FIXED! Riding Mower Won’t Start After Winter

Warm weather is finally here. It’s time to get your riding mower out of storage after the long winter season. You cross your fingers and hope your mower will start right up after being stored for so long. What do you do when it doesn’t start?

A riding mower may not start after winter when old gas corrodes the fuel system and restricts fuel flow with clogs in the fuel lines or a dirty carburetor. A bad spark plug, dead battery, and corroded electrical components and wires can also prevent a riding mower from starting after winter storage.

When working on your riding mower, follow all safety instructions provided by the manufacturer. This includes protecting your hands, skin, and eyes when working with the battery, fuel, and electrical system.

Common Reasons a Riding Mower Won’t Start After Winter:

  • Old gas
  • Clogged fuel lines
  • Dirty carburetor
  • Bad spark plug
  • Bad or dead battery
  • Corroded fuel components
Riding mower won't start after winter

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Follow all safety instructions provided in your equipment operator’s manual prior to diagnosing, repairing, or operating.Consult a professional if you don’t have the skills, or knowledge or are not in the condition to perform the repair safely.

Reasons a Riding Mower Won’t Start After Winter

Old Gas Keeps Your Riding Mower from Starting After Winter

While gas is required for your riding lawn mower to run, it can also be the root cause of your starting problem. Fuel, over time, will break down becoming less effective, leaving a sticky substance behind and corroding the fuel components.

When you find old fuel in your riding mower, drain the fuel tank and add fresh fuel. Add a fuel additive like Sea Foam Motor Treatment to your gas to clean and remove moisture from the fuel system.

Read more about making the right fuel choice and caring for your riding mower fuel here.

Clogged Fuel Lines Keep Your Riding Mower from Starting After Winter

Fuel lines can become clogged by old fuel. Locate a clogged line by stopping the fuel flow and removing an end of the line and placing it in a container.

Make sure the container is placed lower than the fuel tank because fuel cannot run uphill without the assistance of a fuel pump.

Start your fuel flow and check the flow coming out of the line into the container. If you have good flow, reinstall the fuel line. If you don’t get a good flow, shut the fuel flow off and remove that section of line from the riding mower.

Spray carburetor cleaner into the line. What you’re trying to do is loosen up the clog. Next, blow compressed air into the line to free the line of the clog. Repeat spraying with carb cleaner and blowing the line out with air until the blockage is removed.

Reinstall the line once it is free of the clog. Install a new section of the fuel line that is the same length and diameter when you are unable to unclog the line or the line is cracked and prone to leaking.

Dirty Carburetor Keeps Your Riding Mower from Starting After Winter

A little fuel is stored in the carburetor fuel bowl after it leaves the fuel tank. Old fuel can gum up and leave sticky and crusty deposits in the carburetor.

The fuel jet can become clogged and the small components can become stuck not allowing the proper amount of fuel to get to the engine to form a combustion.

If you’re getting sufficient fuel flow to the carburetor, but fuel isn’t getting to the engine, the mower won’t start. You will have to take your carburetor apart and clean it with carburetor cleaner to remove the buildup preventing it from functioning properly.

Follow the instructions in “How to Clean a Riding Lawn Mower Carburetor: Step-By-Step” to clean the carburetor. If you are unable to sufficiently clean it or find any damaged parts, you may have to rebuild it or replace it with a new carburetor.

Bad Spark Plug Keeps Your Riding Mower from Starting After Winter

When the riding mower is not used for some time, the spark plug can begin to corrode causing starting problems. Remove the spark plug with a socket wrench and inspect it for signs of corrosion.

Replace a spark plug that is corroded, very dark in color, or damaged.

If your spark plug is in good condition, but dirty or covered with carbon, clean it with a wire brush. Install your new or cleaned spark plug after you confirm it is gapped to the engine manufacturer’s specification. Then, securely attach the spark plug wires.

Bad or Dead Battery Keeps Your Riding Mower from Starting After Winter

A lawn mower battery left in the cold can freeze and no longer hold a charge. You don’t have to worry about your battery freezing if it is fully charged.

However, if it is not, there is a good chance you ruined your battery over the cold winter season. See the chart below for the temperatures when batteries freeze when they are not fully charged.

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
Winter Battery Freezing Temperatures

Check your battery to determine its charging level using an ohmmeter. Most riding lawn mowers use a 12-volt battery. A fully charged battery is one that reads 12.7 volts.

If it is less than this, charge the battery using the steps below. If you find your battery won’t hold a charge, replace it with a new lawn mower battery.

Charging a riding lawn mower battery

Charging a lawn mower battery requires a battery charger and cables. You should always wear protective gear before attempting to charge your lawn mower battery. Here are the steps for charging a lawn mower battery:

  • Put on your safety gear so that your eyes and skin are protected from acid or electrical shock.
  • Get access to the battery and its terminals. You may need the screwdriver to uncover the lawn mower’s body to get access to the battery or battery casing.
  • Leave the battery in its casing with the terminal cables attached.
  • Connect the charging cables starting with the positive cable first (The red one with the plus sign on it)
  • Connect the negative cable next (The black one with the negative sign on it). Remember: Positive cable (Red +) is the last one off and the first one on.
  • Make sure that your skin only touches the rubber coating of the charging cables and clamps.
  • Set the charger’s voltage level and amp level to the desired level. The average volt level for lawn mowers is usually 12 volts. More amperage charges the battery faster (Start with two amps and work up to no more than 10 amps).
  • If your charger has a battery charging gauge, keep the charger connected until the battery is fully charged. A 10 amp charger usually takes about one hour for full charging of your lawn mower battery.

Corroded Electrical Components Keep Your Riding Mower from Starting After Winter

Storing your lawn mower when it isn’t free of debris or moisture can cause corrosion to develop on your components. Check your safety switches and wiring to make sure they make good connections and are not corroded.

Common Winter Storage Questions & Answers

Should You Remove Your Lawn Mower Battery for Winter Storage?

A battery must either be removed from your lawn mower or fully charged when leaving it in your mower for winter storage.

A fully charged battery will not freeze. If you are not confident your battery is fully charged or you just want peace of mind it won’t freeze, remove the battery. Store it in a cool dry location away from any moist or humid areas.

Should You Empty the Lawn Mower Fuel Tank for Winter Storage?

You must empty the lawn mower fuel tank or add a fuel stabilizer to the gasoline if you choose to leave fuel in the tank for winter storage. Follow these instructions for the method you choose to use when preparing your lawn mower for storage during the winter season:

Empty the lawn mower fuel tank for winter storage

Use a fuel siphon pump and empty the fuel tank into a container designed to hold fuel. Start and allow your lawn mower to run until it stops because the engine is no longer getting fuel. This will allow most of the fuel to be removed from the fuel system.

Stabilize your gas when leaving fuel in the fuel tank for winter storage

Add a fuel stabilizer to the gasoline as instructed on the bottle. I like a product called Sea Foam Motor Treatment. You can find more information about it in this guide.

Once you have the fuel and stabilizer mixed in your fuel tank, start and allow the mower to run for a few minutes to allow the treated fuel to work its way through the system before storing.

Still Having Problems With Your Riding Mower?

As a lawn mower owner, when you own it long enough, you are going to run into different types of problems. This may include problems where your riding mower is smoking, cutting uneven, losing power, not starting, leaking fuel, and more.

Check out this handy guide including charts for common riding mower problems and solutions:
Common Riding Lawn Mower Problems & Solutions.

If you are unable to fix your riding mower or don’t want to attempt a more complicated repair, have your local lawn mower dealership or repair shop for assistance.