If you forgot to winterize lawn mower and now it won’t work properly, there are some remedies you can try to save your mower. Who hasn’t been lazy for a year or two when we just put our lawnmowers away without emptying their fuel tanks and cleaning them properly first?

Forgot to Winterize Lawn Mower

In this complete guide, our team has compiled all the possible negative consequences that could occur because of this unfortunate oversight.

You will also discover what you need to do to bring your mower back to life again. 

What Happens if You Forgot to Winterize Your Lawn Mower?

If you forgot to winterize your lawn mower before being stored for the winter, it will fail to work properly in the upcoming spring season. What happens is that the fuel in the gas tank goes bad and causes corrosion and blockage of engine parts.

Other effects of not winterizing your lawn mower include the spark plug becoming damaged, debris building up in the carburetor and causing a blockage, the battery wearing out, and heavy corrosion occurring in the mower. Here are some more effects that are caused by not winterizing lawn mowers.

– The Gas Goes Bad

Removing gas from the fuel tank is an important part of winterizing a lawn mower. Otherwise, the gas goes bad over the winter months and ends up being harmful instead. This is especially true if a fuel stabilizer is not added to the gas to make it last through the winter.

The gas goes stale and breaks down into harmful components. Not only is stale gas no longer able to fuel the engines working, but its breakdown products will cause blockage and harm to different parts of the mower engine. Most gasses break down into a gum-like sticky residue that blocks the engine parts and is difficult to clean. 

– The Spark Plug Might Die

A spark plug is one of the central components of your lawn mower’s engine machinery. Unfortunately, certain older designs of spark plugs can be susceptible to cold and get damaged if not winterized properly. Moreover, if you have left the mower at the mercy of cold winds, rain, and snow, the spark plug will be the first to get corroded.

It is quite straightforward to see when the problem lies with your spark plug. Either the engine will not start to begin with, or it will start but the mower will fail to turn. Read your mower’s instructions manual to see where the spark plug is located and then inspect it. 

In most mowers, the spark plug is located either on the back of the machine or its sides. It is a slight protrusion from the mower’s body, and you will have to unscrew its protective cover to gain access to it. In some cases, the spark plug needs a good cleaning, but in the worst-case scenario, you will have to replace it altogether.

Results of Forgotting Winterize Lawn Mower

– Debris Will Build Up in the Carburetor

As a consequence of not properly emptying the fuel tank before storing the mower for the winter, you will have to deal with a clogged carburetor later. The fuel breaks down, and its constituent products end up as grease and other glue-like substances that block the engine’s carburetor and other tiny passageways.

The carburetor is located within the engine, just behind the air filter. Most modern lawnmowers’ air filter is towards the machine’s side. It is covered by a meshwork protective covering that needs to be unscrewed. After removing the air filter, you can access the carburetor and see how completely covered in black junk it is.

– The Battery Wears Out

Most of us do not use our lawnmowers from the end of autumn through winter until the beginning of spring. The battery is at risk during all these long and cold months of no use. First, forgetting to take it out might cause the battery to be fully exposed to the cold winter.

The battery fluids freeze over and expand, damaging delicate parts in the process. Secondly, if the battery is not stored properly and is exposed to moist air or snow, this would cause its various parts to corrode and stop working.

Even when the battery was taken out before winter and stored properly, it would still lose its charge, and you will have to recharge it all day before it can be used again. 

– Corrosion Might Occur

Your mower is at risk of getting its parts corroded from gaseous breakdown over the winter. Corrosion is more severe when poor-quality gas containing ethanol is used. Over time, ethanol absorbs moisture from the air and then corrodes the fuel tank, the carburetor, the pipes of the machinery, etc. 

Corrosion is unhealthy for the machine because while some parts can be cleaned and replaced easily, others are much trickier. Hazardous gas and oil used as lawn mower fuel is something we would never recommend. 


How Do You Fix a Mower That Has Not Been Winterized?

To fix a mower that has not been winterized and is now faulty, it is important to clean its fuel tank and add fuel to it that is clean and stabilized. It is also important to clean residue from other components, such as the air filter and the carburetor. 

The spark plug should also be fixed if it has become faulty, and the lawn mower vent should be cleaned. It would be wise to add a fuel stabilizer to the fuel for future winter seasons.

– Clean the Air Filter First

The carburetor is usually accessible from the outside via an air filter. This filter and the carburetor must be cleaned first so the mower can start working properly again.

Fix a Mower That Has Not Been Winterized

Technically, the air filter must be cleaned after a mowing usage of roughly 25 hours, but since yours has been lying in dust all winter, it needs to be cleaned before the mower is used again.

  • Before you can even go near the air filter, you must ensure that the mower engine has been turned off and that the key is out. 
  • Loosen the screws holding the filter’s protective covering in place. Once the outer covering has been removed, carefully take the air filter out. 
  • Your air filter will be made of either foam or paper, so you must check if it can be salvaged. Hold the paper filter upto a lightbulb and discard it if it seems to block most of the light. If not, then go ahead and tap it on a table to get the dust off.
  • On the other hand, you must discard the foam type of air filter when it becomes completely black and deformed. Otherwise, soak it in a water and soap solution for 15 minutes to remove all the accumulated dirt. 

Only reinstall the filter back when it becomes 100 percent dry. While you have the air filter opened up, you should take the carburetor out and clean it as well.

– Clean the Carburetor Next

To clean the carburetor, you must detach all of the links connecting it to the engine. Put on your thickest pair of rubber gloves and disconnect the cables that connect the carburetor to the throttle and choke. Use a screwdriver to loosen the few bolts that hold the carburetor attached to the engine.

Disconnect the fuel line and keep a bottle ready to collect the fuel that will eventually drip. Finally, before disassembling the whole assembly, it is safe to take a picture. This way, you can always refer to how everything is supposed to look once you start reassembling everything.

Some carburetor parts, like a gasket, need to be replaced more often than others. If there is significant damage on any other parts, then those need to be replaced by newer ones. As for the rest of the carburetor parts, clean all of them using a toothbrush and a soap solution. Let everything air dry throughout its time, and then reassemble it. 

You can also purchase a special carburetor cleaning commercial solution if you like. Have all the tiny parts soak in this solution for about an hour before you wash them with clean water. With a professional cleaning solution, there is little risk of corrosion occurring on the metal parts. 

– Fix the Faulty Spark Plug

The spark plug is one delicate part of your lawn mower’s machinery. It is not surprising to see it not working after you fail to winterize the mower for a long period of time. Either the engine will fail to start from the get-go or will die soon after starting.

  • The front of the mower is the most probable location where a spark plug might be located. Before you touch it, double-check that the engine has been turned off. You want to avoid electrocuting yourself accidentally while fixing the spark plug.
  • A wrench can disconnect the spark plug from the mower body. It will most likely be coated in greasy residue from fuel breakdown. Sometimes, the spark plug even appears corroded after a long time of unuse. 
  • You cannot soak the spark plug in soapy water for any time whatsoever. Just spray a little brake grease cleaner on the greasy parts and let it stay there for 20 to 25 minutes before wiping it off using a clean cloth. 
  • Once the plug dries completely, put it back in its place and secure the bolts carefully using a wrench. 

– Clean the Lawn Mower Vent

Sometimes, we take the mower out after months of not winterizing it and it seems to start just fine. However, it then sputters and comes to a halt soon afterward. In this particular scenario, the most probable cause is a fuel vent that has become defective.

The vent within the fuel cap of the engine is responsible for the flow of fresh gas from the fuel tank to the carburetor. The gas builds up within the tank when the vent becomes clogged by fuel breakdown products. Consequently, the engine starts alright but stops as the fuel flow is disrupted.

Most of the time, just detaching the fuel cap and reattaching it fixes the vent. Otherwise, you might have to clean the residue off it by soaking it in soapy water for 15 to 20 minutes. If the problem persists even after this, you will have to replace the old lawn mower vent with a new one. 

– Clean the Fuel Tank and Refill It

One of the biggest disservices we commit by not winterizing our lawnmowers is towards the fuel tank.

This is where most of the gas breaks down into toxic and congealing by-products. This tank needs to be rid of the old fuel and cleaned from all the dirt and debris before you can refill it with fresh gas.

  • Take all the safety precautions by wearing gloves and goggles, turning the mower engine off, and disconnecting the spark plug. As always, never smoke while working with gasses or oils nearby. 
  • If you have a siphon drain, drain the old fuel from the tank. Otherwise, disconnect the gas line that attaches the carburetor to the tank and place a container underneath. Collect the spilling fuel from the gas line into this container and store it for the time being.
  • You cannot use any water-based cleaning solution to clean the insides of a fuel tank. It would help if you bought a special oil-based cleaning solution for this procedure. Pour it onto the tank, close it off and shake the mower so it reaches every nook and corner.
  • After 5 to 10 minutes, drain the cleaning solution and refill the fuel tank with brand-new fuel. 

– Add a Fuel Stabilizer to the Fuel

It’s okay to avoid winterizing lawnmowers by emptying their fuel tanks. Make sure you are using the best possible quality of gas and oil available in the market.

treatment a Mower That Has Not Been Winterized

Lawn mower fuel needs to be high-octane, ethanol-free, and have fuel stabilizer added to it. Such a fuel will last at least six months within the tank without going bad and will also tolerate colder-than-average temperatures. 


Let us summarize the important points discussed in this article about forgetting to winterize your lawn mower.

  • Winterizing a lawn mower means you empty its fuel tank, clean its parts such as mower blades, and keep it in a temperature-regulated place.
  • If mowers are not winterized for the season, the old gas and oil will go bad and deposit sticky residue everywhere.
  • The mower parts will need extensive cleanup before the machine can cut grass again.
  • Using premium-quality fuel with a fuel stabilizer containing zero percent ethanol will prevent many of these problems.

The next time you take your mower out of the tool shed after several months of being unused, do not be shocked when it refuses to start. Go through all the hacks discussed in this article and get your machine back on its feet immediately!

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