It’s a frustratingly common scenario: you go to start your lawn mower, pressure washer, or generator, and it just cranks and cranks, refusing to catch. You might even smell gas. Chances are, you’ve got a flooded engine.
A flooded engine means there’s too much fuel in the combustion chamber, making it impossible for the spark plug to ignite the air-fuel mixture. The good news? For most small engines, you can often clear a flooded engine in under 60 seconds and get back to work.
Here’s your quick-fire guide to resolving a flooded engine.
Step 1: Stop Trying to Start It (5 Seconds)
The first and most critical step is to immediately stop trying to start the engine. Every additional crank just pumps more fuel into an already oversaturated cylinder, making the problem worse.
- Release the key or recoil rope.
- Wait a few seconds.
Step 2: Engage “Clear Flood” Mode (15 Seconds)
Most small engines, particularly those with carburetors, have a built-in “clear flood” mode, even if it’s not explicitly labeled as such. This mode chokes off fuel delivery and maximizes airflow.
- Move the choke lever to the “OFF” position. (This is crucial, as the choke is designed to add fuel for cold starts).
- Move the throttle lever to the “FAST” or “MAX” position. This opens the throttle plate fully, allowing maximum air into the carburetor and cylinder.
Step 3: Pull with Purpose (30 Seconds)
Now, it’s time to crank, but with a specific technique designed to push out the excess fuel.
- For recoil start engines: Give the starter rope 3-5 firm, rapid pulls. Do not slowly pull; you need quick, strong pulls to generate maximum suction and airflow.
- For electric start engines: Crank the engine for no more than 5-10 seconds at a time. Allow a few seconds between attempts to prevent overheating the starter motor.
The idea here is that the engine is getting plenty of air and no extra fuel. The rapid cranking helps to atomize and expel the excess fuel out through the exhaust.
Step 4: Listen for Life (5 Seconds)
As you pull/crank, listen carefully.
- You might hear a cough, sputter, or a brief sign of life. This indicates the engine is starting to clear.
- If it sputters but doesn’t fully start, give it one or two more pulls/cranks using the same “clear flood” settings (choke off, throttle fast).
Step 5: Return to Normal Starting (5 Seconds)
Once you hear a sign of life, or if the engine doesn’t start after 3-5 pulls/cranks in clear flood mode, revert to your standard starting procedure.
- Move the choke lever to the “START” or “FULL CHOKE” position (for cold engines) or “NO CHOKE” (for warm engines).
- Set the throttle to its normal starting position (often somewhere between $1/2$ and $3/4$ throttle).
- Attempt to start the engine as you normally would.
The engine should now fire up quickly.
What if it still won’t start?
If these steps don’t work, the flooding might be more severe, or there could be an underlying issue.
- Check the Spark Plug: Remove and inspect the spark plug. If it’s wet with fuel, clean it thoroughly with a wire brush or replace it if it’s old and worn. This is a common solution.
- Allow to Dry: Leave the spark plug out for 15-30 minutes to allow any remaining fuel in the cylinder to evaporate.
- Fuel Shut-Off: If your engine has a fuel shut-off valve, close it for a few minutes to stop fuel flow into the carburetor, then reopen it.
Flooded engines are a common nuisance, but by knowing these quick steps, you can save yourself time and get your small engine running smoothly again in no time!