Why Is My String Trimmer Not Cutting?


After a few seasons of use, you may notice your string trimmer underperforming and cutting through grass and weeds inefficiently. Why does this happen? Why does your string trimmer stop cutting? 

String trimmers may not cut for numerous reasons, most commonly including a worn-out line and a defective slow-spinning trimmer head. Sometimes, the trimmer line may be too long or too short, preventing the machine from working properly. 

If you are tired of your string trimmer underperforming and making yard cleanup an exhausting job, keep reading! I’ve covered everything you need to know about string trimmers not cutting properly and ways to fix the issues below.

7 Reasons Why Your Trimmer Isn’t Cutting

Your string trimmer may stop cutting for various reasons. Fortunately, you can easily resolve most of them. So, you don’t need to throw out your expensive high-quality trimmer just yet! 

Let’s get started:

1) Trimmer Line Is Worn Out and/or Keeps Breaking

Trimmer lines wear down and become brittle over time. However, the three following actions can speed up the process and result in a frequently broken line: 

  • Cutting through thick and tough vegetation (taking on more than the line can handle)
  • Cutting against concrete, walls, and rocks
  • A line that spins at extremely high speeds

Here are three recommendations to prevent your line from breaking quickly: 

#1 Avoid Crowding The Trimmer Head

You can preserve your trimmer line when cutting thick vegetation or against hard surfaces by only using its tip!

Avoid crowding the head of the trimmer into an area. Instead, you should slide the cutting head toward the site to ensure you only use the tip of the line. 

#2 Avoid Using Old Lines 

You should also avoid using old lines as they are more brittle. Apart from inefficiently cutting weeds, they also break more easily. 

So, if you’re using the same line for more than 6 months, replace it. 

#3 Use The Right String For The Job

Consider using a higher-quality line that is less prone to wearing out quickly. Look for one made of reinforced nylon or co-polymers with thick diameters (0.095 inches work best with most trimmers) and twisted line shapes.

If you find that your line is breaking all the time, you can try something like the Husqvarna Titanium Force and the Oregon Magnum Gatorline Supertwist Line. Both are incredibly durable lines that can survive lots of misuses while still trimming efficiently. 

If you don’t know how to select the trimmer line that is best for you, you can check out this article.

2) Trimmer Line Is Too Long 

Automatic-feed and bump-feed line trimmers have small blades in their guards that cut the line to an ideal length. However, the blades get dull with use and stop working effectively.

Then, the line advances too much each time you bump and keeps hitting the guard, slowing the trimmer down. 

Replace the dull blade with a sharp one (or sharpen it if you can) to prevent the line from getting too long. 

3) Trimmer Line Does Not Advance 

Issues with the trimmer head or the spool will prevent a new line from feeding out. It will result in an inefficient trimmer, and you may have to stop and manually pull out the line frequently. 

Examine the trimmer head and spool and fix any issues with them.

Before beginning the fixing process, stop the engine. Then disconnect the spark plug on the gas-powered trimmers and unplug the electric trimmers. You do not want the machine to turn on while you’re working on it. 

Here are four frequently encountered issues that stop the trimmer line from advancing:

  • Empty Spool: Make sure that the spool isn’t empty (duh..!). 
  • Clogged Ports: Clean the ports in the trimmer if they are clogged with dirt and grass. 
  • Debris On Leftover Line: Sometimes, even the leftover line on the spool collects debris. It would help if you wiped it off to prevent the line from getting stuck and not feeding out.
  • Incompatible Wire: If the thickness of your line is beyond the range of your trimmer’s head, it won’t feed out. Check the diameter limitations of your trimmer and buy a line that is compatible with it. 

4) Trimmer Line Is Too Short 

You may experience the trimmer line wanting to go back into the trimmer head while trimming your yard. This is because the line outside the trimmer line is too short. 

Here are three ways to resolve the issues caused by a short trimmer line: 

#1 Bump The Trimmer Head Frequently 

You can quickly fix the issue by bumping the line out more frequently (if your trimmer has a bump-feed mechanism). Gently tapping the trimmer head on the ground will dispense more string. 

#2 Restring The Line

If bumping the trimmer head doesn’t resolve the issue, you may have strung the line incorrectly, causing it to get too short. 

Simply open up the trimmer head, access the trimmer spool, and restring it. If you are unsure about correctly restringing the line, google your trimmer’s make and model to learn how to do it properly. 

#3 Use A Heavy-Duty Line

Alternatively, a line that isn’t heavy-duty will get short faster depending on what you use it for. Simply swap out your current line with a thicker diameter one that can handle trimming rough weeds. 

5) Trimmer Line Melts Inside The Trimmer Head

Your trimmer can get too hot and melt the line inside the trimmer head, causing it to stick to the coiled-up line next to it.

Once this happens, it won’t feed out when you tap the trimmer head on the ground. So, your trimmer won’t have a line to cut the grass and weeds. 

You can fix the issue by unwinding the line, removing the part that has melted together and then rewinding the leftover line. 

If the problem occurs several times, try looking for high-quality lines labeled as “anti-fuse” or “anti-weld.” They are specially designed to have higher melting temperatures.

This only really happens if you use your trimmer for work that is harder than what it was intended for, or if you use a really low-quality line.

6) Worn-Out Trimmer Head

If the part of the head that makes contact with the ground wears out, it won’t work efficiently. As a result, the string will wear out easily. You need to replace the head to resolve this issue. 

You can identify a worn-out trimmer head easily. Do you see any external signs of damage on it, such as cracks or parts that are broken? If so, it might be a good idea to get a replacement. 

7) Slow-Spinning Trimmer Head

The trimmer head is supposed to spin and create centrifugal force. This force results in the trimmer line moving fast enough to cut through your grass and weed.

When the head doesn’t spin, the line won’t spin, therefore the grass won’t get cut. 

The head often doesn’t spin at all or spins at speeds that are too low to cut grass because of a damaged clutch or driveshaft. Fortunately, you can easily replace both of these. 

However, in some situations, damage to the trimmer head may make it unable to spin at all. You will need to replace it with a new one if this is the case. 

Final Thoughts 

Now that you know the different reasons your string trimmer could be working ineffectively, it is time to conduct a thorough inspection and figure out the cause.

Once you identify and fix it, yard cleanup will become a piece of cake. You may even find yourself enjoying the process!

Happy trimming! 

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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