My Lawn Mower Won’t Start After Winter – What Could It Be?

As the winter season gradually fades away and spring buds into full bloom, many homeowners prepare to bring their lawnmowers back into service. However, if you’re experiencing difficulty starting your mower after a long break, you’re not alone. 

Common reasons for the starting problems include stale fuel, corrosion, clogged air filters, carburetor issues, or any combination of these. With some simple troubleshooting and a little maintenance, many of these issues can be easily fixed. 

In this article, I’ll cover the common reasons why your lawn mower may not start and provide you with detailed instructions on how to address each issue. Additionally, I will offer some tips for maintaining your lawn mower during the off-season, so you can prevent future starting problems. So, let’s get started and get your lawnmower back in action! 

Stale Fuel – The Most Common Cause Of A Mower Not Starting After Winter

One of the leading causes of difficulty starting your lawnmower after winter is stale fuel. Gasoline can go off when it has been sitting unused for an extended period, causing it to lose its volatility. 

Signs of stale gas include a mower that will not start or initially runs fine but then the engine sputters and stalls.

To fix this, you will need to use a siphon to remove any old gasoline from the fuel tank or pull the fuel line where it enters the carburetor. Be sure to empty this into a container that can safely store gasoline and then dispose of it properly.

After removing the stale fuel, refill the tank with fresh gasoline. Use gas that contains a stabilizer if you do not plan to use your mower often.  This will stop your fuel from going off when being stored and often helps keep your engine components clean in the process.

You can also add a fuel stabilizer whenever you refill the fuel tank to keep it topped up.

Cleaning A Clogged Carburetor

Another common cause of difficulty starting your lawnmower after winter is a clogged carburetor. Similar to having stale fuel (and this is often the cause of a clogged carburetor), you may notice that the engine turns over, but it fails to start or runs for just a few seconds before stalling. 

To clean the carburetor, start by removing its cover and the air filter. Next, locate the carburetor’s bowl and remove it. Take out the carburetor’s float and place it on a level surface. 

Use a carburetor cleaner to clean any dirt or debris inside.  Also, spray the cleaner into all of the carburetor’s tiny holes, such as in the jets, to remove any obstructions. Allow it to dry before reassembling. 

I know this sounds a bit too complicated to most people, but here is a great video that shows you how it’s done: 

To prevent the carburetor from gumming up, always use fresh stabilized fuel and before storing the mower over winter, run it for a few minutes to ensure that the fresh stabilized gasoline circulates throughout the whole system.

Does Your Riding Mower Have A Dead Battery?

If your mower has an electric starter, such as on a riding mower, a dead battery may be the problem. If you notice that the engine is turning over slowly, or the mower’s headlights are dimming when it is on, it indicates that the battery charge is low. 

To jump-start the battery, connect a set of jumper cables from a charged car battery to the mower’s battery. Now, it is important to do this properly. If you are not sure how to do it, check out this article where I cover this topic in greater detail. 

Keep your lawnmower’s battery charged during the colder months by running the engine for a few minutes every few weeks or connecting it to a battery charger.

Dealing With Spark Plug Issues

Another issue that may prevent your lawnmower from starting is a bad spark plug. Sometimes these can become corroded over the winter and this will result in an engine that refuses to fire or runs roughly.

To replace the spark plug, locate its position on the engine and use a spark plug wrench to unscrew it from the socket. Examine its condition, and if damaged or worn, replace it with a new one that meets your mower’s requirements.  

If it just has some light corrosion then clean it off with a wire brush and check that the electrode gap is within the manufacturer’s guidelines before putting it back in and trying to start the engine again.

Keep in mind that if you tried to turn your mower on recently, the spark plug could still be hot and you could easily burn your hands if you touch it without protective gloves (it happened to me more times than I can count, so be careful…). 

To prevent further problems store your lawnmower under cover during winter to prevent moisture buildup in the spark plug well. If you are storing your mower outside, here are a few tips you can follow to keep accidents like this from happening.

Clean Or Replace The Air Filter

A dirty air filter that cannot supply enough air to the engine may be another reason you are having difficulty starting the lawnmower or keeping the engine running.

To clean the air filter, remove it from the engine, and wash it using soap and water. Dry it thoroughly in a warm place and then reinstall it on the mower. Note that if the filter has missing, broken, or ripped parts, you might need to think about replacing it. 

Here is a video that shows you how it’s done: 

Final Thoughts

I hope you’ve found my post useful and that you now know how to troubleshoot a lawnmower that refuses to start after winter. Just to recap, I recommend that you start by checking if your gasoline has gone stale, then go through checking for a blocked carburetor, faulty spark plug, dirty air filter, or a dead battery. 

To avoid problems in the future store your lawnmower in a dry place over the winter and make sure you have added stabilizer to the fuel system so that you don’t have to drain it. Note that if your storage space is in your house or basement, always drain the gasoline to prevent a fire risk.

By regularly maintaining your mower you can usually avoid starting problems in the spring. But if it does give you trouble, these tips should get your mower running again in no time!

Peter Toth

Hi! I'm Peter, the owner of BackyardGadget. Working around the house has always been a big part of my life. I've created this site to share my experience, and to help people choose the right tools for the job. Thank you for stopping by!

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