the spark plug into the engine by hand first to avoid cross-threading.
2. Once finger-tight, use the spark plug spanner to tighten securely.
3. Refit the spark plug cap, ensuring it is pushed fully into place.