Spark Plug Check

This article will cover the spark plug check if you have run into problems with your petrol hedge trimmer engine.


It is important to check and test the spark plug because it generates the spark needed to ignite your engine.

Removing and Checking the Spark Plug


Spark plug spanner tool

Removing Spark Plug

  1. Take off the spark plug cap (the thick black rubber cable which goes over the plug, also called the high tension lead).
  2. Unscrew the spark-plug anti-clockwise using the spark plug spanner tool. This may require some force.

Checking the Condition of Spark Plug

Please ensure that the spark plug is not dirty. When it gets covered in carbon, it can prevent the plug from sparking properly. If dirty, clean the end of the spark plug, preferably with a wire brush, or with a cloth dabbed in petrol.

Testing Spark Plug for a Spark

  1. Remove the spark plug, as described above.
  2. Make sure the plug is clean, as described above.
  3. Plug the spark plug back into cap, so that the end is dangling off.
  4. Lean the tip of your spark plug against a metal part of your machine to earth it.
  5. Make sure your Start/Stop switch is switched onto START.
  6. Make sure you are in a shaded area so that you can observe it sparking.
  7. Pull your starter chord strongly and observe the tip of your spark plug.
  8. You should see a faint white flash - this indicates that the spark plug is working.
  9. If you see no flash, then it could mean that your spark plug is not working.

Testing a different spark plug

  1. If you have another petrol machine which is working correctly, you can take its spark plug off and test it on your machine as described above.
  2. If this other spark plug is sparking, then this means that your current spark plug is at fault.
  3. If it doesn't spark, then this means that your electrics are faulty - you will most likely need to replace the ignition coil. 

Reinserting the Spark Plug

  1. Once the spark plug has been cleaned and/or tested you may refit the spark plug into the engine.
  2. Screw the plug in by hand to prevent cross threading, then use the tool to tighten.
  3. Refit the cover, ensuring it clicks into place.