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Why Won’t My Riding Lawn Mower Start After Winter?

by Jack Grover
person riding red mower
Reading time: 21 min Prefer to listen?

Having trouble starting your riding lawn mower after the winter season? You’re not alone. Many people face issues with their lawn mower engines during this time, and the most common culprit is stale fuel.

Still, there are also other things that can prevent you from giving your yard a fresh spring cut.

Because of that, you shouldn’t dive straight into troubleshooting. Instead, thoroughly inspect your machine to find the underlying issues.

We will guide you through the essential checks to ensure you cover all bases.

Let’s take a closer look at the most common reasons your riding lawn mower won’t start after winter and practical solutions to fix these problems.

Key Takeaways

  • Common causes that prevent your mower from starting include old gas, clogged fuel lines, dirty carburetor, bad spark plug, dead battery, and corroded electrical components.
  • Proper battery maintenance is essential to prevent loss of charge and freezing during winter.
  • To fix the problem with old gas, drain it from the fuel tank and replace it with fresh fuel.
  • Unclog the fuel line by using a carburetor cleaner and applying compressed air.
  • Corroded electrical components can disrupt electricity flow; clean such areas using a wire brush or sandpaper.
  • Seeking expert assistance from a local lawn mower servicing provider can provide valuable help in troubleshooting and resolving starting problems.

Things To Check First

Before going any further, let’s check a few things first to make sure your riding lawn mower is ready to go after the winter break.

The most basic thing to inspect is the gas tank. Ensure it’s not empty because sometimes people forget to fill it up before storing their mower for winter. If the tank is empty, simply fill it with fresh fuel.

Another important thing to check is the oil. See if it’s not too thick, and ensure there’s enough oil in the tank. Thick oil can make it difficult for the engine to start, so if necessary, replace the old oil with fresh oil of the recommended viscosity.

Next, examine the spark plug. To do this, remove it by pulling off the rubber cover and using a socket wrench to loosen it. Take a look at the end of the spark plug that screws into the mower. If you notice it’s very dark, rusted, or corroded, replacement may be necessary.

If you’ve checked all of these things and your riding lawn mower still isn’t turning on, consider cleaning or replacing the carburetor.

However, before attempting this task yourself, we recommend taking your mower to a repair shop where experts can properly diagnose and fix any issues.

Common Causes

As you can see, if your riding lawn mower won’t start after winter, there are several common causes you should check.

Let’s go over these in more detail below, so you can fix the problem to get your mower up and running again.

Old Gas

Ah, old gas. It’s one of the most common culprits when your riding lawn mower refuses to start after a long winter slumber.

Fuel, over time, breaks down and becomes less effective, leaving behind a sticky residue that can clog up the fuel components in your mower. It can cause issues with fuel flow and prevent the engine from starting properly.

To fix this problem, the first step is to drain the old gas from the fuel tank. Do this in a well-ventilated area and follow proper safety precautions.

Once the old gas has been drained, fill the tank with fresh fuel.

To further clean and remove any moisture from the fuel system, it’s recommended to choose the fuel with a fuel additive. This substance will help break down any remaining residue and improve the overall performance of your mower’s engine.

Clogged Fuel Lines

When faced with a clogged fuel line, locate the blockage and take the necessary steps to remove it.

To do this, stop the fuel flow and remove one end of the line, placing it in a container positioned lower than the fuel tank. It will allow you to check the flow of fuel coming out of the line into the container.

If you have good flow, you can reinstall the fuel line. Yet, if there is no or poor flow, you’ll need to proceed with unclogging it.

One effective method for unclogging a fuel line is by using carburetor cleaner and compressed air.

  1. First, spray carburetor cleaner into the line to loosen up any clogs.
  1. Blow compressed air into the line to free it from any blockages.
  1. Repeat this process of spraying with carb cleaner and blowing out with air until the blockage is completely removed.
  1. Once cleared, reinstall the fuel line and ensure it’s securely attached.

If you cannot unclog the line or if it’s cracked and prone to leaking, replace that section with a new one of equal length and diameter.

Alternatively, you could ask a professional for help.

Here’s a list of the pros and cons of doing the task yourself to give you a better idea of what you’re getting into.

+ Effectively clears clogs in fuel lines.
+ Can be done without professional assistance.
+ Cost-effective solution compared to replacing the entire system.
– May require multiple attempts before achieving desired results.
– Potential risk of damaging or breaking fragile parts if too much pressure is applied during the blowing process.
– Requires tools such as wrenches or pliers for removing/reinstalling lines.

Dirty Carburetor

screwdriver in person's hand

Sometimes, to get your mower up and running, all you need to do is give that dirty carburetor a good cleaning.

Old fuel can leave sticky and crusty deposits in the carburetor, clogging the fuel jet and preventing the proper amount of fuel from reaching the engine for combustion. This buildup can cause your riding lawn mower to fail to start.

To clean the carburetor, you’ll need to take it apart and use carburetor cleaner to remove the stubborn deposits.

Follow this step-by-step guide for detailed instructions.

Step 1: Cleaning

  • Turn off the engine.
  • Clean the exterior of the lawn mower engine.
  • Tidy up your work area to avoid losing small parts and ensure proper lighting.

Step 2: Access the Carburetor

  • Remove the air filter housing to access the carburetor. 
  • Loosen the fasteners and store them safely for reinstallation. 
  • Inspect the air filter. Clean or replace it as necessary.

Step 3: Remove the Carburetor

  • Wear skin-protective gloves and use a carburetor cleaner to clean its part.
  • Remove the entire carburetor from the engine.
  • Disconnect the throttle and choke linkage cables.
  • Store fasteners safely for reinstallation. 
  • Before removing fuel lines, prepare a container to catch the fuel.

Step 4: Disassemble the Carburetor

  • Clean around the bowl with a carburetor cleaner. 
  • Unbolt the fuel bowl and remove the float.

 Step 5: Replace Worn–Out Parts

  • If necessary, replace damaged parts with new ones. 
  • Consider getting a repair kit for major parts replacements. 

Step 6: Clean the Carburetor and Its Parts

  • Spray carburetor cleaner inside the housing, and clean its parts. 
  • Soak parts in a bucket filled with a liquid carburetor cleaner for thorough cleaning.  

Step 7: Reassemble the Carburetor

Step 8: Test the Lawn Mower

  • Inspect the lawn mower to ensure all parts have been appropriately reattached.
  • Check for any loose screws or bolts and tighten them.
  • Make sure the fuel tank is closed securely and there is no leakage.
  • After reassembly, add fuel to the tank and start the mower.
  • If problems persist with starting the mower, consider taking it to a repair shop.

Following these steps will help in maintaining a smooth-running lawn mower. For more detailed steps or specific instructions related to your lawn mower model, refer to the user’s manual or consult a professional.

Bad Spark Plug

If you’re experiencing trouble getting your riding mower going, one possible culprit could be a bad spark plug.

Over time, when the mower isn’t used, the spark plug can begin to rust, which can lead to starting problems.

To check if your spark plug is the issue, remove it with a socket wrench and inspect it for signs of corrosion. If the spark plug is corroded, very dark in color, or damaged in any way, it’s best to replace it.

On the other hand, if your spark plug looks to be in good condition but is dirty or covered with carbon buildup, you may be able to salvage it by cleaning it with a wire brush. Clean all the debris off and ensure the electrode gap meets the engine manufacturer’s specifications before reinstalling it.

Once the spark plug is cleaned or replaced and securely attached to its wires, try starting your riding lawn mower again. A bad spark plug can often cause issues with starting after winter storage, so taking care of this component can help get your mower up and running smoothly once again.

Bad or Dead Battery

person fixing wire in engine

If you’ve already checked the spark plug and your riding lawn mower still won’t start after winter, another possible culprit could be a bad or dead battery.

When left in the cold, a lawn mower battery can freeze and lose its ability to hold a charge. This is especially true if the battery wasn’t fully charged before winter.

Here’s a helpful table that shows battery freezing temperatures for various models.

Battery charge12-volt batteries6-volt batteriesBattery Freezing Temperature
100%12.78 V6.39 V-80°F 
92%12.66 V6.33 V-71.3°F
85%12.57 V6.28 V-62°F
62%12.27 V6.13 V-16°F
40%11.97 V5.98 V+5°F
20%11.67 V5.84 V+19°F
Zero charge+20°F

You can use an ohmmeter to determine your battery’s charging level. Most riding lawn mowers use a 12-volt battery, and a fully charged battery should read around 12.7 volts. If your battery reads lower than this, it may need to be charged.

You can follow these steps to charge it:

  1. Connect the charger cables to the corresponding terminals on the battery, ensuring that the positive cable is connected to the positive terminal and the negative cable is connected to the negative terminal.
  1. Plug in the charger and turn it on.
  1. Let the charger run until it indicates the battery is fully charged.
  1. Disconnect the charger cables from the battery terminals.

If your battery doesn’t hold a charge even after charging it, it may be time to replace it with a new one. In such a case, be sure to choose a compatible replacement based on your mower’s specifications.

Corroded Electrical Components

Finally, you should check for signs of corrosion on the electrical components, such as safety switches and wiring. Storing your lawn mower when it isn’t free of debris or moisture can cause corrosion to develop on these components.

Corrosion can disrupt the flow of electricity and prevent your riding lawn mower from starting.

To check for corrosion, visually inspect the safety switches and wiring for any buildup or discoloration. If you notice any signs of corrosion, gently clean the affected areas using a wire brush or sandpaper. Be sure to disconnect the battery before cleaning to avoid any accidental electrical shocks.

To make it easier to understand, here is a table that shows common signs of corrosion and their possible effects on your lawn mower’s electrical system:

Sign of CorrosionPossible Effect
Buildup or rustPoor connection
Discoloration Intermittent power supply
Loose wiresNo power

The Bottom Line

Having trouble starting your riding lawn mower after the winter season can be frustrating, but it’s not impossible to solve.

You need to check a few essential things to take care of this issue.

First and foremost, make sure to drain the old fuel from the tank and replace it with fresh fuel.

If draining and replacing the fuel doesn’t solve the problem, other possible faults may prevent your mower from starting. It could be a spark plug issue or a clogged carburetor.

If you follow our expert advice and helpful solutions, you’ll be able to tackle the problem head-on and prevent future issues that may hinder your mower’s performance.

Happy mowing!

Frequently Asked Questions

Can I use the same fuel from last season in my riding lawn mower?

No, using the same fuel from last season in your riding lawn mower is not recommended. Stale fuel is a common reason for starting issues, so it’s best to drain the old fuel and fill the tank with fresh fuel.

Are there any specific additives that can help prevent fuel from going stale?

Yes, there are specific additives available that can help prevent fuel from going stale. They slow down the process of fuel degradation and keep it fresh for longer periods.

These include but are not limited to:

  • acetone,
  • butyl rubber,
  • ether,
  • ferrous picrate,
  • nitrous oxide (nitrous),
  • nitromethane (nitro),
  • oxyhydrogen.

How often should I drain the fuel from my riding lawn mower?

To prevent fuel from going stale, it’s recommended to drain the fuel at least once a year. It helps avoid issues caused by stale fuel after winter storage.

What should I do if I have already replaced the fuel and the mower still won’t start?

If you have already replaced the fuel and your riding lawn mower still won’t start, there may be other possible faults. Contact a local lawn mower servicing provider for further investigation and assistance.

Can I contact the local garden machinery supplier for assistance even if I didn’t purchase my riding lawn mower from them?

Yes, you can contact the local garden machinery supplier for assistance even if you didn’t purchase your riding lawn mower from them. They should be willing to provide further investigation and support in fixing the issue. However, bear in mind that it may come with additional costs.

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