Getting your lawn mower to start after a period of inactivity can be frustrating. It’s a common issue, especially after the winter months or during periods of infrequent use. This comprehensive guide will walk you through the common culprits and provide step-by-step instructions to diagnose and resolve the problem, ensuring your lawn mower is ready to tackle your lawn.
Understanding Why Your Lawn Mower Won’t Start
Several factors can contribute to a lawn mower’s refusal to start after sitting idle. Identifying the root cause is the first step towards a successful fix. Common culprits include fuel issues, spark plug problems, air filter blockages, and battery troubles (for electric start models).
Fuel System Issues
The fuel system is often the primary suspect when a lawn mower refuses to start after storage. Gasoline degrades over time, leading to varnish and gum deposits that can clog the carburetor and fuel lines.
Stale Fuel: Gasoline begins to break down and oxidize after about 30 days. This process leads to the formation of sticky residues that can clog the small passageways within the carburetor.
Clogged Carburetor: The carburetor mixes air and fuel to create the combustible mixture needed to start the engine. When it’s clogged, the engine can’t get the fuel it needs.
Fuel Line Blockages: Fuel lines can also become clogged with old fuel deposits, restricting the flow of gasoline to the carburetor.
Spark Plug Problems
The spark plug ignites the air-fuel mixture in the engine’s cylinder. A faulty or fouled spark plug can prevent the engine from starting.
Dirty or Fouled Spark Plug: Carbon deposits, oil, or fuel can accumulate on the spark plug electrode, preventing it from generating a strong spark.
Damaged Spark Plug: The spark plug electrode can become worn, cracked, or corroded over time, reducing its effectiveness.
Incorrect Spark Plug Gap: The gap between the spark plug electrodes must be within the manufacturer’s specifications for proper ignition.
Air Filter Obstructions
The air filter prevents dirt and debris from entering the engine. A dirty or clogged air filter restricts airflow, leading to a lean fuel mixture and starting problems.
Dirty Air Filter: Over time, the air filter becomes clogged with dust, grass clippings, and other debris, reducing the amount of air that reaches the engine.
Restricted Airflow: A clogged air filter can cause the engine to run poorly, misfire, or fail to start altogether.
Battery Problems (Electric Start Models)
Electric start lawn mowers rely on a battery to power the starter motor. A dead or weak battery can prevent the engine from cranking.
Dead Battery: The battery may have discharged over time, especially if the lawn mower has been stored for an extended period.
Corroded Terminals: Corrosion on the battery terminals can prevent a good electrical connection, hindering the flow of current to the starter motor.
Faulty Starter Motor: Although less common, a faulty starter motor can also prevent the engine from cranking.
Step-by-Step Troubleshooting and Solutions
Now that we’ve covered the common causes, let’s dive into troubleshooting and solutions. Follow these steps to diagnose and fix your lawn mower.
Step 1: Prepare Your Workspace and Safety Precautions
Before you begin any repairs, ensure you have a well-ventilated workspace and take necessary safety precautions. Disconnect the spark plug wire to prevent accidental starting. Wear gloves to protect your hands, and eye protection to shield your eyes from debris. Keep a fire extinguisher nearby.
Step 2: Check the Fuel
The first thing to inspect is the fuel. Old or contaminated fuel is a common culprit.
- Smell the Fuel: Remove the fuel cap and smell the fuel. If it smells stale or varnished, it’s likely degraded.
- Drain the Fuel Tank: Carefully drain the old fuel into an approved container. Dispose of it properly at a local recycling center or hazardous waste facility.
- Refill with Fresh Fuel: Fill the tank with fresh, high-quality gasoline. Consider adding a fuel stabilizer to prevent future degradation.
Step 3: Clean or Replace the Spark Plug
A faulty spark plug can prevent the engine from starting.
- Locate the Spark Plug: The spark plug is typically located on the side of the engine.
- Disconnect the Spark Plug Wire: Carefully pull the spark plug wire from the spark plug.
- Remove the Spark Plug: Use a spark plug wrench to remove the spark plug.
- Inspect the Spark Plug: Examine the spark plug for signs of damage, carbon buildup, or fouling.
- Clean the Spark Plug (if applicable): If the spark plug is only slightly dirty, you can clean it with a wire brush and spark plug cleaner.
- Check the Spark Plug Gap: Use a spark plug gap tool to ensure the gap between the electrodes is within the manufacturer’s specifications. Adjust the gap if necessary.
- Replace the Spark Plug (if necessary): If the spark plug is heavily fouled, damaged, or corroded, replace it with a new one that matches the manufacturer’s specifications.
- Reinstall the Spark Plug: Carefully reinstall the spark plug and tighten it to the proper torque.
- Reconnect the Spark Plug Wire: Reconnect the spark plug wire to the spark plug.
Step 4: Inspect and Clean the Air Filter
A clogged air filter can restrict airflow and prevent the engine from starting.
- Locate the Air Filter: The air filter is typically housed in a plastic case on top of the engine.
- Remove the Air Filter Cover: Remove the air filter cover to access the air filter.
- Inspect the Air Filter: Examine the air filter for dirt, debris, and damage.
- Clean the Air Filter (if applicable): If the air filter is a foam type, wash it with soap and water, squeeze out the excess water, and allow it to dry completely. If it’s a paper type, gently tap it to remove loose debris.
- Replace the Air Filter (if necessary): If the air filter is heavily soiled or damaged, replace it with a new one that matches the manufacturer’s specifications.
- Reinstall the Air Filter Cover: Reinstall the air filter cover.
Step 5: Address Carburetor Issues
A clogged carburetor is a common cause of starting problems.
- Try Carburetor Cleaner: Spray carburetor cleaner into the carburetor’s air intake while attempting to start the engine. This may help dissolve minor deposits.
- Clean the Carburetor (More involved): If carburetor cleaner doesn’t work, you may need to remove and clean the carburetor. This requires some mechanical skill and knowledge. Consult your lawn mower’s service manual or watch online tutorials for guidance. Carburetor cleaning involves disassembling the carburetor, cleaning the individual parts with carburetor cleaner, and reassembling it. Be sure to take pictures as you disassemble the carburetor to aid in reassembly.
- Replace the Carburetor (if necessary): If the carburetor is severely clogged or damaged, replacing it may be the easiest option.
Step 6: Check the Battery (Electric Start Models)
If your lawn mower has an electric start, check the battery.
- Check Battery Voltage: Use a multimeter to check the battery voltage. A fully charged 12-volt battery should read around 12.6 volts.
- Charge the Battery: If the battery voltage is low, charge it with a battery charger.
- Clean Battery Terminals: Clean any corrosion from the battery terminals with a wire brush and a solution of baking soda and water.
- Test the Battery: If the battery holds a charge but the lawn mower still won’t start, have the battery tested at an auto parts store.
- Replace the Battery (if necessary): If the battery is faulty, replace it with a new one that matches the manufacturer’s specifications.
Step 7: Inspect the Fuel Lines
Clogged or cracked fuel lines can restrict fuel flow.
- Visually Inspect the Fuel Lines: Examine the fuel lines for cracks, leaks, or kinks.
- Check for Blockages: Disconnect the fuel lines and check for blockages. You can use compressed air to blow out any debris.
- Replace Fuel Lines (if necessary): Replace any damaged or blocked fuel lines with new ones.
Preventative Maintenance for Future Starts
Preventing starting problems is always better than fixing them. Implement these maintenance practices to ensure your lawn mower starts reliably every time.
- Use Fuel Stabilizer: Add fuel stabilizer to your gasoline, especially before storing the lawn mower for extended periods. Fuel stabilizer prevents the fuel from degrading and forming deposits.
- Drain the Fuel Tank: Before storing the lawn mower for the winter, drain the fuel tank completely. This prevents old fuel from clogging the carburetor.
- Clean the Lawn Mower Regularly: Regularly clean the lawn mower to remove grass clippings and debris. Pay particular attention to the air filter and engine cooling fins.
- Change the Oil Regularly: Change the engine oil according to the manufacturer’s recommendations. Fresh oil lubricates the engine and helps prevent wear and tear.
- Sharpen the Blades: Sharpen the lawn mower blades regularly to ensure a clean cut. Dull blades can strain the engine.
- Store Properly: Store the lawn mower in a dry, sheltered location to protect it from the elements.
Additional Tips and Considerations
- Check the Owner’s Manual: Always consult your lawn mower’s owner’s manual for specific maintenance recommendations and troubleshooting tips.
- Pull the Starter Cord Slowly: When attempting to start the lawn mower, pull the starter cord slowly and steadily. Avoid yanking the cord, as this can damage the starter mechanism.
- Prime the Engine: Some lawn mowers have a primer bulb that you need to press several times before starting. This primes the engine with fuel.
- Check the Safety Features: Ensure that all safety features, such as the blade brake control, are functioning properly.
By following these steps and implementing preventative maintenance practices, you can ensure that your lawn mower starts reliably every time, saving you time and frustration. Remember to always prioritize safety when working with gasoline and mechanical equipment.
Why won’t my lawn mower start after sitting for the winter?
The most common reason a lawn mower refuses to start after sitting for an extended period, such as over the winter, is stale fuel. Gasoline degrades over time, leading to a gummy residue that can clog the carburetor and fuel lines. This residue prevents the proper fuel-air mixture needed for combustion, effectively starving the engine.
Another frequent culprit is a dead or weak battery, especially in electric start mowers. Cold temperatures and lack of use can significantly reduce a battery’s charge, rendering it unable to crank the engine. Corroded battery terminals can also hinder the flow of electricity, preventing the mower from starting even if the battery has some charge.
How do I properly prepare my lawn mower for long-term storage?
Before storing your lawn mower for the off-season, thoroughly clean it to remove any grass clippings or debris. These materials can attract moisture and contribute to corrosion. Empty the fuel tank completely or add a fuel stabilizer to prevent the gasoline from degrading and forming gummy deposits.
Disconnect the spark plug wire to prevent accidental starts and change the engine oil to remove contaminants that can damage internal components during storage. Consider storing the mower in a dry, sheltered location to protect it from the elements and further extend its lifespan.
What is fuel stabilizer and how does it work?
Fuel stabilizer is a chemical additive designed to prevent gasoline from degrading and forming varnish or gum deposits during storage. It works by inhibiting the oxidation process that causes fuel to break down, effectively prolonging the fuel’s usability and preventing it from clogging the carburetor and fuel lines.
Using fuel stabilizer is a simple process. Just add the recommended amount, as specified on the product label, to the fuel tank before storing your lawn mower. Run the engine for a few minutes to ensure the treated fuel circulates through the entire fuel system, providing comprehensive protection.
How do I clean a clogged carburetor on my lawn mower?
Cleaning a clogged carburetor usually involves removing it from the engine. Disconnect the fuel lines and any linkages, taking note of their positions for reassembly. Then, carefully disassemble the carburetor, noting the location of each component.
Use carburetor cleaner spray to thoroughly clean all parts, including the jets, bowls, and passages. Pay special attention to any visible deposits or obstructions. After cleaning, reassemble the carburetor, ensuring all parts are properly aligned and secured, and then reinstall it on the engine.
How can I tell if my lawn mower battery is dead or just needs charging?
A completely dead battery will show no voltage reading when tested with a multimeter. If you connect a charger and the battery doesn’t accept any charge, it is likely dead. Often, even a boost from a jump starter won’t revive a completely dead battery.
A battery that simply needs charging will typically show a low voltage reading on the multimeter, such as below 12 volts. When connected to a charger, it will begin to accept a charge, and the voltage will gradually increase. After charging, it should be able to hold a charge and start the lawn mower.
What should I do if my lawn mower pulls over but won’t start?
If your lawn mower pulls over but fails to start, begin by checking the spark plug. Remove it and inspect for fouling, such as carbon buildup or oil deposits. Clean or replace the spark plug as needed and ensure the spark plug gap is set correctly according to the manufacturer’s specifications.
Next, confirm that the fuel shut-off valve is open and that there is fresh fuel in the tank. If the fuel is old, drain it and replace it with fresh gasoline. Additionally, inspect the air filter to ensure it’s clean and not obstructed, as a dirty air filter can restrict airflow and prevent the engine from starting.
How often should I change the oil in my lawn mower?
It is generally recommended to change the oil in your lawn mower at least once a year, or every 25 to 50 hours of use, whichever comes first. Regular oil changes help to remove contaminants and maintain proper lubrication, extending the life of your engine.
For heavy use or harsh conditions, such as dusty environments, more frequent oil changes may be necessary. Always refer to your lawn mower’s owner’s manual for specific recommendations on oil change intervals and the correct type of oil to use.