What to do when a weed trimmer will not stay running

Written by cleveland van cecil | 13/05/2017
What to do when a weed trimmer will not stay running
(grass image by Thomas Quinlan from Fotolia.com)

Weed trimmers are simple, two cycle engines that run a blade or a string reel to cut grass in small areas and to clean up corners in your landscaping projects. With the right kind of maintenance, a weed trimmer is easy to keep in good working condition. When your weed trimmer will not stay running, run through the basic troubleshooting steps to get it working again.

Initial Troubleshooting

Check that the gas in your weed eater is filled to the right level and is fresh. Stale fuel is a common issue in weed trimmers. When a weed trimmer is stored for a long period of time, the gasoline will go bad. If the fuel has been in the tank for a few months, change it with fresh fuel. If you have a weed eater where fuel and oil need to be mixed together, make sure the mixture is not too heavy either way. Follow the instructions on your engine oil container to get the right mixture. Do not mix more than you will be able to use within 30 days.

Adjusting Carburetor

Adjust your carburettor if the engine cuts out when idling or at high speed. Look for a two small screws on your weed trimmer carburettor that has a slot for a flat head screwdriver. One screw will be marked H, for high speed, while the other will be marked L, for low speed. The high screw will adjust the fuel mixture given when the trimmer is running at its highest speed, and the low screw will control fuel mixture for the idle speed. To adjust the L screw, start the weed trimmer and turn the screw counter clockwise until the speed of the engine decreases. Do this again clockwise. Remember these two points and position the screw so that it is somewhere between the two extremes. Adjust the H screw the same way. This will ensure that the fuel mixture of the engine is correct so that excess air or excess fuel will not cause the engine to cut out.


Make sure your choke is in the correct position as you are running your weed trimmer. The choke supplies the fuel to the engine to aid the starting process when the trimmer is cold. When starting, the choke needs to be in the highest position, or full choke. As the engine attempts a start, the choke should be moved to the half choke position, then completely disengaged when the engine starts. Having the choke in a high position as the trimmer is running will cause it to cut out. If you have a faulty choke that moves easily, or is stuck in the full position, you will not be able to run your weed trimmer properly and will have to replace the component.

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