Cold weather can wreak havoc on many things, and your lawnmower is no exception. That reliable machine that roared to life all summer long can suddenly become stubborn and refuse to start when the temperature drops. Understanding the common culprits behind this cold-weather starting problem is the first step toward getting your lawnmower back in action. This article will delve into the reasons why your lawnmower might be struggling in the cold and provide solutions to get it running smoothly again.
The Impact of Cold on Lawnmower Engines
Cold temperatures affect various components of your lawnmower’s engine, making it harder to start. The primary factors influenced are fuel vaporization, battery performance (for electric start models), and oil viscosity. Let’s examine each of these more closely.
Fuel Vaporization Challenges
Gasoline needs to vaporize – turn into a gas – to mix with air and create a combustible mixture that ignites in the engine cylinder. Cold weather significantly reduces the rate of vaporization. When the gasoline is cold, it’s less likely to evaporate effectively, leading to a lean fuel mixture. This lean mixture, having insufficient fuel vapor relative to air, can prevent the engine from starting, especially during colder months. This problem is amplified in older carburetors, which may not be optimally tuned for cold weather.
Battery Performance in the Cold (Electric Start Models)
If your lawnmower has an electric start, the battery plays a vital role. Cold temperatures dramatically reduce a battery’s ability to deliver power. The chemical reactions within the battery slow down, hindering its capacity to provide the necessary cranking amperage to turn over the engine. A battery that functions perfectly well in warmer weather might struggle considerably when cold. This is because the internal resistance of the battery increases in cold conditions, limiting its ability to discharge electricity effectively.
Oil Viscosity Issues
Engine oil thickens in cold temperatures, increasing its viscosity. This thicker oil creates more resistance within the engine as it tries to move through the various components. The engine has to work harder to turn over, which puts additional strain on the starting system. If the oil is too thick, it can also impede the flow of oil to critical engine parts, potentially causing damage if the engine eventually starts. Choosing the correct oil weight for your climate is important, with lighter-weight oils often recommended for colder environments.
Common Culprits Preventing Cold Starts
Now that we understand how cold impacts the engine, let’s identify the specific components and problems that often prevent a lawnmower from starting in cold weather.
The Carburetor and Fuel System
The carburetor is responsible for mixing fuel and air in the correct proportions. Several carburetor-related issues can arise in cold weather, preventing the lawnmower from starting.
Clogged Carburetor Jets
Tiny passages within the carburetor, called jets, can become clogged with varnish or deposits from old fuel. This is particularly common when lawnmowers are stored for the winter without proper fuel stabilization. These clogs restrict fuel flow, leading to a lean mixture that makes starting difficult.
Stale Fuel
Gasoline degrades over time, especially when exposed to air. Stale fuel loses its volatile components, reducing its ability to vaporize and ignite. Using old fuel in cold weather makes starting even more challenging. Ideally, you should use fresh fuel that is less than 30 days old, or use a fuel stabilizer.
Choke Problems
The choke enriches the fuel mixture by restricting airflow, which is crucial for cold starting. If the choke is not functioning correctly – either not closing completely or not opening after the engine starts – it can prevent the engine from starting or cause it to stall soon after.
Spark Plug Problems
The spark plug ignites the fuel-air mixture in the engine cylinder. A faulty spark plug can prevent the engine from starting, regardless of the temperature.
Fouled Spark Plug
A spark plug can become fouled with carbon deposits, oil, or fuel residue. These deposits can create an insulating layer that prevents the spark from jumping across the electrode gap. A fouled spark plug is unable to effectively ignite the fuel-air mixture.
Weak Spark
Even if the spark plug isn’t visibly fouled, it may be producing a weak spark due to a faulty ignition coil or other electrical issues. A weak spark may not be strong enough to ignite the fuel-air mixture, especially in cold conditions where vaporization is reduced.
Battery Issues (Electric Start Models)
As mentioned earlier, the battery is crucial for electric start lawnmowers. Cold weather exacerbates any existing battery problems.
Low Battery Charge
A battery with a low charge will struggle to provide enough power to crank the engine, particularly in the cold. The engine will turn over slowly, or not at all. A battery maintainer is your friend here.
Corroded Terminals
Corrosion on the battery terminals can impede the flow of electricity, reducing the battery’s ability to deliver power to the starter motor. Clean battery terminals will improve the electrical connection.
Other Potential Issues
Beyond the carburetor, spark plug, and battery, other factors can contribute to cold-weather starting problems.
Dirty Air Filter
A dirty air filter restricts airflow to the engine, which can affect the fuel-air mixture and make starting more difficult. This is a common issue to overlook.
Loose or Damaged Wiring
Loose or damaged wiring can disrupt the electrical system, preventing the engine from starting. Always check the wiring for proper connections.
Troubleshooting Steps: Getting Your Lawnmower Started in the Cold
Now that we’ve identified the potential causes, let’s move on to practical troubleshooting steps to get your lawnmower running when it’s cold.
Checking the Fuel System
The fuel system is a good place to start your troubleshooting.
Ensure Fresh Fuel
The first step is to ensure you’re using fresh fuel. Drain any old fuel from the tank and replace it with fresh gasoline. Consider adding a fuel stabilizer to the fuel to prevent it from degrading.
Inspect and Clean the Carburetor
If you suspect the carburetor is clogged, carefully remove it and inspect it for any signs of debris or varnish. Clean the carburetor jets and passages with carburetor cleaner. If you’re not comfortable disassembling the carburetor, you can try using a carburetor cleaner spray directly into the carburetor intake while attempting to start the engine.
Check the Choke
Make sure the choke is functioning correctly. When you engage the choke, it should close completely. If it’s not closing fully, adjust the choke linkage or cable. After the engine starts, the choke should open fully to allow normal airflow.
Inspecting the Spark Plug
The spark plug is an easy check that could save time.
Remove and Inspect the Spark Plug
Remove the spark plug and inspect it for fouling, cracks, or damage. Clean the spark plug with a wire brush or spark plug cleaner. Check the spark plug gap with a feeler gauge and adjust it to the manufacturer’s specifications.
Test for Spark
To test for spark, connect the spark plug to the spark plug wire and ground the spark plug body against the engine block. Pull the starter rope or turn the ignition key (electric start). You should see a strong, blue spark jumping across the electrode gap. If there’s no spark, or the spark is weak and yellow, replace the spark plug or investigate the ignition coil.
Addressing Battery Issues (Electric Start Models)
If you have an electric start model, pay special attention to the battery.
Check the Battery Charge
Use a voltmeter to check the battery’s voltage. A fully charged 12-volt battery should read around 12.6 volts. If the voltage is significantly lower, charge the battery 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. Apply a thin coat of petroleum jelly to the terminals to prevent future corrosion.
Other Troubleshooting Tips
Don’t overlook these other potential problem areas.
Check the Air Filter
Remove the air filter and inspect it for dirt and debris. If the air filter is dirty, clean it with compressed air or replace it with a new one.
Inspect Wiring Connections
Check all wiring connections for looseness, corrosion, or damage. Ensure all connections are clean and tight.
Warm the Engine
Sometimes, simply warming the engine can help it start. You can try using a hair dryer to gently warm the engine block or carburetor. Be careful not to overheat any components. You can also park the lawnmower in a garage or shed that is warmer than outside.
Preventive Measures for Cold Weather Starting Problems
Preventing cold-weather starting problems is always better than dealing with them. Here are some steps you can take to prepare your lawnmower for cold weather.
Fuel Stabilization
Add a fuel stabilizer to the gasoline before storing the lawnmower for the winter. This will prevent the fuel from degrading and keep the carburetor clean. Run the engine for a few minutes after adding the stabilizer to ensure it circulates throughout the fuel system.
Proper Storage
Store the lawnmower in a dry, sheltered location, such as a garage or shed. This will protect it from the elements and help prevent corrosion.
Battery Maintenance (Electric Start Models)
If you have an electric start lawnmower, remove the battery and store it in a cool, dry place during the winter. Use a battery maintainer or trickle charger to keep the battery charged throughout the off-season.
Oil Change
Change the engine oil before storing the lawnmower for the winter. This will remove any contaminants that could damage the engine over time. Consider using a lighter-weight oil if you live in an area with very cold winters. Check the operator’s manual for the recommended oil type.
Regular Maintenance
Perform regular maintenance on your lawnmower, including cleaning the air filter, inspecting the spark plug, and lubricating moving parts. This will keep your lawnmower in good working condition and prevent problems from developing.
By understanding the reasons why your lawnmower might not start in cold weather and following the troubleshooting steps outlined in this article, you can increase the chances of getting it running smoothly. Regular maintenance and proper storage are essential for preventing cold-weather starting problems. With a little preparation, you can ensure that your lawnmower is ready to tackle the next mowing season, regardless of the temperature.
Why is it harder to start my lawnmower when it’s cold outside?
Cold weather significantly impacts the starting process of your lawnmower primarily due to the behavior of gasoline. At lower temperatures, gasoline evaporates less readily, making it more difficult to create the combustible air-fuel mixture needed for the engine to ignite. This is especially true for older lawnmowers or those with carburetors that are not precisely calibrated for optimal cold-weather performance.
Furthermore, engine oil thickens in the cold, increasing resistance within the engine. This added resistance makes it harder for the starter motor to turn the engine over, requiring more power from the battery. A weak or aging battery is further stressed by these conditions, making starting even more challenging.
What role does stale fuel play in cold weather starting problems?
Stale fuel is a common culprit when a lawnmower refuses to start, and its effects are exacerbated in cold weather. Gasoline degrades over time, especially when exposed to air, leading to a loss of volatile components essential for easy ignition. This degradation leaves behind gum and varnish deposits that can clog fuel lines, jets in the carburetor, and other critical fuel system components, further hindering the already difficult task of vaporization in cold temperatures.
Even if the engine eventually starts with stale fuel, it’s likely to run poorly, experiencing misfires, rough idling, and reduced power. Moreover, these deposits can cause long-term damage to the fuel system, requiring more extensive and costly repairs in the future. Using fresh fuel and a fuel stabilizer can prevent these issues.
How can I check if the spark plug is the problem?
To determine if the spark plug is the cause of your starting issues, first, carefully remove the spark plug from the engine. Visually inspect the spark plug for signs of damage, such as cracks in the porcelain insulator or excessive wear on the electrodes. Also, check for carbon fouling, which appears as a black, sooty deposit on the spark plug. A heavily fouled or damaged spark plug will not produce a reliable spark.
Next, reattach the spark plug wire to the spark plug and, while holding the spark plug against a grounded metal part of the engine, pull the starter cord. You should see a strong, consistent blue or white spark jumping across the gap between the electrodes. If the spark is weak, intermittent, or non-existent, the spark plug is likely faulty and needs to be replaced.
What kind of fuel stabilizer should I use, and when should I add it?
When selecting a fuel stabilizer, choose one specifically designed for small engines and gasoline used in power equipment. Look for a product that protects against oxidation, corrosion, and fuel degradation. Some stabilizers also contain detergents that help clean fuel system components. Reputable brands offer effective formulations that are compatible with most gasoline types.
Add fuel stabilizer to your lawnmower’s fuel tank when storing it for extended periods, typically during the off-season. It’s also beneficial to add it whenever you purchase fresh gasoline, especially if you anticipate the fuel sitting in the tank for more than a few weeks. Follow the dosage instructions on the fuel stabilizer container for the best results.
What should I do if the carburetor is clogged?
If you suspect a clogged carburetor, start by attempting to clean it externally. Use carburetor cleaner spray to thoroughly clean the visible parts of the carburetor, paying close attention to any accessible jets or openings. Sometimes, this alone can dislodge minor debris and improve fuel flow.
If external cleaning doesn’t solve the problem, you may need to disassemble the carburetor for a more thorough cleaning. This involves removing the carburetor from the engine, carefully disassembling it, and cleaning each component individually with carburetor cleaner and small brushes. Reassemble the carburetor with new gaskets and seals if possible, and reinstall it on the engine. Consider consulting a repair manual or professional for guidance if you’re not comfortable with this process.
How does the air filter affect starting in cold weather?
A dirty or clogged air filter restricts airflow to the engine, impacting the air-fuel mixture and making it difficult for the engine to start, particularly in cold weather when gasoline vaporization is already a challenge. Reduced airflow can lead to a richer mixture, flooding the engine and preventing proper combustion.
Check your air filter regularly, especially before the cold season, and clean or replace it as needed. A clean air filter ensures that the engine receives the proper amount of air for efficient combustion, improving starting performance and overall engine health. Consult your lawnmower’s manual for recommended air filter maintenance schedules.
Could a weak battery be the reason my lawnmower won’t start in the cold?
Yes, a weak battery is a common cause of starting problems in cold weather, especially for lawnmowers with electric start. Cold temperatures reduce the battery’s ability to deliver the necessary current to turn the engine over. A battery that’s nearing the end of its lifespan or hasn’t been properly maintained will struggle to provide sufficient power, especially when faced with the increased resistance of cold engine oil.
Have your battery tested with a load tester to determine its health. If the battery is weak or failing, replace it with a new one that meets the specifications for your lawnmower model. Consider using a battery maintainer or trickle charger during the off-season to keep the battery fully charged and extend its lifespan.