Bad gas in a lawn mower is a common problem that can lead to frustrating engine issues, leaving your lawn looking less than perfect. Whether your mower is sputtering, refusing to start, or emitting strange fumes, understanding the cause of bad gas and knowing how to fix it can save you time, money, and the aggravation of a poorly maintained lawn. This comprehensive guide will walk you through the steps to identify and resolve gas-related problems in your lawn mower, ensuring your equipment runs smoothly and efficiently for years to come.
Understanding the Problem: What is “Bad Gas?”
“Bad gas” in lawn mower terms doesn’t necessarily mean the gasoline is inherently defective when you purchase it. Instead, it refers to gasoline that has degraded over time or has been contaminated, rendering it unsuitable for use in your lawn mower’s engine. Several factors contribute to this degradation, making it essential to understand the chemistry and storage of gasoline.
The Science Behind Gasoline Degradation
Gasoline is a complex mixture of hydrocarbons. These hydrocarbons are susceptible to oxidation and evaporation when exposed to air. Over time, this process leads to the formation of gum and varnish deposits that can clog fuel lines, carburetors, and other critical engine components. Ethanol, often added to gasoline as an oxygenate and octane enhancer, can exacerbate this problem. Ethanol attracts water, which can lead to phase separation, where the ethanol and water separate from the gasoline, creating a corrosive mixture that damages engine parts.
Recognizing the Symptoms of Bad Gas
Identifying the symptoms of bad gas early can prevent significant engine damage. Common signs include:
- Difficulty starting the engine: The engine may crank but fail to ignite or start only after repeated attempts.
- Rough idling: The engine may idle unevenly or stall frequently.
- Loss of power: The mower may struggle to cut grass, especially in thicker patches.
- Sputtering or misfiring: The engine may sputter or misfire during operation.
- Unusual exhaust fumes: The exhaust may have a strong, sour, or pungent odor.
- Visible debris in the fuel tank: You might notice sediment or discoloration in the gasoline.
Steps to Fix Bad Gas in Your Lawn Mower
Once you suspect bad gas is the culprit behind your lawn mower’s woes, it’s time to take action. Follow these steps to diagnose and rectify the problem.
Step 1: Emptying the Fuel Tank
The first step is to remove the old, degraded gasoline from the fuel tank.
- Safety First: Always work in a well-ventilated area, away from open flames or sparks. Disconnect the spark plug wire to prevent accidental starting.
- Siphoning the Gas: Use a siphon pump to carefully remove the gas from the tank. Avoid using your mouth to start the siphon.
- Proper Disposal: Dispose of the old gasoline responsibly at a local recycling center or hazardous waste collection facility. Never pour it down drains or onto the ground.
Step 2: Cleaning the Fuel System
After emptying the tank, cleaning the fuel system is crucial to remove any residual gum, varnish, or water.
Cleaning the Fuel Tank
- Rinsing: Rinse the fuel tank with a small amount of fresh gasoline. Swirl it around to dislodge any remaining debris.
- Drying: Empty the tank completely and allow it to air dry.
Cleaning the Fuel Lines
- Disconnecting: Disconnect the fuel lines from the fuel tank and carburetor.
- Blowing Out Debris: Use compressed air to blow out any debris or obstructions in the fuel lines. You can also use carburetor cleaner to dissolve stubborn deposits.
- Reconnecting: Reconnect the fuel lines securely.
Cleaning or Replacing the Fuel Filter
The fuel filter prevents debris from reaching the carburetor.
- Locating the Filter: Identify the fuel filter, usually located in the fuel line between the tank and the carburetor.
- Inspecting the Filter: Examine the filter for clogs or damage.
- Cleaning or Replacing: If the filter is cleanable (some are), clean it with carburetor cleaner. Otherwise, replace it with a new filter.
Step 3: Addressing the Carburetor
The carburetor mixes air and fuel to create the combustion mixture. It is highly susceptible to clogs from bad gas.
Understanding Carburetor Function
The carburetor regulates the amount of fuel entering the engine based on throttle position. Small jets and passages within the carburetor can easily become clogged, disrupting the fuel-air mixture.
Cleaning the Carburetor
- External Cleaning: Start by spraying the exterior of the carburetor with carburetor cleaner to remove dirt and grime.
- Internal Cleaning (If Necessary): If the engine still runs poorly after cleaning the fuel tank and lines, you may need to disassemble and clean the carburetor internally. This is a more complex task that may require a repair manual or online tutorial specific to your mower model.
- Disassembly: Carefully disassemble the carburetor, noting the position of each component.
- Cleaning the Jets: Use carburetor cleaner and small wires or carburetor cleaning tools to clean the jets and passages.
- Reassembly: Reassemble the carburetor, ensuring all components are correctly positioned.
Step 4: Using Fresh Fuel and Fuel Stabilizer
Once the fuel system is clean, it’s time to introduce fresh gasoline.
Choosing the Right Fuel
- Octane Rating: Use the octane rating recommended in your lawn mower’s owner’s manual. Most lawn mowers require regular unleaded gasoline (87 octane).
- Ethanol Content: Opt for gasoline with the lowest possible ethanol content. Ethanol-free gasoline is ideal, but if unavailable, use gasoline with no more than 10% ethanol (E10).
Adding Fuel Stabilizer
Fuel stabilizer prevents gasoline from degrading quickly.
- Dosage: Add fuel stabilizer to the gasoline according to the manufacturer’s instructions.
- Mixing: Mix the fuel stabilizer thoroughly with the gasoline.
Filling the Tank
- Pour Carefully: Pour the fresh gasoline into the fuel tank, avoiding spills.
- Check for Leaks: After filling the tank, check for any fuel leaks.
Step 5: Starting and Testing the Engine
With fresh fuel in the system, it’s time to start the engine and assess the results.
- Reconnecting the Spark Plug Wire: Reconnect the spark plug wire.
- Starting the Engine: Follow the starting procedure outlined in your lawn mower’s owner’s manual.
- Observing Performance: Pay attention to how the engine starts, idles, and runs. If the engine still runs poorly, you may need to revisit the carburetor cleaning process or consult a professional mechanic.
Preventing Future Problems with Gasoline
Preventing bad gas from forming in the first place is the best way to ensure your lawn mower starts reliably and runs smoothly.
Proper Fuel Storage Techniques
- Using Approved Containers: Store gasoline in approved, tightly sealed containers.
- Location: Store gasoline in a cool, dry, well-ventilated place, away from direct sunlight and heat sources.
- Avoid Prolonged Storage: Purchase gasoline in quantities that you will use within a reasonable timeframe (typically within 30 days).
Regular Maintenance Practices
- Draining Fuel Before Storage: Before storing your lawn mower for the winter, drain the fuel tank and run the engine until it stalls to remove any remaining fuel from the carburetor.
- Using Fuel Stabilizer Year-Round: Add fuel stabilizer to every tank of gasoline, even during the mowing season, to prolong its shelf life.
- Regular Engine Tune-Ups: Schedule regular engine tune-ups, including spark plug replacement, air filter cleaning, and carburetor adjustments, to keep your lawn mower running optimally.
Dealing with Ethanol in Gasoline
Ethanol can cause significant problems in small engines.
- Ethanol-Free Gasoline: Whenever possible, use ethanol-free gasoline, especially for long-term storage.
- Ethanol-Resistant Components: Consider replacing fuel lines and other rubber components with ethanol-resistant alternatives.
- Fuel Stabilizers with Ethanol Protection: Use fuel stabilizers specifically formulated to protect against the harmful effects of ethanol.
By understanding the causes of bad gas and implementing these preventative measures, you can minimize fuel-related problems and keep your lawn mower running smoothly for years to come. Proper fuel management is essential for the longevity and performance of your lawn mower. Always prioritize safety when handling gasoline and consult a professional if you are unsure about any aspect of lawn mower maintenance.
What are the common symptoms of bad gas in a lawn mower?
Several symptoms can indicate that the gasoline in your lawn mower has gone bad. You might experience difficulty starting the engine, or it may start but then stall shortly afterward. The engine could also run roughly, sputter intermittently, or lack power when cutting the grass, even on seemingly easy terrain.
Another telltale sign is the presence of a distinct, sour smell emanating from the fuel tank or exhaust. You might also notice dark, gummy deposits inside the fuel tank or carburetor. These deposits are a result of the gasoline breaking down and oxidizing, leaving behind residue that can clog essential components.
How long does gasoline typically last in a lawn mower?
Unstabilized gasoline typically lasts only about 3-6 months before it begins to degrade and lose its effectiveness. This timeframe can be even shorter if the gasoline is exposed to air, moisture, or extreme temperatures. The ethanol found in most gasoline blends attracts water, which accelerates the degradation process and can lead to corrosion in the fuel system.
Adding a fuel stabilizer to your gasoline can significantly extend its lifespan, often up to 12-24 months. The stabilizer prevents the gasoline from oxidizing and forming harmful deposits. However, even with stabilizer, it’s best practice to use gasoline within a year and avoid storing it for extended periods, especially during the off-season.
What is fuel stabilizer and how does it help prevent bad gas?
Fuel stabilizer is an additive designed to prevent gasoline from breaking down and degrading over time. It works by inhibiting the oxidation process, which is the primary cause of gasoline going bad. Fuel stabilizers also contain detergents that help keep the fuel system clean, preventing the formation of gum and varnish deposits that can clog carburetor jets and fuel lines.
By adding fuel stabilizer to your gasoline, especially before storing your lawn mower for the winter, you can protect the fuel system from corrosion and ensure that the engine starts easily when you’re ready to use it again. Always follow the manufacturer’s instructions on the fuel stabilizer bottle for the correct dosage.
How do I properly dispose of old or bad gasoline?
Proper disposal of old gasoline is crucial for environmental safety and compliance with local regulations. Never pour old gasoline down the drain, into the sewer, or onto the ground. Contact your local waste management authority or fire department to find out about designated collection sites or household hazardous waste programs in your area.
Many auto parts stores and recycling centers also accept old gasoline for disposal. If you have a small amount of gasoline, you might be able to mix it with fresh gasoline in your car’s fuel tank, but only if it’s a very small proportion (e.g., a few ounces in a full tank). Always handle gasoline with care and store it in a sealed, approved container until you can dispose of it properly.
What are the steps to drain bad gas from a lawn mower?
First, ensure the engine is cool and the lawn mower is turned off. Disconnect the spark plug wire to prevent accidental starting. Locate the fuel shut-off valve, if your mower has one, and close it. Position a fuel-safe container beneath the carburetor or fuel line, depending on your mower’s design, to catch the gasoline.
If your mower has a drain plug on the carburetor bowl, loosen it carefully to allow the gasoline to drain into the container. If there’s no drain plug, you may need to disconnect the fuel line at the carburetor and let the gasoline flow out. Once the fuel tank is empty, properly dispose of the old gasoline according to local regulations.
How do I clean the carburetor after draining bad gas?
After draining the old gasoline, cleaning the carburetor is often necessary to remove any remaining residue or varnish. Remove the carburetor from the engine, taking careful note of how all the parts are connected. Disassemble the carburetor, referring to your lawn mower’s manual or online resources for guidance.
Use carburetor cleaner spray to thoroughly clean all the carburetor parts, including the jets, float bowl, and needle valve. Pay particular attention to any clogged orifices. Reassemble the carburetor carefully, ensuring all parts are properly seated. Reinstall the carburetor on the engine and test the lawn mower to see if it starts and runs smoothly. You may need to adjust the carburetor settings for optimal performance.
How can I prevent gas from going bad in my lawn mower in the future?
The most effective way to prevent gasoline from going bad is to use a fuel stabilizer every time you fill your gas can. Add the stabilizer to the gasoline according to the manufacturer’s instructions and mix it thoroughly. This will help keep the gasoline fresh and prevent the formation of harmful deposits.
Another preventative measure is to only purchase the amount of gasoline you expect to use within a reasonable timeframe, ideally a month or two. Avoid storing large quantities of gasoline for extended periods. When storing your lawn mower for the off-season, drain the fuel tank completely or add a fuel stabilizer to a full tank to minimize air exposure and prevent condensation.