6 Causes of a Lawn Mower Not Starting After Winter

After the season was over, you put your mower away without damaging it. Nonetheless, after the winter, the mower will not function. Mower starting issues can be exacerbated by storing it with untreated fuel or in extremely cold or wet conditions.

Old gas can restrict fuel flow in the fuel line and the carburetor, preventing the lawn mower from starting after the winter. A weak or dead battery, a dirty or corroded spark plug, or damaged electrical wiring and components can also prevent the lawn mower from starting.

When working on the mower, be sure to observe all of the safety measures outlined in the manual. The spark plug wire(s) must be disconnected prior to any maintenance being performed.

Lawn Mower
Lawn Mower

Before diagnosing, repairing, or operating, make sure you have read and understood all relevant safety information found in the equipment’s operator’s manual. If you don’t feel confident in your abilities or lack the necessary knowledge to make the repair safely, you should get some help from a professional.

Tips for Fixing and Jump-Starting Your Lawn Mower After Winter

  • If you shut off the fuel supply before putting away the mower, check to see if the shut-off valve is still open. Turn the valve to allow fuel to flow.
  • The voltage of the battery should be checked, and if it is low, the battery should be charged. You should get a new battery if the old one isn’t keeping its charge.
  • Take out the spark plug and look at it to see if it’s dirty or corroded. If there is corrosion or it is very dirty, it should be replaced.
  • Verify the fuel quality; if the fuel has been sitting in the mower over the winter without a good fuel stabilizer, it needs to be replaced. If you discover water in the fuel tank, you should change it out immediately.
  • Remove the air filter, spray carburetor cleaner into the air intake, and turn on the mower to test the fuel flow. In the event that it starts up but dies after a short while, a fuel restriction is likely to blame. Move on to examining the mower’s fuel lines, fuel pump (if present), and carburetor for any signs of obstruction.

Causes of a Dead Lawnmower in Spring

Your lawnmower won’t start due to old gas after the winter

Mowers that have been sitting in storage over the winter often develop problems due to the gas being old. Rapid decomposition of fuel is observed. As soon as 30 days after purchase, it may already be in poor condition.

Fuel ethanol is commonly used. Addition of ethanol to gasoline makes the fuel slightly less harmful to the environment. Ethanol may be better for the environment, but it won’t work in your lawnmower’s tiny motor.

Gas is necessary to keep your lawn mower operating, but it may also be the cause of your starting issue after a long winter. The fuel system can easily become clogged with condensation due to the presence of ethanol.

Because of its lower density than gasoline, the ethanol and water solution will settle to the bottom of the fuel tank. Fire cannot be started in water. Fuel flow can be restricted and fuel components damaged if this mixture is allowed to sit.

The mower won’t start if the engine isn’t getting enough fuel or if the fuel contains water.

If you find stale gas in your riding mower, you should replace it with fresh gas and drain the tank. Sea Foam Motor Treatment is a fuel additive that helps clean and remove moisture from the fuel system by adding to the gas tank.

Selecting the proper fuel and maintaining it in your lawn mower is covered in detail here.

Your lawnmower won’t start after the winter due to clogged fuel lines

Old fuel’s gummy residue can clog fuel lines and prevent fresh fuel from entering the engine. For optimal fuel delivery to the fuel pump and carburetor, you should inspect the fuel line.

Stopping the flow of fuel with the fuel shut-off nozzle or fuel pinch-off pliers will help you pinpoint the location of a clogged line. In order to collect fuel, you must disconnect the line at the end from the fuel pump inlet port (or carburetor, if your mower doesn’t have a fuel pump).

It’s important to keep in mind that fuel can’t flow uphill without the help of a fuel pump, so ensure the container is situated lower than the fuel tank.

Turn on the fuel supply and double-check how much is going through the line and into the storage tank. Reconnect the fuel line if the flow is satisfactory. If the fuel isn’t flowing smoothly, disconnect the section of line causing the problem from the mower.

Clean the line by spraying carburetor cleaner. The goal here is to break up the obstruction. The next step is to use compressed air to blow through the line and remove the blockage. It may take several attempts of spraying the line with carburetor cleaner and clearing it with air to remove the clog.

As soon as the clog is removed, the line should be reinstalled. When cleaning the fuel line proves futile or the line is cracked and likely to leak, a new section of the fuel line of the same length and diameter should be installed.

Your lawnmower won’t start after a winter’s storage due to a clogged carburetor

After leaving the fuel tank, fuel is held briefly in the carburetor’s fuel bowl. The carburetor can get gummed up and crusted over with old fuel.

When the fuel jet gets clogged or the little parts get stuck, not enough fuel gets to the engine to create combustion.

Even if fuel is flowing to the carburetor, but not the engine, the lawnmower will not start. In order to get rid of the buildup that is preventing your carburetor from working, you will need to disassemble it and clean it with carburetor cleaner.

To clean the carburetor, please refer to these instructions. A carburetor may need to be rebuilt or replaced if thorough cleaning and inspection reveal no damaged components.

Your lawn mower won’t start after winter because of a faulty spark plug

There may be issues with starting and running if you let your lawn mower sit for an extended period of time, such as the winter.

With a socket wrench, take out the spark plug and look for rust. If you notice that a spark plug is corroded, damaged, or has a very dark color, you should replace it.

A wire brush can restore an otherwise functional spark plug that has become dirty or carbonized. Spark plug gapping should be checked according to the engine manufacturer’s guidelines before installing a new or cleaned spark plug. After any necessary repairs are made, reattach the spark plug wire.

Your lawnmower won’t start due to a weak or dead battery after a long winter

You should inspect the battery in your lawnmower if it requires one to function. If you leave your lawn mower outside in the cold, the battery could freeze and become unusable. A fully charged battery will not freeze.

If it isn’t, your battery may have been damaged by the cold winter. When batteries are not fully charged, they freeze at the temperatures listed in the table below.

Battery charge12-volt batteries6-volt batteriesBattery Freezing Temperature
100%12.78 V6.39 V-80 degrees Fahrenheit
92%12.66 V6.33 V-71.3 degrees Fahrenheit
85%12.57 V6.28 V-62 degrees Fahrenheit
62%12.27 V6.13 V-16 degrees Fahrenheit
50%-10 degrees Fahrenheit
40%11.97 V5.98 V+5 degrees Fahrenheit
20%11.67 V5.84 V+19 degrees Fahrenheit
Zero charge+20 degrees Fahrenheit
Cold Weather’s Freezing Effect on Batteries in Winter

Use an ohmmeter to check the battery’s charge. A 12-volt battery is standard in lawn mowers. If the voltage of a battery is 12.7 volts or higher, it is fully charged.

If it’s lower, follow these instructions to charge the battery. If your lawn mower’s battery isn’t holding a charge, it should be swapped out for a new one.

A Guide to Winter Lawn Mower Battery Care has more information on how to maintain and store a battery.

Putting a lawnmower battery on charge

A battery charger and connecting cables are needed to charge a lawnmower’s battery. If you want to charge the battery for your lawn mower, you should do so while wearing protective gear. Here are the measures to take when charging a battery for a lawn mower:

  • Don protective gear to shield your eyes and skin from acid and electricity.
  • In order to use the battery, you need to access the terminals. To get to the battery or battery case, you may need to unscrew the lawnmower’s body.
  • The battery should be left in its case with the node cables still connected.
  • You should plug in the positive cable first when connecting the charging cables (The red one with the plus sign on it)
  • After that, you must link the negative end of the cable (The black one with the negative sign on it). Keep in mind that the positive (Red +) cable should always be plugged in first and removed last.
  • Be cautious and only let the rubberized charging cables and clamps come in contact with your skin.
  • Adjust the charger’s voltage and current to suit your needs. Lawn mowers typically operate at 12 volts. A higher amperage charging current results in a quicker battery charge (Start with two amps and work up to no more than 10 amps).
  • Keep the charger plugged in as long as the battery charging gauge indicates it needs to be. It will take about an hour for a 10 amp charger to fully charge the battery on your lawn mower.

Your lawnmower won’t start after the winter because electrical parts have corroded.

Corrosion of its components is a real risk if you store your lawn mower in an environment that isn’t clean and dry. Make sure the connections between your safety switches and your wiring are secure and free of corrosion.

Additionally, damage to electrical components can be caused by rodents. Over the winter, I have found rodent nests in lawn mowers that had been left outside. As a result of rodents taking up residence, lawnmowers frequently suffer from chewed wires and other forms of damage.

Any evidence of rodents necessitates immediate action to repair or replace affected wiring and components. The next time you need to put away your lawnmower, consider using Grandpa Gus or another rodent deterrent. This product is fantastic because it can be used in two ways: as a spray for the wiring or as a packet to place around the mower.

Frequently Asked Questions About Winter Storing

To prepare your lawn mower for the winter, should you disconnect the battery?

When putting away a lawnmower for the winter, make sure the battery is fully charged or removed.

Fully charged batteries won’t experience freezing conditions. Take the battery out if you have any doubts about its charge level or if you simply want peace of mind that it won’t freeze. Keep it in a dry, cool place out of direct sunlight and away from any sources of moisture.

Is it necessary to drain the gas from the lawn mower before putting it away for the winter?

It’s up to you to decide whether or not to empty the gas tank before putting away the mower for the season. You have the option of draining the fuel tank or leaving some fuel inside. If the latter is your preference, however, keep in mind that you’ll need to use a fuel stabilizer.

Make sure you’re using a high-quality additive that maintains the gas’s stability for an extended period of time. When it comes to fuel additives, I prefer Sea Foam Motor Treatment and STA-BIL Storage.

Caution: Only new gas will activate this stabilizer. The effects of used gas are not reversible.

Read: why I choose to use Seas Foam in my lawn mower in Use Sea Foam in a Lawn Mower to Stabilize Your Fuel.

If you want to know how to get your lawn mower ready for winter storage, here are some options:

Get rid of the gas in the lawn mower before putting it away for the season.

Empty the fuel tank into a fuel-safe container using a fuel siphon pump. Start your lawnmower and let it run until the engine dies from a lack of gas. In this way, we can drain the fuel system of its contents.

Don’t just leave gas in the tank over the winter; stabilize it first.

In order to properly blend new gasoline, add a fuel stabilizer as directed on the bottle. Place it in the gas tank.

After adding the stabilizer to the fuel and starting the mower, let it run for a few minutes to ensure the fuel has been thoroughly circulated.

Is Your Lawnmower Still Giving You Trouble?

Owning a lawnmower isn’t without its challenges. If you keep a lawn mower for a long enough period of time, you will inevitably run into issues with starting, smoking, leaking, cutting, and overheating.

Check out my guide “Common Lawn Mower Problems: Solved!” for a rundown of the most common issues with lawn mowers and the possible solutions.