Your string trimmer isn’t running like it normally does. It starts and runs, but now you must have your choke on in order to keep it running. Finding and fixing this problem will help you get the best performance from your trimmer.
A Shindaiwa string trimmer that only runs with the choke on is either not getting enough fuel or it is getting too much air. The choke may need to be on when the Shindaiwa string trimmer is running old gas; the carburetor is dirty; the fuel filter or vent is plugged; a fuel line is punctured, or the carburetor gasket is bad.
Remove the spark plug wire. Wait for the engine to cool and all parts to stop moving before performing any repairs to your Shindaiwa trimmer.
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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.
6 Reasons a Shindaiwa String Trimmer Only Runs With the Choke On
Old Gas
Old gas is not good for your Shindaiwa. It can leave behind varnish and gummy deposits that restrict the fuel flow and cause damage to the components. Using the right gas and consuming it quickly can reduce the negative effects experienced by running old gas.
Because gas begins to break down as quickly as 30 days after purchase, it’s important to only use fresh fuel in your string trimmer. Shindaiwa string trimmers run a 2-cycle engine which requires a gas and oil mixture at a ratio of 50:1.
Use unleaded gasoline with an octane rating of 89 or higher and a maximum ethanol content of 10%. Mix with a premium 2-cycle oil.
Read more about choosing and caring for the fuel in your string trimmer at “This is the Type of Gas and Oil Shindaiwa String Trimmers Use“.
Solution: Remove old gasoline from your string trimmer. Add fresh fuel that includes an additive like Sea Foam to stabilize the gas, clean the fuel system and reduce moisture.
Note: Some oils contain a fuel stabilizer, but they don’t always last that long. Read the information on your bottle to find out how long fuel will be stable.
Hole in the Fuel Line
A hole or small puncture in the fuel line can cause your Shindaiwa string trimmer to suck in air providing the engine with more air than it requires. Because of the added air, the choke will have to be on to restrict airflow so the engine receives the right ratio of gas to air it requires to run.
While you are looking for punctures also check for fuel leaks that may prevent sufficient fuel to the engine.
Solution: Remove and replace any damaged or cracked fuel line.
Plugged Fuel Filter
A plugged fuel filter can cause a lack of fuel to the engine requiring a reduction in the air to maintain a good fuel-to-air ratio. You will need to run your string trimmer with the choke on to reduce the air intake.
When your Shindaiwa fuel filter isn’t changed regularly or you’re running very dirty fuel, it can become plugged not allowing sufficient fuel to pass through the filter. It’s best to stay on top of your fuel filter maintenance by changing it out annually and more often if needed.
Solution: Replace a plugged fuel filter. The filter is located inside the fuel tank. Wipe around the fuel tank cap before removing it to keep dirt from falling into the tank. Pull the filter out of the tank.
A clean bent wire works well to “fish” the filter out of the tank. Remove the old filter and attach a new fuel filter to the end of the fuel line and place it back inside the fuel tank. Reinstall the fuel cap.
Bad Carburetor Gasket
The gasket that sits behind the carburetor can become bad and no longer create a good seal. When this happens, additional air is allowed into the system causing it to run lean. This is when there is a higher concentration of air and less fuel than required by the engine.
Solution: Gain access to the carburetor and carefully remove the linkages and bolts attaching the carburetor. Remove the carburetor and gasket. Reinstall a new gasket and reattach the carburetor, bolt, and linkages.
When you remove the gasket to check it, you will have to replace it whether it is bad or still good. Be prepared and have a replacement gasket on hand. You may need to clean the carburetor while it is off the string trimmer.
Dirty Carburetor
The carburetor’s function on a Shindaiwa is to regulate the amount of fuel that is mixed with air to form a combustion to start and run the string trimmer.
A buildup of varnish and deposits left behind by old gas can make the carburetor not function right so the correct ratio of fuel to air is not being mixed.
You may need to have the choke on to help correct the ratio so your Shindaiwa trimmer continues to run.
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 remove deposits left behind from old fuel.
If the carburetor does not function after being cleaned, you may need to rebuild it or replace it with a new carburetor.
You can also bring your Shindaiwa string trimmer to a small engine repair shop to have the carburetor cleaned or replaced if you are not comfortable doing this. Note: the repair shop may just replace the carburetor instead of taking time to clean it.
This isn’t necessarily a bad thing. The amount of labor that will be charged to remove, clean, and reinstall a carburetor may be equal to or more than the cost of just replacing it with a new one.
Plugged Fuel Vent
The fuel tank must be vented to allow air into the tank to equalize the air pressure. Without a vent, the fuel tank will create a vacuum that will prevent fuel from flowing to the engine.
A good indication you may have a fuel tank vent problem is when your string trimmer runs for a few minutes and then shuts down and won’t start until you remove the fuel cap to allow air into the fuel tank. It then shuts down again after running for several minutes once you reinstall the fuel cap.
Shindaiwa string trimmers use a fuel tank vent that is attached to the fuel line coming out of the fuel tank.
Solution: Replace a plugged fuel tank vent to allow air to flow into the fuel tank.