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Your Lawn Edger is Running Rough (8 Things to Troubleshoot)

A lawn edger that begins to run rough will not give you the power you need to get that clean line between the lawn and your sidewalk.

An edger will begin running rough when the engine isn’t getting the correct air, fuel, and spark required for combustion.

This may be due to a plugged air filter, wrong choke setting, plugged spark arrestor, fouled spark plug, plugged fuel filter, dirty carburetor, clogged fuel line, or old fuel.

Stay safe and follow the safety precautions provided in your operator’s manual. This includes removing the spark plug wire and waiting for all moving parts to stop.

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Follow all safety instructions provided in your equipment operator’s manual before diagnosing, repairing, or operating. Consult a professional if you don’t have the skills, or knowledge or are not in the condition to perform the repair safely.

Reasons Your Edger is Running Rough & Bogs Down

1. Old or Bad Fuel

Gasoline can have negative effects on your edger. It’s important to use the correct fuel and properly care for it. Old fuel attracts moisture that can leave behind varnish and gummy deposits that clog the fuel system and cause components to fail.

Because gasoline breaks down as quickly as 30 days after purchase, it’s important to use fresh gas and consume it within this time frame.

If you are unable to use a tank of fuel this quickly, add a fuel additive like Sea Foam to stabilize it and reduce the negative effects of fuel.

Most handheld edgers use a 2-cycle engine while most walk-behind edgers use a 4-cycle engine. However, this doesn’t mean you won’t find handhelds with a 4-cycle engine and walk-behinds with a 2-cycle engine.

Edgers with 2-cycle and 4-cycle engines have different fuel requirements.

  • 2-cycle engines: Require a gas and oil mix. The mix ratio varies by manufacturer. It is often a 40:1 or 50:1 mixture.
  • 4-cycle engines: Require straight gas. Do not mix fuel with oil for these types of engines. There will be a separate fill port for engine oil.
    * An exception to this is STIHL’s 4-MIX engines. These engines are designed to use a 50:1 gas-to-oil mixture.

Don’t add the wrong fuel to your edger. Doing so can damage the engine beyond repair.

2. Dirty Spark Plug

A dirty or damaged spark plug can cause it to misfire causing the edger to run rough. A loose spark plug wire or incorrect gap can also be responsible for a poorly running edger that bogs down.

Remove the spark plug using a socket wrench. Check its condition. Replace the spark plug if you find the tip is very dark in appearance, the porcelain is cracked or the electrode is burnt.

If you find your spark plug is just dirty, clean it with a wire brush or replace it with a new spark plug.

Check the spark plug gap using a feeler gauge. Install the new or clean spark plug and make sure the spark plug wire is securely attached.

3. Plugged Fuel Filter

The fuel filter attaches to the end of the fuel line and sits in the fuel tank. Fuel is filtered to prevent dirt and debris from entering the fuel system.

When the filter becomes clogged so a good steady flow of fuel isn’t able to pass through the filter, the edger will begin to run rough because it isn’t getting sufficient fuel.

A plugged fuel filter must be replaced.

Replace an edger fuel filter:

  • Set the lawn edger on a flat surface.
  • Wipe around the fuel cap to remove dirt around the fuel cap.
  • Remove the fuel tank cap.
  • Take note of the position of the fuel filter so you place the new filter in the same position.
  • Pull the fuel filter out of the tank using clean bent wire or needle nose pliers.
  • Remove the filter from the fuel line and install a new filter.
  • Position the new filter correctly inside the fuel tank.
  • Install the fuel cap.

4. Clogged Fuel Lines

The fuel lines can become clogged if dirt gets into the fuel system. Gummy deposits left behind from running old fuel can also cause a blockage.

Look for a clog or a kink in the fuel line that can cause the edger to run roughly from a lack of fuel. Replace any fuel lines when you find a restriction, fuel leak, or dry cracked lines.

5. Plugged Fuel Tank Vent

The fuel tank vent can become plugged or damaged preventing air from passing through the vent to equalize the air pressure in the fuel tank. A plugged vent can cause a vacuum to form in the fuel tank to keep fuel from flowing out of the tank.

If fuel isn’t running through the fuel lines and you don’t have a clogged line or a plugged fuel filter, there is a good chance the fuel tank vent is plugged.

You can test this by loosening or removing the fuel cap to allow air into the tank. Start the edger, and allow it to run.

Be careful and keep your edger level so you don’t spill any gas from the tank. If the edger runs strong and doesn’t bog down and run rough, tighten the fuel cap and see if you can replicate the issue to confirm the fuel tank vent is the problem.

Replace the fuel tank vent if your edger starts to act up and run rough again after installing the fuel cap. On some edgers, the tank vent is a separate component installed to a line coming out of the fuel tank. On others, the vent is built into the cap.

6. Plugged Air Filter

The engine requires air to run. Without enough air, the edger will run sluggish and rough. One of the items that can restrict airflow is a plugged air filter.

The air filter can become plugged from dirt and debris when not regularly cleaned and changed.

If you find your air filter is very dirty, I recommend replacing the filter. The small air filter is usually not very expensive. It is an important component when it comes to protecting the engine.

Clean an edger FOAM, FELT, and FABRIC air filter:

  • Remove the air filter from the housing.
  • Wipe out any dirt remaining in the housing. Be careful to not let any dirt fall into the air intake.
  • Wash the filter with a mild detergent and water to remove dirt.
  • Rinse until the soap is removed. Lay it flat to dry.
  • FOR SOME FOAM FILTERS: Once the filter is dry, coat the filter in clean engine oil. Squeeze to remove excess oil. DO NOT APPLY OIL to felt, fabric, or paper air filters.
  • If the filter is excessively dirty, damaged, or no longer seals the air intake, you must install a new filter.
  • Install the clean filter and reattach the air filter cover.

Because there are so many different types of filters used which varies by manufacturer and model of the edger, refer to your operator’s manual for steps to clean the style of air filter in your lawn edger.

7. Dirty Carburetor

The carburetor mixes the correct proportion of air and fuel needed for your edger to run. The passageways can become clogged and the small components can fail to function correctly.

This can cause an insufficient amount of fuel mixed with air resulting in a rough running edger.

You may be able to clean your carburetor to get it working again. You may end up having to rebuild (if rebuild kits are available for your carburetor) or replace the carburetor if cleaning doesn’t help.

8. Plugged Spark Arrestor

There is a small metal screen that keeps hot exhaust material from shooting out of the edger and causing injury or starting a fire. This small screen will become plugged with a carbon buildup that will affect how the engine runs.

Solution: Disconnect the spark plug wire. Remove the engine cover and the engine exhaust cover. Carefully remove the spark arrestor screen. Clean the spark arrestor screen using a wire brush and reinstall it.

If the screen isn’t able to be sufficiently cleaned or you find it is damaged or has a hole in it, replace it with a new spark arrestor screen.