Grass line trimmers—also called string trimmers—are a great lawn and garden tool for cutting grass and weeds where the mower can't reach, and for edging next to pavement. But problems with the cutting line can make the trimming job frustrating. Fortunately, there are solutions. Here are three common problems with the cutting line in line trimmers and what to do about them.
For additional and more specific information, refer to the owner's manual that came with your trimmer. For step-by-step instructions for common repairs, see our repair guides for grass line trimmers.
Line wears or breaks quickly
It's normal for the cutting line to wear down as you use it, but the trimmer line can wear faster than you expect if you're cutting tough or thick weeds, if you're cutting against hard surfaces such as rocks and walls, or if the line is spinning too fast.
To preserve cutting line when cutting thick weeds or against hard surfaces, don't crowd the trimmer head into the area you're cutting. Instead, slide the cutting head slowly toward the cutting area so you use the tip of the cutting line. And ease off on the throttle to properly control the speed of the cutting head, especially when cutting against hard surfaces.
Old cutting line can become brittle and prone to breaking. If your line is more than 5 years old and breaks often, replace it.
If you find yourself replacing trimmer line frequently, try using fresh round line—square and star-shaped lines tend to wear faster.
Cutting line advances too much
Each bump-feed and automatic-feed line trimmer has a small blade set into its guard that prevents the cutting line from getting too long. That blade eventually gets dull, and it can sometimes break off. If either case, the line feeds out farther than you expect, possibly slicing into fences, flowerbeds, trees or your shins. Fortunately, it's usually easy to replace a dull or broken cutting blade.
Cutting line doesn't advance
If you keep stopping because the new line isn't feeding out, you most likely have a problem with your trimmer head or spool of nylon line. Stop the engine. Disconnect the spark plug on a gas-powered trimmer or unplug an electric trimmer to make sure the machine doesn't turn on while you're fixing it. Then take a close look at the trimmer head and do one of the following:
If the spool is empty, replace it.
If the ports on the trimmer are clogged with grass or dirt, clean them out and wipe any debris from the line remaining on the spool.
If the cutting line is twisted, pull it off of the spool and rewind it carefully, making sure the loops don't cross.
If the line has stuck to itself, or "welded," due to heat, unwind the line, cut away the section that has melted or fused together, and then rewind the remaining line. If the problem keeps recurring, try using a higher-quality line labeled as "anti-weld" or "anti-fuse." Those lines have higher melting temperatures.
If you see no line sticking out of the ports on the trimmer head, you may not have bump-fed the line often enough. Push the bump head down with one hand and pull out line with your other hand until you can touch the cutting guard with the tip of the line. You may have to remove the trimmer head cover and manually feed line through the port.
The fuel line on a grass line trimmer deteriorates with time and eventually can split or crack. You can replace it yourself, following these instructions.
If the line trimmer won't start even though there's fuel in the tank, the carburetor could be the problem. Follow these instructions to replace the carburetor in under 30 minutes.
If the line trimmer engine won't start even though there's fuel in the tank, the carburetor could be the problem. Follow these instructions to do the job in under 30 minutes.
Use the advice and tips in these articles and videos to get the most out of your grass line trimmer.
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Find out how to take care of your grass line trimmer from the start of the trimming season until the end, with this helpful maintenance checklist.