How to Troubleshoot a Weedeater

Weed eaters are used to improve the landscape.
Weed eaters are used to improve the landscape. (Image: Weed image by Necroborg from

Weed eaters are ideal for cutting grass and plants where lawnmowers cannot reach. Weed eaters have various shapes and sizes but share many common problems. Problems with power, fuel and the trimmer head can lead to malfunctioning in a weed eater. Because of these common issues, troubleshooting a weed eater can be accomplished when you know the nature of the problem and how to approach it.

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No Power

Check the settings on the weed eater. Make sure the choke, ignition switch and throttle are in the correct positions. The choke must be closed and the throttle open for fuel to flow through the system. The ignition must be on to fire the spark plug.

Look at the fuel mix. The fluid should be a light brown or bronze color; if it is dark or black it must be changed before it clogs the trimmer motor.

Inspect the spark plug. Disconnect the spark plug wire from the spark plug. Remove the spark plug and inspect the head for damage or wear. Clean out the spark plug chamber, the plug and the end of the wire. Reconnect the spark plug to the weed eater. Reconnect the wire to the spark plug.

Remove the cover of the fuel filter and examine the filter. The filter may be clogged and should be changed every other year at a minimum.

Low Power

Check the gas-to-oil ratio of the fuel mix. Do not use straight gasoline without adding oil or you will damage the engine. The engine will run on an incorrect ratio of gas and oil, but it will run hard with little power.

Clean the air filter. This is a foam filter that can be clogged from dry grass, weeds and debris picked up during the operation of the weed eater. Lack of air to the filter causes lack of air to the engine, which in turn causes loss of power.

Use Step 4 in the first section to check the carburetor and fuel filter. Inconsistent or incorrect flow of fuel through the carburetor into the engine will cause a loss of power because the engine will run too lean or rich. A screwdriver can adjust the screws to the carburetor.

Power Loss

Listen for low-sounding noises when you have loss of power. This signifies a filter problem. Unscrew the knob on the carborator to check the filter. Filters with any dark coloration need to be cleaned. Compressed air can clean the filter.

Check the fuel line for air bubbles. This means you have cracks or leaks in the line. Replace the fuel line.

Look for clogs in the air hose or around the moving parts. Grass dust, pollen or debris can get caught in the intake during operation and can occur over time. Use compressed air to clean the clog. Never use water because this causes dust and dirt to stick to the engine.


Use the proper fuel mixture for your machine. This is the most common problem for weed eater malfunction. Consult the owner's manual for the proper mixture. Drain the weed eater completely of the fuel. Use a gas container specifically marked for this type of fuel mix. Remix the fuel in the can. Make sure you are using two-cycle oil in the mix.

Check the age of the fuel if you see dark smoke. This means the fuel mix is burning inside the engine. Replace the fuel with a fresh supply.

Check the spark plug and carburetor if you see white or grey smoke. This means dirt or water has entered the fuel and the engine. This occurs if the weed eater is left in rain or used during rain.

Winterize the weedeater at the end of the season. The fuel may gum up, causing a residue along the inside of the fuel line and engine causing rough running or stalling.

Trimmer Head

Check for clogs at the trimmer head. Wet grass or tall weeds are the most likely cause. Remove debris from around the trimmer head. Remove the spool and clean out the chamber.

Replace the line if the trimmer doesn't cut properly. Use the owner's manual to determine the correct string for replacement.

Align the trimmer line if the head pops off. Remove the spool and remove the line. Restring the spool with fresh line and reassemble the trimmer head following the arrows on the chamber.

Tips & Warnings

  • To avoid injury or property damage, keep the trimmer head in the air or have the tool laid down when starting and stopping.
  • Disconnect the power supply before doing anything with the trimmer motor or head to avoid burns or cuts.
  • When exchanging bad fuel for good, you may need to run the weed eater for a few minutes to burn off the residue of the remaining bad fuel before using the weed eater.
  • Spend the extra money for heavier line if you are cutting thick weeds or brush; thinner line will snap and wear quickly.


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