When your string trimmer begins to bog down and run rough, it won’t give you the power you need to get your trimming job done. The job may take a lot longer and the trimmer may not give you a nice even trim.

An ECHO string trimmer runs rough due to old fuel, a dirty carburetor, a clogged fuel line, a plugged fuel filter, a dirty spark plug, a plugged fuel tank vent, a clogged air filter, or a plugged spark arrestor screen.

Take caution when working on your string trimmer. Follow all safety precautions found in the ECHO operator’s manual. This includes removing the spark plug wire, waiting for all parts to stop moving, and allowing the engine to cool.

ECHO string trimmer dirty air filter

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Follow all safety instructions provided in your equipment operator’s manual prior to 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.

8 Reasons Your ECHO String Trimmer Runs Rough & Bogs Down

Old or Bad Fuel Causes an ECHO String Trimmer to Run Rough

The first thing I suspect when an ECHO string trimmer begins to run rough and bog down is the fuel quality. Old fuel can begin to break down and become less effective as soon as 30 days after purchase.

Most gasoline includes ethanol, a plant-based fuel, that naturally attracts moisture to the fuel system. When the ethanol and water mixture evaporates, it leaves behind gummy deposits and varnish.

The lack of fuel due to the varnish and deposits causing restrictions in the fuel system will result in a sluggish string trimmer.

The type of fuel and how quickly it is consumed are important to obtain good performance from your trimmer. Getting the fuel selection right and caring for it properly will reduce the problems that develop from running old gas.

The type of gas you use to fill the fuel tank is one thing you don’t want to get wrong. Gasoline can have negative effects on your string trimmer when you don’t use the right type of gas or you let the gas sit in your trimmer and get old.

Keep these items in mind when selecting fuel for your string trimmer:

  • Purchase fresh unleaded gasoline with a minimum 87-octane rating and maximum 10% ethanol content.
  • Mix gas and 2-cycle oil mix at a ratio of 50:1 before adding to the fuel tank for ECHO string trimmer 2-cycle engines. Read more about fuel in This is the Type of Gas and Oil ECHO String Trimmers Use.
  • Consume fuel within 30 days.
  • Add a fuel stabilizer if you are unable to consume fuel within 30 days so it lasts a little longer.
  • Store fuel indoors in a dry location away from combustible items.

Read more about choosing and storing fuel in This is the Gas and Oil Fuel Mix ECHO String Trimmers Use.

SOLUTION: Empty old fuel from the fuel tank. Mix 50 parts unleaded gasoline with 1 part 2-cycle oil in a gas container. Add a fuel additive like Sea Foam Motor Treatment to stabilize the fuel and clean the fuel system.

Add the fuel mixture to the fuel tank and allow it to run so the new fuel works its way through the system. The ECHO string trimmer may begin to run better. If it doesn’t, proceed with checking the remaining items in the list until you find one that works.

Plugged Fuel Filter Causes an ECHO String Trimmer to Run Rough

Continue checking other items that may be causing a fuel restriction. Inspect the fuel filter. This is the small cylinder-shaped part that can be found inside the fuel tank attached to the fuel line.

When the filter isn’t changed out regularly, it can become plugged with dirt keeping a good flow of fuel from getting to the carburetor. This will cause the trimmer to run rough and bog down.

SOLUTION: A plugged ECHO fuel filter must be replaced using the following procedure:

  • Set the trimmer on a flat surface.
  • Wipe around the fuel cap, and then remove it.
  • Pull the fuel filter out of the tank using a clean bent wire to hook the fuel line.
  • Securely holding the fuel line, securely grab the filter and pull it out of the fuel line.
  • Install a new fuel filter at the end of the fuel line.
  • Place the filter back inside the fuel tank.

Clogged Fuel LinesCause an ECHO String Trimmer to Run Rough

Inspect the fuel line and look for a clog or a kink that restricts the amount of fuel that is able to flow through the line. Clogs can develop from dirty fuel or gummy deposits left behind by running old fuel.

SOLUTION: Replace an ECHO line with a new fuel line when you find a clog, kink, puncture, or leak in the line.

Dirty Carburetor Causes an ECHO String Trimmer to Run Rough

The carburetor is the part that regulates the amount of gas that is mixed with air that is needed to form combustion so the ECHO starts and runs.

When this proportion of gas to air is not correct, the string trimmer may begin to run rough. The passageways in the carburetor can become clogged and the small components that make up the carburetor can stick.

This can cause the ECHO carburetor to fail to function properly and get enough fuel to the engine.

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

Damaged carburetors due to old fuel running through them are a common issue.

Minimize carburetor damage by using fresh fuel. Avoid the negative effects ethanol has on the carburetor by using a non-ethanol fuel like pre-mixed ECHO Red Armor 50:1 fuel.

Dirty Spark Plug Causes an ECHO String Trimmer to Run Rough

A fouled spark plug on your ECHO can cause it to misfire and run sluggishly. A damaged spark plug, an incorrect spark plug gap, and a loose spark plug wire can also result in running problems with your string trimmer.

SOLUTION: 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 in good condition and 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 to make sure it matches the engine manufacturer’s required specifications. Install the new or cleaned spark plug. Make sure the spark plug wire is securely attached.

Plugged Fuel Tank Vent Causes an ECHO String Trimmer to Run Rough

The fuel tank must have a vent to allow air to pass through. When this vent becomes plugged, the fuel tank will form a vacuum keeping fuel from flowing out of the tank and to the carburetor.

A fuel tank vent on an ECHO string trimmer is a small part attached to the end of a line coming out of the fuel tank. When the engine isn’t able to get enough fuel due to a plugged fuel tank vent, it will run rough.

If you are not getting fuel and you don’t have a restriction due to a clogged fuel line, plugged fuel filter, or dirty carburetor, your problem may be a plugged fuel tank vent.

You can test for a plugged fuel tank vent by loosening the fuel cap to allow air into the tank. Start the trimmer, and allow it to run. Be careful and keep your string trimmer level so you don’t spill any gas from the tank.

If your ECHO trimmer runs strong and doesn’t bog down or run rough, tighten the fuel cap and see if you can replicate the issue to confirm the fuel tank vent is the problem.

SOLUTION: Replace the fuel tank vent if your trimmer starts to act up and run rough again after reinstalling the fuel cap. The cap contains a non-serviceable filter and check valve that must be replaced when the fuel tank is unable to vent.

Plugged Air Filter Causes an ECHO String Trimmer to Run Rough

An air filter is essential to run on an ECHO string trimmer. It provides protection to the engine by keeping dirt out of the air intake.

When the air filter isn’t checked, cleaned, and replaced to keep a clean filter on your trimmer, it can become plugged with so much dirt that sufficient air isn’t able to flow through the filter.

Without enough air, the engine will begin to run rough. It’s important to keep the air clean to protect the engine and not cause it to overheat due to a lack of air.

SOLUTION: Inspect the air filter and clean it if it is in good condition using the steps below. If the filter is very dirty, fuel-covered, or damaged, it must be replaced with a new one.

Steps to clean an ECHO string trimmer felt-type air filter:

  • Remove the air filter cover from the housing.
  • Remove the dirt remaining in the housing using a dry clean cloth.
  • Inspect the filter. If it is in good condition and not damaged, covered in fuel, or very dirty, proceed with cleaning the filter.
  • Lightly brush the dirt from the air filter. If lightly brushing doesn’t work, wash the filter in a mild detergent and water mix. Lightly brush the dirt from the filter. Allow the filter to air dry until it is completely dry.
  • Reinstall the air filter.
  • Reattach the air filter cover.

Because there are so several different types of air filters used on ECHO products that can vary by model, refer to the ECHO operator’s manual for steps to clean a different style of an air filter.

Plugged Spark Arrestor Causes an ECHO String Trimmer to Run Rough

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

Disconnect the spark plug wire. Remove the engine cover and the engine exhaust cover. Carefully remove the spark arrestor screen with a metal brush.

Install the clean spark arrestor screen. Reattach the engine exhaust cover and engine cover. Reattach the spark plug wire.

If the screen cannot be sufficiently cleaned or you find it is damaged or has a hole in it, it must be replaced with a new spark arrestor screen.

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