Troubleshooting a chainsaw with a flooded engine

Ever been ready to get to work with your chainsaw, only for it to sputter and refuse to start? A flooded engine can really throw a wrench in your plans. Signs like excessive smoke, a strong fuel smell, or spark plugs soaked in fuel mean something’s off. Knowing how to clear a flooded engine can get you back on track and tackling those cutting jobs without a hitch.

The information in this article may not apply exactly to your specific appliance model. For the most accurate guidance, it’s best to check your manufacturer’s documentation or reach out to us if you have any questions.

How to identify a flooded chainsaw engine

• Strong smell of fuel: If you catch a strong gas smell around the chainsaw (especially near the exhaust or spark plug area), it’s a classic sign of too much fuel in the engine.
• Wet spark plug: Remove the spark plug and take a look. If it’s wet or soaked in fuel, the engine is flooded. A flooded plug won’t spark properly, which keeps the saw from starting.
• No start after multiple pulls: If you’ve pulled the starter cord more than a few times with no results, especially with the choke on, you’ve probably added too much fuel to the cylinder.
• Popping or sputtering but not starting: Sometimes you’ll hear the engine try to fire with a “pop” or short burst but then nothing—this usually means there’s too much fuel and not enough air.
• Excessive smoke or fuel dripping: In severe cases, you might see smoke puffing out or even raw fuel dripping from the exhaust or carburetor area.
• Hard to pull starter cord:  If there’s a lot of fuel in the cylinder, it can create resistance and make the starter rope harder to pull than usual.

Why chainsaw engines flood

• Too many pulls with the choke on: Over-priming or excessive pulling while the choke is engaged sends too much fuel into the engine.
• Incorrect starting sequence: Not following the proper start procedure can cause fuel to build up without ignition.
• Pressing the primer bulb too many times: Over-priming with the bulb forces excess fuel into the carburetor and cylinder.
• Dirty or clogged air filter: A blocked air filter restricts airflow, throwing off the fuel-air mixture and causing flooding.
• Stuck or leaking carburetor needle valve: This can let fuel continue to flow into the engine even when it’s not needed.
• Flooded spark plug: If the plug is wet with fuel, it won’t spark properly, preventing ignition and adding to the flooding.
• Low-quality or stale fuel: Poor combustion or incomplete ignition from old fuel can cause unburned fuel buildup.
• Repeated failed start attempts: Every unsuccessful pull continues adding fuel to the cylinder, leading to flooding over time.
• Throttle not open during starting: Starting without opening the throttle (on some models) can lead to a rich mixture that floods the engine.

Safety precautions   

When working on any appliance, remember to keep safety first. Here are some tips to keep in mind: 

• If working indoors, make sure there is adequate ventilation to prevent the buildup of exhaust fumes. Carbon monoxide poisoning can be a serious risk.
• Wear insulated work gloves to protect your hands from sharp metal parts, pinching hazards and debris.
• Never attempt to service or repair while it is running or when the engine is still warm. Wait for all moving parts to come to a complete stop.
• Exercise extreme caution when working near blades, augers, or any other moving parts. Keep your hands, fingers, and clothing clear of these areas at all times.
• If the appliance has recently been used, give it plenty of time for any hot parts to cool down before working on it. 
• Empty the gas tank before beginning any work. Refill using fresh fuel. 
• Clean up oil spills right away to prevent slipping or other damage. 
• When working with wires, avoid touching any exposed wires or terminals. If you need to touch a wire, use a non-conductive tool or wear insulating gloves to prevent electrical shock.
• Take your time and don’t rush while working to prevent accidents and personal injuries.
• Work in a well-lit area so you can clearly see and access the interior parts.
• Clear your workspace of clutter and other obstacles. Keep children and pets away from the work area.
• Be gentle when handling or removing parts. Excessive force might damage the appliance or cause injury.
• Wear safety glasses when working with chemicals, dust or cleaning large debris to prevent injury. 
• When not in use, store the machine in a safe and dry location.

Steps to clear a flooded chainsaw engine

1. Turn off the choke: If the choke is still on, turn it off. Keeping it on will continue adding fuel and make things worse.
2. Engage the throttle: On many models, you can lock the throttle open (wide open position) using the trigger lock or throttle lock. This helps more air move through the engine to clear out the fuel.
3. Switch the ignition ON: Make sure the ignition switch is in the “on” position before you start pulling.
4. Pull the starter cord 6–10 times: Pull the cord several times with full throttle and no choke. This helps push the extra fuel out through the exhaust. Don’t worry if it doesn’t start yet, just focus on venting the fuel.
5. Remove and inspect the spark plug: Take out the spark plug using a socket wrench. If it’s wet with fuel, dry it off with a clean rag or use compressed air. Let it air out for a few minutes if needed.
6. Pull the starter cord a few more times with the plug out: This vents any remaining fuel from the cylinder. Be sure the ignition is off during this step to avoid accidental sparks.
7. Reinstall the dry spark plug: Once it’s clean and dry, screw it back in and reconnect the spark plug wire.
8. Start the engine with no choke and throttle open: Try starting the saw again without the choke and with the throttle engaged. It may take a few pulls, but it should fire up.

Pro Tip: To avoid flooding next time, follow the manufacturer’s recommended cold start procedure closely and don’t over-prime or choke longer than necessary.

Moving forward

If you get stuck or want more resources, check out AppliancePartsPros.com. We’ve got parts and info to help keep your chainsaw humming for your next project.

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