How Often Should You Replace a Spark Plug In a Trimmer?

If you own a trimmer or a lawnmower, you’ll know replacing spark plugs is the most crucial maintenance task. If it isn’t working correctly, your engine will sputter and stop functioning later. There’s a fair chance of a spark plug being the culprit if your trimmer stops working. So, how often should you replace your spark plugs?

Typically, you should replace spark plugs around the beginning of every season or when the trimmer has been used for 25 hours. However, the range of hours may vary with brands and their model specifications. Study the brand’s manual to determine how often you should change the spark plugs. 

If you own an electric trimmer or a lawnmower, this information does not apply to you because spark plugs are only present in fuel-powered trimmers. In this article, we’ll discuss how to change, replace and care for your spark plugs to get good performance results for your gas-powered trimmer. 

How Do You Check And Replace a Sparkplug In a Trimmer?

If you haven’t tuned your engine lately, then a faulty spark plug might be the reason for your dead machine. If it doesn’t start on the first few tries and you have to pull the cord multiple times for it to start, then there’s a good possibility your spark plug is done. 

However, this might not be the only problem; you can have other issues like dusty cylinder heads, diluted oil, and excessive fuel use. 

When To Check Spark Plugs?

Electrodes on the spark plug must be kept clean and sharp for a vital spark. Worn-out and dirty spark plugs require more voltage and greater tugs to pull the cord so a sufficient spark can be produced.

Good for you; spark plugs are easily accessible and are a simple component of your machine that is highly inexpensive to repair or replace. For the standard model of a lawn trimmer and usual engine maintenance, you should run a regulatory check;

  • Once every season,
  • After 25 hours of running the machine, 
  • Or if the power equipment doesn’t start. 

How to Check for a Faulty/Dead Spark Plug?

You can check for bad spark plugs using the following steps. The machinery might vary a bit depending on your brand and model. 

Step 1: Take off the spark plug lead from the trimmer. Clean the plug area to avoid dust and debris getting inside the combustion chamber after removing the lead. 

Step 2: Get a spark plug socket (Amazon link) to remove the plug. 

Step 3: If you see small deposits on the plug, clean them using a wired brush and a liquid plug cleaner spray. 

Step 4: Check if there are strong deposits on the spark plug, cracking porcelain, or if the electrodes are burnt. If any of these previous issues are there, replace the plug. 

Step 5: If there’s a gap in the spark plug, adjust the spacing. 

Step 6: If the spark plug seems operable, place it back carefully but try not to over-tighten it. Now you can put the spark plug lead back in its place. 

Step 7: Start the engine to check if the spark plug is working fine. 

If the engine has a problem starting, for instance, it tries to turn over for a bit but dies with a spark; then the problem lies somewhere else. This indicates the fault is either in the fuel, carburetor, valves, etc. 

If the engine doesn’t start, the ignition system might be dead. This is when you introduce a new spark plug to your engine.

What Affects Spark Plugs?

Spark plugs aren’t made to last as long as a string trimmer. The electrodes connected to the spark plugs deteriorate over time when each spark is produced, becoming shorter and blunter. Once worn, they have trouble making enough spark to turn the engine on and keep it running.

The following are some other elements that might harm spark plugs or possibly render them useless:

The Oil Present In The Combustion Tank

As seals age, oil can flow into the area where the plug ignites over time. As a result, the spark plug’s tip becomes fouled with oil, harming it and reducing its lifespan. 

Your spark plug may not be functioning correctly if your trimmer is burning oil.

Carbon Buildup

When you take out your spark plug, you could notice that it is covered in a layer of black soot. This is probably the result of carbon buildup. 

This accumulation, brought on by junk infiltrating the region where the spark plug ignites, may also damage the component.


Another factor is overheating, which contributes to early plug damage brought on by a malfunctioning cooling system. 

The terminals on the plug are worn down, and the spark is strained by repeated overheating.


Q. What Is the Lifespan of a Spark Plug in a Trimmer?

Spark plugs typically last about 25 hours. Spark plugs are a problem regardless of how carefully you maintain your trimmer. They can quickly wear out after being used for an extended period of time. 

Q. How Can Foul Spark Plugs Be Cleaned?

Use a wire brush or spray-on plug cleaner created especially for this ignition component to clean a spark plug safely. A robust knife can also be used to scrape off stubborn deposits.

Q. How Can You Tell if Your Spark Plug Is Damaged?

If your trimmer’s engine can’t ignite while having adequate fuel, it’s likely that the problem lies in the spark plugs. They could either be dirty or might need a replacement. 

Final Thoughts

You’re lucky if your spark plug turns out to be the issue! It’s an easy remedy that sometimes only requires a thorough cleaning. Knowing what to check for and when to replace your trimmer’s spark plug is an excellent method to keep your machine in good working order and with fewer issues. 

The most common cause of starting problems with trimmers is undoubtedly a lack of petrol, but spark plug problems are also a common cause. 

Peter Toth

Hi! I'm Peter, the owner of BackyardGadget. Working around the house has always been a big part of my life. I've created this site to share my experience, and to help people choose the right tools for the job. Thank you for stopping by!

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