How to Start a Flooded Lawn Mower – The Lawn Mower Guru (2024)

Last Updated: June 20, 2023 By Guru

Most people that own a lawn mower will experience flooding their engine at one point or another. Your mower won’t start, which is kind of a problem. But does it mean that it’s now useless? Is it a costly repair? And will you have to cut your lawn by hand in the meantime?

We’re going to answer these questions, plus explain how to start a flooded lawn mower in this post.

How to Start a Flooded Lawn Mower (The Short Answer)

If you suspect that your engine is flooded and you’re unable to start your lawn mower, here are two methods you can use to get your mower engine fired up again.

Option 1:

• Remove the spark plug
• Allow gasoline to evaporate

Option 2:

• Remove the spark plug
• Dry the spark plug.
• Crank the engine a few time,
• Reinstall the spark plug
• Clean the air filter

How Do You Tell If Your Lawn Mower is Flooded?

First things first. Are you absolutely sure that your mower is flooded? There are a whole bunch of reasons why it might not be starting, so before you take any action, it’s a good idea to try and find the cause.

Here’s how to tell if your lawn mower is flooded:

Remove the Spark Plug and Smell It

This is a very quick way and my go-to method for determining whether you’re dealing with a flooded mower engine. Simply remove the spark plug and smell it. Does it reek of gasoline? If so, your engine is flooded, and you’ll need to follow the steps below to learn how to start your mower up.

You Smell Gas When Trying to Start Your Mower

You might not even need to do the test I just described. If you’ve been trying in vain to start your mower, but it’s not playing ball, and you notice a potent gasoline smell, I’d put money on your engine being flooded.

Why Can’t Your Lawn Mower Start If It’s Flooded?

I won’t ramble on too much here, but it’s interesting and perhaps useful to understand exactly why a flooded lawn mower can’t start.

So your mower’s engine consists of various parts. There’s a carburetor (which mixes gas and air that enters through the air filter), pistons (which draw in the gas and air mixture and compresses it), and a spark plug which provides a tiny spark, leading to the combustion that provides the energy to drive your mower.

The air-fuel ratio needs to be just right for this process to take place, and when the engine is flooded this ratio is thrown out of whack. Basically, there’s too much gas and not enough air. And your start mower isn’t able to start.

Lesson over. Now let’s run through how to unflood a lawn mower.

How to Start a Flooded Lawn Mower: Your Options

There are basically two approaches you can take. Which one you want to take will really depend on how much of a rush you’re in. That’ll make sense in just a minute.

Wait for the Fuel to Evaporate

The first solution is really very simple. You just wait. That’s it. No magic trick here. You just set your mower on a level surface and wait 15-20 minutes for the fuel to evaporate and then there’s a strong possibility that the mower will start up.

It’s rarely the case when it comes to lawn mower repair and maintenance, but a flooded mower can actually fix itself, in a way. Pretty cool if you have the time. (and great for lazy folks like me!)

The More Involved, But Faster Method

Don’t have 20 minutes to sit, twiddling your fingers while the problem takes care of itself? No worries as there is a faster way to start a flooded mower. Here’s how to do it.

You’ll need a few supplies:

Spark plug wrench
Starter fluid
Dry cloth
Screwdriver

Then here’s what you’re going to need to do:

• Remove the spark plug connector and unscrew the spark plug with your spark plug wrench. As I mentioned earlier, the terminals will be soaked with gas. You’re going to need to dry them. You do this by spraying an alcohol-based starter fluid onto it, or by wiping it with a clean, dry cloth.
• While you still have the spark plug off, crank the engine a few times. Make sure you stand back while you do this, away from the front side of the engine. This will draw air through the carburetor to help dry the engine out.
• Now replace the spark plug, turn off the choke and crank the engine. If it sputters, crank it a few more times until it starts. Sometimes you’ll need to turn the choke on to get the engine to turn over, but you should turn it off again immediately as the engine starts.
• If the engine doesn’t sputter and still doesn’t want to turn over, you might want to remove the air filter. This is where the screwdriver comes in handy – you may need to use it to remove a screw to get to the filter.
• Give the filter a good clean, put it back in place and immediately start the engine up. If there is no response, remove the filter and leave it off while you crank the engine a few more times to empty the carburetor. If the engine sputters or turns over while the air filter is off, the filter is dirty and should be replaced. Sometimes, with a flooded mower, the mower’s air filter may get soaked with oil. It will be very apparent if this is the case, and most of the time the only option will be to replace this (sometimes the foam ones can be washed, but oil is often a devil to get off).

Things to Be Careful of When Fixing a Flooded Lawn Mower

Even though getting a flooded lawn mower started again is a fairly easy process, there are a few things you will want to be careful of. Let’s take a look.

• Be cautious when working with gasoline.
• Be aware that when cranking a lawn mower engine without a spark plug, fuel will be ejected from the engine.
• Make sure to completely remove the spark plug from the lawn mower, as cranking an engine without the spark plug grounded will result in spark plug damage.
• Ensure that when you clean your lawn mower air filter, you use an appropriate method.