Starting a Lawn Mower with Old Gas

Tips for Starting a Lawn Mower with Old Gas

When you think of things that get old and start to go bad, you tend to think about food products. One thing that probably does not come to mind is gasoline. But over time gas breaks down, and when left in machinery such as lawn mowers it can cause reduced performance or even difficulty starting. If you have old gas in your lawn mower, don’t fret. Here are some tips for starting a lawn mower with old gas that will get your mower out of the garage and purring like a kitten this Spring.

Trust and Accuracy Information

This article was last updated on by Lawn Chick Owner Sarah Jameson
Article content reviewed for accuracy by Horticulturist Arthur Davidson, A.S.

Clean out your lawn mowers gas tank.

While it is highly recommended that you drain the gas from your lawn mower before letting it sit for long periods of time, not many people don’t know this (which is probably why you’re reading this post).

When gas sits in your law mover it will break down and cause residue build-up. Refer to your lawn mower’s manual for service procedures and information on how to remove the build-up from the fuel tank.

And if you don’t want to face this problem again next Spring, read and follow my lawn mower winterization guide this coming fall.

Remove the Remaining Gas from the Tank.

Once the build-up is gone, siphon out the old gasoline and put it in a container for proper disposal.

This is done by running a siphon hose from the gas tank to a container and pumping the bulb multiple times. By pumping the bulb, you are pulling the gas out of the fuel tank and draining it into the new container, therefore cleaning out your lawn mower.

Adding new gas to the fuel tank should prime your mower’s fuel tank make your lawn mower run like new.

Check the Spark Plug

If you have already cleaned out the tank and added new, fresh gasoline to your lawn mower and it still won’t start after sitting, be sure to check the spark plug.

When you store your lawn mower for long periods of time, there is a significant possibility that your spark plug wire may come loose, so be sure to check that, and make certain it’s pushed all the way in.

Tips for Starting a Lawn Mower with Old Gas
Your lawn mower’s spark plug cable will usually be on the front of your walk-behind mower.

After doing this, try starting your lawn mower again.

And while we’re on the subject of spark plugs – you should replace your mower’s spark plug every other year. It’s cheap (under $10), and just takes a few minutes.

Don’t Flood the Carburetor

A common mistake when trying to restart your lawn mower after not using it is flooding the carburetor.

When trying to start your lawn mower, be sure to note the sounds and smells it is creating. Stop trying to restart the mower when the smell of gas becomes strong.

A strong gas smell means a flooded carburetor.

Wait a few minutes before trying to start the mower again.

Starting a Lawn Mower with Old Gas is Easy with TruFuel

Starting a Mower with Old Gas

Because I’m the Lawn Chick and my mower deserves nothing but the best, I run a product called TruFuel in my mower.

It’s good old-fashioned gasoline that is ethanol-free.

This gas is more expensive, but I can leave it in my mower all winter and every spring my Honda starts right up on the first pull. I use it in my snow blower as well, and I’ve never had to have either machine professionally serviced. I highly recommend it. You can pick it up on Amazon, and most box stores and local hardware stores carry it as well.

Ensure Proper Maintenance Before Putting Your Mower Away

You can treat your gas to winterize it, or you can use the more expensive product I mentioned above, but the easiest way to ensure your lawn mower will start after a long winter is to simply drain the old gas out of the fuel tank before you put it away.

Clean the moving parts of your lawn mowers engine and make sure the spark plug wire is pushed in. Use a can of starting fluid as a last resort.

There is nothing more satisfying than bringing your lawn mower out of storage, having it start right up and deliver the sacred smell of fresh-cut grass.

Be prepared for that time of the year and take care of your lawn mower.

At Lawn Chick, I am committed to publishing accurate, useful, and trustworthy resources for my readers. As part of this commitment, I’ve invited subject matter experts to review our articles for accuracy. I invite you to read our editorial policy and publishing standards which outlines in detail how every article on this site is sourced, edited, fact-checked, and vetted.



Sarah Jameson’s blog, Lawn Chick, is read by over 2 million homeowners each year and she is regularly cited as an expert source of lawn care knowledge by major publications. Her goal is to meet you where you are, and help you achieve a yard you’ll be proud of. Ready to take the next step toward improving your lawn? Grab her free lawn care cheat-sheet: What to Do When - Take the Guesswork Out of Lawn Care, or upgrade your garage by browsing her favorite DIY lawn care products.

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