Your leaf blower is still running, but something is just not right with it. It only runs on full choke or half choke. Even though it continues to start and run, you need to find and fix the problem before it develops into a larger one.
A leaf blower that only runs with the choke on is either not getting enough fuel or is getting too much air. This can be from running old gas, a hole in the fuel line, a plugged air filter, a dirty carburetor, a bad carburetor gasket, or a plugged fuel vent.
I have listed some troubleshooting and repair steps below. If these items do not fix your leaf blower; you are unsure of how to complete the repair; or you simply feel you don’t have the mechanical skillset to work on your blower, contact your nearest dealer or small engine repair shop for assistance.
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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 Leaf Blower Only Runs With the Choke On
Old Gas
Old gas sitting in a leaf blower will cause fuel restrictions that may cause it to run at half choke or with the choke on. The choke reduces the amount of airflow so the blower has the right ratio of gas to air required to stay running.
Because gas begins to break down after 30 days and can leave varnish and gummy deposits behind, it’s important to only use fresh fuel in your leaf blower
Use gasoline with a minimum octane rating of 89 and a maximum ethanol content of 10%. Using gas with higher ethanol contents can cause engine damage.
Leaf blowers with 2-cycle engines require oil to be mixed with the gas. Leaf blowers with 4-cycle engines require straight gasoline (no oil mixed in). Read more about choosing and caring for the gas in your leaf blower at “This is the Type of Gas and Oil Leaf Blowers Use“.
Solution: Remove old gasoline from your leaf blower. Add fresh fuel that includes an additive like Sea Foam or STA-BIL to stabilize the gas, clean the fuel system and reduce moisture.
Hole in the Fuel Line
You may have to use the choke when there’s a puncture in the fuel line or air is finding its way into the fuel system. Inspect the fuel lines and find a puncture or loose line where the air is being sucked into the line. You will also need to look for any fuel leaks at this time.
Solution: Remove and replace any damaged or cracked fuel line. Make sure the fuel lines are securely attached.
Plugged Fuel Filter
A fuel filter is used to keep dirt from entering the fuel system. It can restrict fuel flow when it isn’t changed regularly and becomes plugged with dirt and debris. I recommend replacing the filter annually to avoid running into this problem.
You will need to change it more often if you add dirty fuel to the tank. I highly advise against using old and dirty fuel. You may want to save a little money and not waste old fuel, however, in the long run, you may damage the carburetor or engine.
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.
Be careful and don’t lose the retaining right that is used to secure the fuel line to the filter. Reinstall the fuel cap.
Bad Carburetor Gasket
The gasket that sits behind the carburetor can deteriorate and become worse over time. When this happens, it no longer seals properly allowing additional air 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. The choke may need to be on to compensate for the extra air being pulled into 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. You may need to clean the carburetor while it is off the leaf blower.
Dirty Carburetor
The carburetor’s function is to regulate the amount of fuel that is mixed with air to form combustion to start and run the leaf blower. A buildup of varnish and deposits can make the carburetor not function as designed so it isn’t able to get fuel to the engine.
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 the 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.
Depending on the model leaf blower you run, the price of the carburetor, and the age of the blower, it may be best to invest in a new leaf blower rather than put money towards replacing a carburetor on an old leaf blower.
You can also bring your leaf blower 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 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 through the leaf blower.
A good indication you may have a fuel tank vent problem is when your leaf blower runs for a few minutes and then shuts down and won’t start until you loosen or 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.
Depending on the manufacturer and model of your leaf blower, the fuel tank vent may be a check valve in the fuel cap or it may be an independent vent located off of a fuel line coming out of the fuel tank.
Solution: Replace the fuel tank vent or fuel tank cap (depending on your model leaf blower) so air can flow into the fuel tank.