Do String Trimmers Have Spark Plugs?

String trimmers are the best way to take care of the stubborn patches of grass your lawn mower can’t reach. One common issue many users can run into is that their string trimmer refuses to start working at all, and wonder – could it be the spark plug at fault? Do string trimmers, like lawnmowers, even have spark plugs?

In fact, string trimmers do have spark plugs and need them to be able to work. The plug provides the ‘spark’ of electricity needed to make the string trimmer move and function. However, you need the right spark plug to work with your string trimmer. When replacing one, ensure it can reach the right components and is no larger than 1 inch. 

Not being able to use your string trimmer can leave your lawn looking unkempt – and no one wants that! So if you want to understand how a string trimmer can work with a spark plug, whether they are universal or not, and what kind of length to look out for, this is the perfect article for you!

The Role Of A Spark Plug In A String Trimmer

Many people may not notice, but you can owe the functionality of your string trimmer to a tiny component known as the spark plug. This component’s key responsibility is to create an electrical spark, which causes an ignition within the trimmer. 

This ignition triggers the mixture of fuel and air inside your string trimmer. As a result, the fuel combusts, giving you the energy you need to use the string trimmer on your lawn. 

Like any other component in your trimmer, there is always a chance that issues can come up with the spark plug, especially over time. If there is wear and tear on your spark plug, or you notice that it has started to accumulate dirt, the trimmer will not be able to work. 

This can reduce the efficiency of your string trimmer, and may affect its functionality. Therefore, it is essential that you replace your spark plug if the previous one has failed. 

Are Spark Plugs Universal?

If you are in the position where you have decided to replace your spark plug, the next course of action is to find one that can fit into your trimmer. You may then wonder – is there anything distinct about the different kinds of spark plugs? 

The fact of the matter is, there are a lot of differences that make each spark plug uniquely suited for its role in a string trimmer, as there are other applications in mowers, cars, and other vehicles. 

So while spark plugs can seem similar, they are in fact very distinct, and it is important to choose the right kind of spark plug if you want to get your string trimmer back in working condition. 

Unfortunately, you cannot just reuse an old spark plug (and doing so may not be the wisest decision in terms of efficiency) as it may not be able to create the same level of functionality or reaction that it normally does. For a spark plug to work in your trimmer, it needs to be the right size, and have the correct reach, and temperature features. 

What Kind of Spark Plug Does A String Trimmer Take?

If you are on the lookout for a new spark plug that your string trimmer can take, you will need to consider a lot of things. Here are some of the factors to keep in mind when choosing a spark plug for your string trimmer

Factor Requirement For A String Trimmer
Temperature  500-800 degrees Celsius
Size Around ¾ (0.75) inches
Gap Must be precisely 0.03 inches
Material Can be any, copper is the most cost-effective

An overview of requirements for a small engine spark plug, such as a string trimmer engine.


As you can imagine, a spark plug needs to be able to manage a suitable firing temperature in order to create fuel combustion and avoid any issues such as overheating. 

This measure is known as the firing end temperature, which you should keep as a consideration. 

The ideal range for a spark plug like this is between 932-1472°F (or 500-800°C) to keep a steady temperature without causing any carbon fouling or overheating issues. 


A string trimmer, such as other smaller gardening tools, requires a specialized size spark plug that is specifically designed for use in a smaller engine. 

In this case, you need to use a spark plug that is no bigger than 3/4ths of an inch, or 0.75 inches. If you are getting a new spark plug, always make sure to check if that is the correct size, as car spark plugs can be around 14mm (0.55 inches) in size. 


If you are replacing your spark plug on your string trimmer for the first time, you will need to have a gap between the ground electrodes and the center electrodes to be able to use the plug effectively. 

In the case of a string trimmer, this distance needs to be exactly 0.03 inches in size. This is the only way your spark plug can ignite the engine correctly. 


One of the biggest factors that can change how well your spark plug can work is the kind of material the electrodes are made out of. 

The three most common options that can be used are copper, platinum, and iridium. You can use any kind of material for a spark plug in your string trimmer engine. 

However, since you will be using a spark plug for a smaller engine, a copper electrode will be just fine in accomplishing the work. 


How long can a string trimmer spark plug last?

Your string trimmer’s spark plug will last you for about 25 hours of use, which should be enough to last you an entire season in most cases. 

Can I clean a spark plug and then reuse it?

While you can clean your spark plug and reuse it, it is generally not recommended. Spark plugs are inexpensive and easy to replace, and a used one may not result in the efficiency you need in your string trimmer. 

Final Thoughts

In conclusion, string trimmers do indeed have spark plugs, and it is important to ensure that they are working properly for the trimmer to function effectively. It is crucial to choose the right kind of spark plug for your specific trimmer, taking into account factors such as temperature, size, gap, and materials. 

If all else fails, you can always look up the manufacturer’s recommendation for spark plugs in the user’s manual or on the internet. 

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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