It happens fast. One minute your lawn mower won’t start, and the next you’re pulling the starter rope again and again, getting nowhere. If you start to smell gasoline and the engine just won’t catch, chances are it’s flooded. Don’t worry—it’s not broken. This is a common issue, and with a little patience and a few easy steps, you’ll be back to mowing your yard in no time, lucky you.

What Causes a Lawn Mower to Flood?

Flooding issues happen when too much fuel enters the engine ignition chamber before it can ignite. This can happen to any garden equipment if you press the primer bulb too many times, choke the engine for too long, or try to start it over and over without success. The extra gas floods the spark plug, which then can’t create sufficient spark needed to start the engine. You may also notice a strong fuel smell, or even see gas dripping from the carburetor.

This doesn’t mean anything is broken or major damage. It just means the engine is soaked with too much fuel. Fixing it is mostly about clearing that out.

Flooded yard with puddles in the grass.
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How to Fix a Flooded Lawn Mower

The first thing to do is stop pulling the cord. Every time you do, you’re likely adding more gas to the problem. Here’s what to do instead:

  • Wait about 15 minutes. This gives the extra fuel time to evaporate.
  • Move the mower to a shaded, open area with good airflow.
  • Set the choke position to the “off” or “run” position.
  • If your mower has a throttle, set it to the highest setting.
  • Try pulling the starter cord again—just a couple of times.

If that doesn’t work, you might need to remove and clean/dry the spark plug. Here’s how:

  • Disconnect the spark plug wire.
  • Use a socket wrench to remove the spark plug.
  • Check if it’s wet with fuel. If it is, dry it off with a clean rag or let it air dry for 10-15 minutes, or blow it off with an air compressor. Use the air nozzle to blow out the spark plug hole too.
  • Reinstall the plug and reconnect the wire. Once dry, the spark plug should fire up the engine on the next try.
One of two spark plugs on a riding lawn mower.
Checking the spark plug can sometimes fix the issue. Credit: Emily Fazio

When Waiting Isn’t Enough

Sometimes, waiting and drying the plug isn’t enough. If your lawn mower still won’t start, it could mean gas has filled other parts of the engine. In that case, try these extra steps:

  • Remove the engine air filter and check if it's wet with gas. If it is, let it dry or replace it.
  • Tilt the mower (spark plug side up) to help drain excess fuel.
  • Gently pull the starter cord a few times with the spark plug removed. This helps push out extra gas.
  • Check the engine oil. If it smells like gas or looks thin, it may need to be replaced with clean engine oil before restarting.

Still stuck? It might be carburetor time. Flooding can sometimes cause gas to collect there too. If you’re comfortable, remove the bowl under the carb and look for excess fuel. If that’s not your thing, a local engine repair shop can help.

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Preventing Flooding in the Future

Once you’ve had a flooding issue with your engine, you’ll probably want to avoid it next time. Here are a few simple habits to help keep your mower starting on the first try:

  • Make sure you're following the proper starting procedure.
  • Don’t press the primer bulb more than 2-3 times.
  • Use the choke lever briefly—just to get it started—then turn it off.
  • Give the engine a few seconds between starting attempts.
  • Keep your spark plug clean and check it each season.
  • Store your mower properly at the end of the season to prevent gumming or buildup.