You rely on your string trimmer to reach places your mower can’t reach. It helps finish the lawn’s manicured appearance by cutting grass around landscaping, trees, fence posts, water features, and more.
When your string trimmer loses power, it can get frustrating to try to trim grass when it gets pushed over or wrapped around the trimmer head.
A Ryobi string timmer will lose power when it isn’t getting sufficient air, fuel, or spark required for the engine to perform at its best. Carbon deposit buildup in the exhaust port, muffler, and spark arrestor screen can also result in a loss of power.
Reasons a Ryobi string trimmer has no power:
- Old gasoline
- Plugged air filter
- Dirty spark plug
- Plugged fuel filter
- Clogged fuel line
- Plugged fuel tank vent
- Plugged spark arrestor
- Carbon buildup on the exhaust port
- Dirty carburetor
This post may include affiliate links. Purchases made through these links may provide a commission for us, at no extra cost to you. As an Amazon Associate, we earn from qualifying purchases.
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 a Ryobi String Trimmer Has No Power
Old Gasoline Causes Loss of Power in a Ryobi String Trimmer
Old gas or the wrong type of gas can be the culprit for so many problems in your Ryobi strimmer including a loss of power. Gas sitting for longer than 30 days will begin to break down becoming less effective.
It’s important to use fresh gas in your Ryobi trimmer and add a stabilizer to the gas when you are unable to use it this quickly. If you don’t do this, gas will have negative effects on your trimmer due to fuel restrictions, engine damage, or failed fuel components.
Most gasoline include ethanol. This is an alternative fuel that is added to make gasoline a little more environmentally friendly. Ethanol is not a good product for the small engine on your Ryobi string trimmer.
Because ethanol is harmful to a small engine, it is best to only use fresh gasoline with an ethanol content of 10% or less. Never use fuels with higher ethanol contents than this like fuels sold as E15, E30, and E85 fuel. These have ethanol contents up to 15%, 30%, and 85% respectively.
Ethanol isn’t good for your trimmer because it attracts moisture from the air. This water and ethanol mixture will corrode components and leave behind gummy deposits that can clog and cause fuel system failure.
The water and ethanol mixture will also separate from the gas after sitting for a long period of time. This mixture runs hot through the engine potentially damaging it.
Your Ryobi string trimmer requires unleaded gasoline with a minimum octane rating of 89 and a maximum ethanol content of 10%. The lower the ethanol content or an ethanol-free fuel is best.
Before you add fuel to your Ryobi string trimmer, determine whether your trimmer has a 2-cycle or 4-cycle engine. They have different fuel requirements. A 2-cycle engine uses a gas and oil mix. A 4-cycle engine uses straight gas.
For more information on fuel, read “This is the Type of Gas and Oil Ryobi String Trimmers Use“.
Solution: Drain the fuel remaining in your string trimmer and fill it with fresh fuel for your engine type. Add a fuel stabilizer like Sea Foam Motor Treatment. This product will not only stabilize your fuel, but it will also reduce moisture and clean the fuel system.
Plugged Air Filter in a Ryobi String Trimmer
An air filter is used on a string trimmer to protect the engine from wearing due to dirt and debris. An air filter keeps this dirt out while allowing clean air through the filter.
When the filter isn’t regularly replaced or cleaned, the air filter will become plugged restricting the amount of air that is able to pass through the filter. This lack of air will cause your Ryobi string trimmer to lose power.
Remove the air filter cover. Remove the filter and wipe out any remaining dirt and debris from the housing and cover. Check the air filter for a buildup of dirt plugging the filter.
Solution: If you find your Ryobi air filter is plugged, I recommend replacing it with a new one. A filter is usually not very expensive. It is an important component when it comes to protecting the engine. Follow these steps if your filter is in good condition, undamaged and you choose to clean it:
A foam-style air filter can be cleaned using a mild dish soap and water. Wash the filter to remove as much dirt as possible. Rinse until the water runs clear.
Lay flat to dry. Once dry, lightly saturate the filter with clean engine oil or air filter oil. Squeeze the filter to remove any excess oil. Install the air filter and attach the cover.
Consult your operator’s manual for instructions when cleaning other types of air filters.
Dirty Spark Plug in a Ryobi String Trimmer
A fouled spark plug can cause it to misfire resulting in a loss of power from your Ryobi string trimmer. A damaged or dirty plug covered in carbon must be cleaned or replaced.
In addition to checking for a dirty spark plug, you will need to verify the spark plug gap meets the manufacturer’s specification and the spark plug wire (boot) is securely attached. These are also items that can cause your string trimmer to not run properly.
Solution: Remove the spark plug and replace it when you find it is extremely dark in color or damaged. Make sure the new spark plug is gapped correctly before installing.
It is possible to clean a spark plug using a wire brush if it is in good condition other than being a little dirty. I prefer to replace this maintenance item to ensure it’s in good working condition because the spark plug is a vital component of a well-running string trimmer.
Plugged Fuel Filter in a Ryobi String Trimmer
You will find the fuel filter located inside your Ryobi’s fuel tank. The filter should be changed out annually or after every 25 hours of use, whichever comes sooner. When the fuel filter isn’t replaced regularly, it can become plugged and cause your trimmer to lose power.
Solution: Replace a fuel filter that isn’t allowing gas to pass through to the fuel line. Check your fuel tank to make sure the fuel is of good quality and it’s not contaminated with dirt and debris. If the fuel is very dirty or old, replace the fuel.
Clogged Fuel Line in a Ryobi String Trimmer
The fuel line can become restricted with gummy deposits left behind from using old fuel. These can prevent a good flow of fuel to the engine resulting in power loss.
Solution: Inspect the fuel line looking for any clogs preventing fuel flow. Replace a fuel line on your Ryobi string trimmer that is clogged, kinked, or has developed cracks from age.
Plugged Fuel Tank Vent on a Ryobi String Trimmer
The fuel tank vent also called a check valve can become plugged 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 keeping 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 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 the trimmer 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.
Solution: The fuel cap contains a non-serviceable filter and check valve. If you are having problems with the vent in the cap no longer working, you must replace it with a new fuel cap.
Plugged Spark Arrestor in a Ryobi String Trimmer
The spark arrestor is a small metal screen that prevents hot exhaust material from leaving the muffler and starting a fire. When this small screen becomes plugged you may experience a loss of power where your Ryobi string trimmer won’t run at full RPMs.
Solution: Disconnect the spark plug wire. Remove the engine cover and the engine exhaust cover. Carefully remove the spark arrestor screen and clean it using a wire brush.
Install the clean spark arrestor screen. Reattach the engine exhaust cover and engine cover. Reattach the spark plug wire.
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.
Carbon Buildup on the Exhaust Port in a Ryobi String Trimmer
The exhaust port located behind the muffler can develop carbon deposits that can cause your Ryobi string trimmer running problem. This area should be checked and cleaned when you are experiencing a loss of power that hasn’t been fixed by the items above.
Solution: To avoid damage to the trimmer, Ryobi recommends you have an experienced mechanic clean the exhaust port and muffler. If you choose to attempt to clean it, first disconnect the spark plug wire and make sure the engine and muffler are cool so you don’t burn yourself.
Remove the engine cover, the muffler, and the heat shield. Adjust the piston until it covers the port opening. This will keep carbon from falling into the cylinder.
Use a plastic scraper to remove the carbon buildup around the exhaust port. DO NOT use a metal tool. Do not scratch the piston or the cylinder during this process. Reinstall the items in the reverse order you removed them.
Dirty Carburetor Causes a Ryobi String Trimmer to Lose Power
A carburetor is required on a string trimmer to regulate the amount of gas mixed with air to create a combustion. Old fuel can gum up and cause the small components in your carburetor to stick so it no longer functions right.
Solution: If you are a little mechanical you should be able to handle cleaning your carburetor. Clean the carburetor by taking it apart and using carburetor cleaner to clean it.
If the carburetor does not function after being cleaned, you may need to rebuild it or replace it with a new carburetor.
When to Have a Mechanic Repair Your Ryobi String Trimmer?
You may have gone through the items above and it didn’t solve your Ryobi string trimmer’s lack of power. You may just not feel comfortable performing repairs on your string trimmer. That’s okay.
Find a small engine mechanic or an outdoor power equipment store that has a repair shop to assist you.
Keep in mind the labor rate for the mechanic to diagnose your problem. There is typically a flat rate charge to diagnose the problem and then add labor and parts fees in addition to the fee to make the repairs.
This may not make sense if you are running an old inexpensive string trimmer that’s on its last leg. Having your Ryobi string trimmer repaired by a mechanic is a personal decision that only you can make.
You have the weigh the reliability, quality, and age of your current string trimmer against the cost of the repair.