The frustration is palpable. You’re ready to tackle that overgrown lawn, you pull out the lawnmower, give the cord a yank… and nothing. Just the faint smell of gasoline and the dull ache in your shoulder. Lawnmowers, especially after a period of inactivity, can be notoriously stubborn. But don’t despair! The good news is that the reasons for this common problem are usually straightforward and often easily fixable. This comprehensive guide will walk you through the most likely culprits and provide you with the knowledge to get your mower roaring back to life.
The Prime Suspect: Stale Fuel
Let’s face it, gasoline isn’t designed to sit around. Over time, especially during the off-season when your lawnmower is hibernating, gasoline can degrade and become stale. This is the most frequent cause of starting problems in lawnmowers that have been idle for a while.
The Science of Stale Gas
Gasoline is a complex mixture of hydrocarbons. Over time, these hydrocarbons can break down, leading to the formation of gums and varnishes. These sticky substances can clog vital components in your lawnmower’s fuel system, preventing fuel from reaching the engine. Ethanol, often added to gasoline, exacerbates this problem. Ethanol attracts moisture, which can lead to phase separation, where the ethanol and water separate from the gasoline, creating a corrosive mixture that damages fuel lines and other components.
How to Identify Stale Gas
The most obvious sign is the smell. Fresh gasoline has a distinct, sharp odor. Stale gas, on the other hand, will often have a sour or varnish-like scent. Visually, stale gas might appear darker or cloudier than fresh gasoline.
The Solution: Draining and Replacing the Fuel
The best course of action is to drain the old fuel completely and replace it with fresh gasoline. Use a fuel stabilizer in the new gasoline to prevent future degradation, especially if you anticipate the lawnmower sitting unused for extended periods. Fuel stabilizer is crucial for long-term storage.
Draining the fuel is usually a simple process. Most lawnmowers have a drain plug located on the carburetor or at the bottom of the fuel tank. Consult your owner’s manual for the specific location and procedure for your model. Remember to dispose of the old gasoline properly, following local regulations.
Carburetor Clogs: A Common Obstacle
The carburetor is the heart of your lawnmower’s fuel system. It’s responsible for mixing air and fuel in the correct proportions to create a combustible mixture. When stale fuel degrades, it can leave behind gummy deposits that clog the carburetor’s tiny passages.
Understanding Carburetor Functionality
The carburetor contains jets and small orifices that precisely meter the fuel flow. Even a small amount of debris can block these passages, preventing the engine from receiving the fuel it needs to start.
Symptoms of a Clogged Carburetor
A clogged carburetor can manifest in several ways. The engine might not start at all, or it might start but run roughly and stall quickly. You might also notice a decrease in engine power or increased fuel consumption.
Cleaning a Carburetor: A Step-by-Step Approach
Cleaning a carburetor can seem daunting, but it’s often a manageable task for the average homeowner. You’ll need a few basic tools, including a screwdriver, pliers, carburetor cleaner, and possibly a set of carburetor cleaning brushes or wires.
First, disconnect the spark plug wire to prevent accidental starting. Then, carefully remove the carburetor from the engine, noting the location of all hoses and linkages. Disassemble the carburetor, paying close attention to the order of the parts. Soak the carburetor components in carburetor cleaner, and use the brushes or wires to clean out any stubborn deposits. Reassemble the carburetor, ensuring that all parts are properly seated, and reinstall it on the engine.
Always consult your lawnmower’s service manual for specific instructions and diagrams. Incorrect reassembly can lead to further problems.
The Spark Plug: Igniting the Flame
The spark plug is responsible for igniting the air-fuel mixture in the engine’s cylinder. A faulty or fouled spark plug can prevent the engine from starting.
Spark Plug Inspection: A Visual Check
Remove the spark plug and inspect it carefully. Look for signs of fouling, such as carbon deposits, oil, or gasoline. The electrode should be clean and free of corrosion.
Testing the Spark Plug: Is There Spark?
You can test the spark plug by grounding it against the engine block and pulling the starter cord. You should see a bright blue spark jump across the electrode gap. If there’s no spark or the spark is weak and yellow, the spark plug is likely faulty and needs to be replaced.
Spark Plug Replacement: A Simple Solution
Replacing a spark plug is a straightforward process. Simply remove the old spark plug with a spark plug wrench and install a new one, tightening it to the manufacturer’s specified torque. Always use the correct spark plug for your lawnmower model. Refer to your owner’s manual for the correct part number.
Air Filter Woes: Suffocating the Engine
The air filter prevents dirt and debris from entering the engine. A clogged air filter restricts airflow, which can prevent the engine from starting or cause it to run poorly.
Air Filter Examination: Is it Clean?
Remove the air filter and inspect it. If it’s dirty or clogged, clean or replace it. Foam air filters can often be washed with soap and water, while paper air filters should be replaced.
Air Filter Maintenance: Regular Cleaning or Replacement
Regularly cleaning or replacing the air filter is essential for maintaining your lawnmower’s performance and extending its lifespan. Check the air filter regularly, especially during dusty conditions.
The Battery (for Electric Start Models): Powering Up
If you have an electric start lawnmower, a weak or dead battery can prevent it from starting.
Battery Testing: Checking the Charge
Use a multimeter to test the battery’s voltage. A fully charged 12-volt battery should read around 12.6 volts. If the voltage is significantly lower, the battery needs to be charged or replaced.
Battery Charging: Replenishing the Power
Use a battery charger specifically designed for lawnmower batteries to recharge the battery. Follow the charger’s instructions carefully.
Battery Replacement: When It’s Time to Swap
If the battery won’t hold a charge, it’s time to replace it. Ensure you purchase a battery with the correct voltage and amperage for your lawnmower model.
Other Potential Culprits
While stale fuel, carburetor clogs, and spark plug issues are the most common reasons for a lawnmower not starting after sitting, other factors can also contribute to the problem.
Fuel Lines and Filters: Ensuring Fuel Delivery
Inspect the fuel lines for cracks or leaks. Replace any damaged fuel lines. Check the fuel filter for clogs and replace it if necessary.
Safety Interlock Switches: Preventing Accidental Starts
Lawnmowers are equipped with safety interlock switches that prevent the engine from starting unless certain conditions are met, such as the blade control lever being engaged or the operator being present. Check these switches to ensure they are functioning properly.
Low Oil Level: Protecting the Engine
Most lawnmowers have a low-oil sensor that prevents the engine from starting if the oil level is too low. Check the oil level and add oil if necessary.
Choke Mechanism: Assisting Cold Starts
The choke mechanism enriches the air-fuel mixture for cold starts. Ensure the choke is functioning properly and is engaged when starting a cold engine.
Preventative Measures: Avoiding Future Headaches
The best way to avoid lawnmower starting problems after a period of inactivity is to take preventative measures before storing the lawnmower.
Fuel Stabilizer: The Key to Long-Term Storage
Add fuel stabilizer to the gasoline before storing the lawnmower. This will prevent the fuel from degrading and forming gummy deposits.
Draining the Fuel: An Alternative Approach
Alternatively, you can drain the fuel tank completely before storing the lawnmower. This will prevent any fuel from degrading and causing problems.
Proper Storage: Protecting Your Investment
Store the lawnmower in a dry, sheltered location. This will protect it from the elements and prevent rust and corrosion.
By following these tips, you can significantly reduce the likelihood of encountering starting problems with your lawnmower after it has been sitting for a long time. Regular maintenance and proper storage are key to keeping your lawnmower running smoothly for years to come.
Why won’t my lawnmower start after it’s been stored for a long time?
A common reason lawnmowers refuse to start after a period of inactivity is due to stale fuel. Gasoline degrades over time, especially when exposed to air, leading to the formation of gums and varnishes that can clog the carburetor and fuel lines. These deposits restrict or prevent the proper flow of fuel to the engine, making it difficult or impossible for the lawnmower to ignite and run.
Another likely culprit is a dead or weakened battery, particularly if your lawnmower has an electric start. During storage, batteries can slowly discharge, and if they fall below a certain voltage, they won’t have enough power to crank the engine. This issue is exacerbated in cold climates, where battery performance tends to decrease even further.
How can I tell if the fuel is the problem?
The easiest way to check is by smelling the fuel in the tank. Fresh gasoline has a distinct, sharp odor, while stale fuel often smells varnish-like, sour, or even has a noticeably different color. If you suspect stale fuel, you can also try draining a small amount into a clear container and observe it for sediment or discoloration.
Another indication of stale fuel problems is difficulty pulling the starter cord or a weak engine sound. Even if the engine turns over, it might sputter or struggle to stay running. Additionally, you might notice that the fuel filter is clogged or has a dark, gummy residue on it, indicating degraded fuel has passed through the system.
What should I do if the fuel is stale?
The first step is to drain all the old fuel from the tank. Disconnect the fuel line from the carburetor (after clamping it shut if necessary to prevent further fuel spillage) and allow the old fuel to flow into a suitable container for proper disposal at a recycling center. Ensure you are working in a well-ventilated area away from any sources of ignition.
Next, you’ll likely need to clean or replace the carburetor. Carburetor cleaner sprays can help dissolve gum and varnish deposits, but if the carburetor is severely clogged, it may need to be disassembled and thoroughly cleaned or replaced entirely. Consider also replacing the fuel filter and fuel lines if they appear to be compromised.
How do I check the spark plug?
Start by disconnecting the spark plug wire. Then, carefully remove the spark plug using a spark plug wrench. Inspect the spark plug for any signs of damage, such as cracks, carbon buildup, or a worn electrode. A healthy spark plug should have a clean, light brown or gray color.
To test if the spark plug is functioning correctly, reconnect the spark plug wire and hold the spark plug against a metal part of the engine while pulling the starter cord. You should see a strong, blue spark jumping across the gap. If there’s no spark or the spark is weak and yellow, the spark plug needs to be replaced.
What if the air filter is clogged?
A clogged air filter restricts airflow to the engine, leading to a rich fuel mixture (too much fuel and not enough air). This can make the engine difficult to start and cause it to run poorly. The severity of the impact depends on how obstructed the filter is.
To check the air filter, remove it from its housing. If it’s a paper filter, inspect it for dirt, debris, and damage. If it’s a foam filter, check for saturation with oil or dirt. Clean a paper filter by gently tapping it against a hard surface to dislodge loose debris or replace it. Wash a foam filter with mild soap and water, allow it to dry completely, and then lightly oil it before reinstalling.
How do I check the oil level?
Locate the oil dipstick on the lawnmower engine, usually indicated by a symbol or marking. Remove the dipstick, wipe it clean with a cloth, and then reinsert it fully. Remove it again to check the oil level.
The oil level should be between the “min” and “max” markings on the dipstick. If the oil level is low, add the correct type of oil, as specified in your lawnmower’s manual, until it reaches the proper level. Never overfill the oil, as this can also cause problems.
What can I do to prevent this from happening again?
Before storing your lawnmower for an extended period, stabilize the fuel with a fuel stabilizer additive. This will help prevent the fuel from breaking down and forming deposits in the carburetor. Alternatively, completely drain the fuel tank and run the engine until it stalls to ensure there’s no fuel left in the carburetor.
Consider removing the spark plug and adding a small amount of engine oil into the cylinder before storage. Pull the starter cord a few times to distribute the oil, which helps prevent rust and corrosion. Disconnect the spark plug wire and store the lawnmower in a dry, sheltered location to protect it from the elements.