One of my earliest memories is standing in an orchard with my father while he cut firewood with an old green Poulan chainsaw. As a kid, that saw seemed like the most capable machine in the world.
Chainsaws are less impressive when the starter cord has been pulled ten times, the engine still refuses to fire and the air smells strongly of petrol.
A flooded chainsaw has too much fuel and too little air inside the engine. Stop priming it, turn the choke off and give the excess fuel a chance to clear. Repeated pulling with the choke engaged usually makes the flooding worse.
How to Start a Flooded Chainsaw in 5 Steps
Stop adding fuel. Do not press the primer bulb again. Move the choke to the run or off position and confirm that the ignition switch is on.
Let a mild flood clear. Leave the chainsaw sitting for 15 to 20 minutes so some of the excess fuel can evaporate.
Prepare the saw safely. Engage the chain brake, place the saw firmly on level ground and set fast idle according to the instructions for your model.
Pull with the choke off. Use several short, firm starter pulls. Stop after about 10 to 15 attempts rather than continuing indefinitely.
Inspect the spark plug. If the engine still will not fire, remove and dry or replace a wet spark plug, ventilate the cylinder safely and then repeat the correct startup sequence.
Never use a lighter, torch or open flame to dry a spark plug. Petrol vapour can ignite even when the fuel source appears to be several feet away.
How to Tell if Your Chainsaw Is Flooded
Flooding usually happens after the engine has been primed or choked repeatedly without starting. Each failed attempt draws more fuel into the cylinder until the mixture becomes too rich to ignite.
The strongest clues are:
- A powerful smell of petrol around the saw.
- A starter cord that has been pulled repeatedly with no sign of ignition.
- A spark plug that is wet with fuel when removed.
- The engine fired briefly, then died after the choke remained engaged.
- Fuel is visible around the muffler, carburettor or air-filter area.
Check the fuel before blaming flooding. A stale two-stroke oil and petrol mixture can produce similar starting problems. Fuel that has been sitting for more than a month may need to be drained and replaced.
Method One: Let the Excess Fuel Evaporate
The 15-Minute Reset
```This is the safest and easiest method for an engine that has only been mildly flooded.
- Place the chainsaw on a stable surface in a well-ventilated area.
- Move the choke control to the run or off position.
- Do not touch the primer bulb.
- Leave the saw alone for 15 to 20 minutes.
- Engage the chain brake and attempt the normal warm-start procedure described in the manual.
This same waiting method can help clear mildly flooded lawnmowers, trimmers and weed-eater engines.
```Start with this method. Removing a spark plug creates more opportunities for fuel spills, damaged threads and accidental ignition, so it should remain the second option.
Method Two: Clear a Stubbornly Flooded Engine
When waiting does not work, you can try to clear the engine with the choke off and the throttle set for starting.
Clear the Engine Without Removing the Plug
```- Engage the chain brake fully.
- Move the choke lever to the run or off position.
- Set fast idle according to the starting controls fitted to your saw.
- Confirm that the ignition switch is on.
- Place the saw securely on level ground with the guide bar clear of people and objects.
- Hold the front handle firmly and place your foot through the rear handle where the manufacturer permits this starting position.
- Pull the starter rope with short, firm movements until the engine fires.
The saw may produce smoke or run unevenly for a few seconds as it burns the excess fuel. Release fast idle as soon as the engine settles.
Stop after about 10 to 15 pulls. Endless pulling can overheat the starter mechanism, exhaust the operator and continue drawing fuel through some carburettor systems.
What to Do if the Spark Plug Is Wet
If the engine still refuses to start, the spark plug may be wet-fouled. A coating of fuel across the electrodes can prevent the spark from igniting the mixture.
Safe Spark-Plug Clearing Procedure
```- Turn the ignition switch off and let the engine cool.
- Work outside, away from cigarettes, heaters, sparks and open flames.
- Remove the spark-plug boot and clean loose debris from around the plug.
- Use the correct plug wrench to remove the spark plug without damaging its threads.
- Inspect the electrodes. A wet coating confirms that excess fuel has reached the cylinder.
- Wipe the plug with a clean cloth and leave it in a ventilated place until completely dry. Replace it if it is fouled, damaged or heavily worn.
- With the ignition off and the plug removed, point the spark-plug opening away from yourself and pull the starter several times to ventilate the cylinder.
- Allow any released petrol mist to disperse before reinstalling the plug.
- Refit the plug carefully by hand before tightening it with the wrench. This reduces the risk of cross-threading the cylinder head.
- Reconnect the boot and follow the manufacturer’s warm-start procedure.
Do not automatically prime the carburettor after clearing a flood. The engine may already contain enough fuel to start. Follow the exact starting sequence in the manual for your model.
If the spark plug is old, cracked or repeatedly wet-fouled, replacement may be the quickest answer. The same basic inspection principles apply when you replace a small-engine spark plug.
Why Chainsaws Flood So Easily
A cold two-stroke engine needs a richer fuel mixture to start. The choke restricts airflow so the carburettor supplies a mixture with a higher proportion of fuel. That helps a cold engine fire, but only for a short part of the startup sequence.
Leaving the choke engaged after the first sign of ignition continues feeding an overly rich mixture into the cylinder.
Pressing the primer bulb more times than the manual recommends can overload the carburettor with fuel.
Every unsuccessful starting attempt may draw more fuel into an engine that has still not produced a reliable spark.
A dirty air filter reduces the amount of air entering the carburettor, making the fuel mixture richer than intended.
A fouled or worn spark plug may fail to ignite the mixture, allowing unburned fuel to accumulate in the cylinder.
Stale petrol loses volatility and becomes harder to ignite, leading to repeated starting attempts and eventual flooding.
How to Prevent a Chainsaw from Flooding
- Use fresh two-stroke fuel. Mix only what you expect to use within about a month, unless the fuel or stabiliser manufacturer specifies a longer storage period.
- Prime only as directed. More presses do not produce a stronger start.
- Listen for the first pop. Once the engine briefly fires on full choke, move immediately to half choke or run according to the manual.
- Keep the air filter clean. Restricted airflow makes the mixture rich and increases starting problems.
- Inspect the spark plug. Replace a worn, carbon-fouled or damaged plug before it causes repeated failures.
- Use firm starter pulls. Short, decisive pulls turn the engine fast enough to generate a strong ignition spark.
- Learn the controls on your saw. Choke, half-choke and fast-idle arrangements differ between brands and models.
The most useful prevention habit: read the starting sequence in the manual once and follow it exactly. Many flooding problems begin when the operator treats every chainsaw as though its choke and primer controls work the same way.
When Flooding May Not Be the Real Problem
A petrol smell and wet plug point strongly toward flooding, but persistent starting trouble may have another cause.
- A blocked fuel filter or damaged fuel line.
- A carburettor diaphragm that has hardened or split.
- A blocked spark-arrestor screen in the muffler.
- Low engine compression.
- An ignition coil or kill-switch fault.
- Water, dirt or the wrong oil ratio in the fuel.
If a fresh plug, fresh fuel and the correct clearing procedure do not restore normal starting, further carburettor or ignition diagnosis may be required.
Watch the Starting Procedure
Keep the Chainsaw Cutting Properly
The Bottom Line
A flooded chainsaw usually needs less fuel, more air and a little patience. Stop priming, turn the choke off and begin with the 15-minute waiting method. If that fails, clear the engine with firm starter pulls before removing the spark plug.
Once the saw is running again, work out why it flooded. Excessive choke, too much priming, stale fuel, a dirty air filter or a weak spark plug will create the same problem the next time you reach for the starter cord.
