How To Start A Lawn Mower That's Been Sitting For A While?

Written By James
Updated May 1, 2022 by James

How To Start A Lawn Mower That's Been Sitting For A While?

Our Guide To Starting A Mower Which Has Been Sitting

Whether you've got your hands on a passed down lawnmower that hasn't been used in years or your lawnmower has been sitting in storage for a long time after winter without regular maintenance, you might be faced with a mower that refuses to start. 

Starting a mower that's been sitting for a while can be difficult, especially if the lawnmower engine was not stored correctly and old fuel was left inside, luckily, you can remedy a mower that won't start by using tricks and tips such as priming the mower and draining old fuels. 

So as you can figure out how to troubleshoot your mower properly and get it up and working again, we have composed an informational guide below, that will tell you how to identify any issues in your sitting mower, the best way to start the mower and how to store it correctly next time. 

Let's get into it!

Why Is My Lawnmower Not Working After Being In Storage? 

When any model of mower has been sitting for a long time, many problems can occur, for battery-powered lawnmower models, this could be that the battery has become flat, and for a petrol model mower, if they were stored in high humidity, condensation could have potentially formed in the fuel tank. 

There are many ways you can prevent these issues from happening, such as by draining excess fuel or adding a fuel stabilizer to your mower, but from time to time, issues will still occur, especially if you are trying to restart a 3-year old mower that has been hardly used. 

If the carburettor of your lawnmower is not working then your mower will not start and the spark plugs will not work, so there is a high chance if your lawnmower is struggling to start after being in storage, it's down to the carb engine or an issue in the fuel tank. 

So in a summary, the following reasons could be the culprit as to why your faulty mower is not starting after storage - 

  • Fuel tank. 
  • Carburettor. 
  • Oil. 
  • Spark plug. 
  • Flywheel key. 
  • Air filter. 

We will get into how to troubleshoot these different parts and fix them below to try and restart your lawnmower. 

Our Troubleshooting Guide To Start Your Mower 800

From a dirty carb to a blocked air filter, there are a few different components of your lawnmower to look at before throwing your mower away, all of which can be fixed to get your mower going. 

We have listed the most common problems that happen when a mower has been sitting for too long below and how to fix them.

Check & Change Gas

The gasoline which is in your lawnmower is one of the first things you should check if your mower is not starting after sitting, fuel in a gas tank can start to go bad after just 30 days, so if your larger mower still has old fuel in it, this could well be the problem. 


To fix these bad fuel issues, simply tip the mower and get rid of the old fuel then replace it with gasoline fresh and add a fuel stabilizer so as you can extend its lifespan, if your fuel is not easy to drain then use a siphon hose to do this instead. 

Change The Oil 

Next, you should change the oil that is in your mower, this is done normally during mower maintenance, so if your oil has been sitting for a long time, it most definitely will need to be changed. 

If your oil in your mower looks black or discoloured, then you will need to replace it, a smoking mower can also be a sign there is an oil leak that needs to be fixed, although this might not be stopping your mower from starting. 


Changing the oil in your walk-behind mower will be quick and easy, just simply undo the oil drain plug and pour the old oil into a container, try not to spill it anywhere on the ground. This should be done once or twice a year normally depending on how much you use your lawnmower. 

Replace The Air Filter 

Along with old fuel, a dirty air filter that has been clogged over time can stop your mower from functioning how it should, as it restricts the oxygen from reaching the fuel tank, meaning the mower won't start as it doesn't have the fuel to air ratio it requires for combustion. 

If your mower has been sitting for a while it's best to just replace the whole air filter rather than try and clean it. 


Either clean the foam filter around your mower's engine or change it, paper filters cannot be cleaned, so swapping it out for a new one won't hurt and is easy to do, as well as inexpensive. If you decide to clean your foam filter pre part, make sure not to blow any debris further up into the engine.

Get a New Spark Plug 

For standard lawnmower repair, you should blame the spark plug next if the above is not making a difference. Check the condition of the spark plug wire and see if it is damaged, as no spark means no start! 

If the wire looks fine, disassemble to plug itself and inspect for corrosion, clean and reinsert. 


It might be best to just replace your spark plug on your old mower which doesn't cost too much and is simple to do. Find the right-sized wrench to disconnect the old spark wire and reattach the new black wire, always disconnect this again when you are doing other lawnmower expert repair. 

Tighten The Brake 

Pull the brake cable on your lawnmower and get a feel for the tension, if the brake cable is loose then the mower tool will not start no matter what you do! You can check this by pulling the brake tight and trying to start the mower at the same time, if it starts then this is the cable to blame. 


Grab your right-sized crescent wrench and vice grips and give the brake a tighten, this should be a simple process you can follow from your mowers manual and shouldn't take too long. A loose brake cable is quite likely if your mower has been passed down to you and was sitting around.

Is The Carburetor Dirty?

The carburettor over time can become dirty with debris and blockages, a dirty carburettor often happens when gasoline-powered tools have been left with old fuel as we mentioned above, so if you left fuel in your mower, a dirty carb is common. 


To clean a dirty carburettor you can use vinegar or carburettor spray to clean the carburettor bowl, however, you might need to take it to a professional if you believe it needs to be removed and cleaned properly. You might need to replace the whole carb if it is damaged in some cases which should be fitted by a professional.

The Flywheel Key Might Be Broken

A broken flywheel key from debris hitting it can be a reason for your mower not to start working, this is what spins when you pull the starter cord on your walk-behind mower, so if the last person who used the mower damaged the flywheel before storage, that's why it's probably not starting. 


Broken flywheels can be hard to fix on your lawnmower as a beginner so you might need to take it to a professional to be checked in this case, if you break the blades of the wheel, they can be expensive to replace, so avoid DIY'ing this if your not mower savvy with repairs. 

A Problem With The Fuel Pump 

Now, lastly, you might have a fuel pump defective part, excess oil can leak into the fuel valve of your pump damaging its ports and stopping your mower's engine from starting as fuel cannot be pumped to the engine. 


To fix this, we recommend taking it to a professional, but no matter what you will need to replace the whole fuel pump as these parts can unfortunately not be repaired, but aren't too costly to get your mower back up and running. 

The Best Method For Starting Your Sitting Mower 

After troubleshooting all of the above, you might want to start up your sitting mower for the first time, and when doing this, there are a few tips and tricks you can do to try and encourage your dormant mower to start up again, we will list the steps below. 

  • Step One - Prime your lawnmower's engine by pressing the prime button near the carb at least three times, then turn on the choke and try to start the engine, do this a few times before stopping. 
  • Step Two - Put the throttle on your mower into a fast position and your foot on the mower while you give the starter cord a good pull, if you smell gas coming from the mower, stop and start again in 5 minutes as the carb could be flooding. 
  • Step Three - Press the primer button a few more times and try to start the mower, pull the throttle to a slow position if it manages to start back up again. 
  • Step Four - If you notice the spark plug wire is torn, try pushing it on as you start the mower. 
  • Step Five - When the mower turns back on let it run for around five minutes so as the fuel can circulate properly. 

Tips For Storing Your Lawnmower Correctly 

So as you can avoid all of the above hassles next time, we recommend storing your mower correctly with a few tips, this will allow you to take your mower out after winter or long storage and use it straight away with no issues. 

  • Remove old fuel - As we mentioned above, having old fuel sitting around in your lawnmower is a big no-no, you can solve this by draining it entirely before storage or adding a stabiliser so as it can last for longer and not condensate inside of the mower.
  • Take off the battery - Electric mowers will need the battery removed for storage over long periods, storing your battery in cold temperature within a shed can damage it. 
  • Change the spark plugs - Removing the spark plug and changing it can be done before storing your mower or even after, check the original for any damage and decide whether or not it is necessary.
  • Drain oil - Drain the oil in your mower to remove any debris that can sit and replace it with fresh ready for its next use.
  • Clean it well - Moisture left by old grass clippings and other dirt can corrode and cause rust on the blades of your lawnmower.
  • Check the air filter - A dirty air filter can be changed quickly before storage and will make it simpler for you when you re-surface your mower, paper filters are easy and cheap to replace.
  • Store it upright - Old fuel and oil can drip if you store your lawnmower on its side, so always store it upright unless your manufacturer suggests otherwise.

Frequently Asked Questions About Starting a Lawnmower That's Been Sitting 

How often should I be maintaining my mower and checking its parts? 

There is no maintenance rule for lawn mowers as the times for checking the engine will depend on how often you use it, this could be after 20-50 hours of use, but parts such as the oil level might need checking soon after maybe 5 hours after use. 

Most people tend to give their mower a check at least twice a season to make sure everything is working how it should be.

When should I change the oil in my lawnmower? 

Changing and replacing the oil should be done between 20-50 hours of operation, the oil will start to look black and discoloured when replacement is needed.

How much does a new carburettor cost for a lawnmower?

A new carburettor for your lawnmower can cost anything between £30-£50 for your lawn mower engine. 

Final Words 

To conclude, if your mower has been sitting for a while and will not start then you should always check the fuel, spark plug and air filter first, then dive deeper and troubleshoot other components.

Remember, if you are planning to store your mower for long periods do so correctly to save the hassle next time you take it out by following our tips and advice above.

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My father, and his father before him, and his father; for the past 3 generations, my family have always been into gardening. The green fingers is a gift passed down to me and I thoroughly enjoy it! I also have worked in the manufacturing department for Bosch and DeWalt so I like to think I know a thing or two about tools and such!
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