Gasoline, the lifeblood of our lawn mowers, is a surprisingly fickle substance. While it seems like it should last indefinitely in the tank, the reality is quite different. The question of whether old gas can prevent your lawn mower from starting is a resounding “yes,” and understanding why is crucial for maintaining your mower and avoiding frustrating starting problems.
The Deterioration of Gasoline: A Chemical Breakdown
Gasoline isn’t just one single compound; it’s a complex mixture of hydrocarbons. Over time, these hydrocarbons begin to break down and oxidize, leading to a series of chemical changes that negatively impact the fuel’s properties.
Oxidation: The Rust of Gasoline
Oxidation is a major culprit in gasoline degradation. When gasoline is exposed to oxygen, a chemical reaction occurs that alters its composition. This process is accelerated by heat and sunlight, both of which are common during lawn mowing season. The oxidation process creates gums and varnishes, which are sticky residues that can clog fuel lines, carburetors, and other critical engine components.
Evaporation: Losing the Light Ends
Gasoline contains volatile components, often referred to as “light ends,” that are essential for easy starting. These components evaporate over time, especially in poorly sealed containers or fuel tanks. As the light ends evaporate, the remaining gasoline becomes less volatile, making it harder to ignite and start the engine.
Water Absorption: A Recipe for Corrosion
Modern gasoline often contains ethanol, an alcohol that attracts and absorbs water. While ethanol can improve octane levels and reduce emissions, it also presents a significant problem for small engines. Water contamination can lead to corrosion in the fuel system, further hindering performance. The water can also separate from the gasoline, creating a layer of water at the bottom of the tank that the engine can’t use. This phase separation is particularly problematic in older engines not designed to handle high ethanol content.
Identifying Old Gasoline: Signs and Symptoms
Knowing how to identify old gasoline is essential for preventing starting problems. Several telltale signs can indicate that your fuel has gone bad.
Visual Inspection: Color and Clarity
Fresh gasoline typically has a clear, slightly yellowish appearance. Old gasoline may darken, becoming amber or even brown. It might also appear cloudy or murky, indicating contamination or degradation. A visual inspection is often the first line of defense against using bad fuel.
The Smell Test: A Sour Aroma
Fresh gasoline has a distinct, recognizable odor. Old gasoline, on the other hand, may develop a sour, pungent smell, similar to varnish or turpentine. This change in odor is a strong indicator that the fuel has deteriorated and should not be used.
Engine Performance Issues: Stalling and Hesitation
If you’ve used old gasoline and managed to start your lawn mower, you may experience noticeable performance issues. These can include difficult starting, rough idling, stalling, hesitation during acceleration, and a general lack of power. These symptoms are often a result of clogged fuel lines and carburetors caused by the gums and varnishes in the old fuel.
The Impact on Your Lawn Mower: A Chain Reaction
Using old gasoline in your lawn mower can lead to a cascade of problems, affecting various components and ultimately preventing the engine from starting.
Clogged Carburetor: The Primary Suspect
The carburetor is responsible for mixing air and fuel in the correct proportions for combustion. The gums and varnishes formed by old gasoline can clog the tiny passages and jets within the carburetor, disrupting the fuel-air mixture and preventing the engine from starting or running properly. A clogged carburetor is one of the most common reasons why lawn mowers fail to start after sitting for a while.
Fuel Line Blockages: Cutting Off the Supply
Fuel lines carry gasoline from the fuel tank to the carburetor. Old gasoline can leave deposits in these lines, causing blockages that restrict or completely stop the flow of fuel. These blockages prevent the engine from receiving the fuel it needs to start and run.
Valve Issues: Sticky Situations
In some cases, the gums and varnishes from old gasoline can accumulate on the valves, causing them to stick or not seal properly. This can lead to reduced compression and poor engine performance, making it difficult or impossible to start the engine.
Damage to Fuel Tank: Corrosion Concerns
The presence of water and ethanol in old gasoline can lead to corrosion in the fuel tank, particularly in metal tanks. This corrosion can create rust particles that further contaminate the fuel system and clog fuel lines and filters.
Prevention is Key: Maintaining Your Fuel and Mower
Preventing gasoline from going bad is far easier and less expensive than dealing with the consequences of using old fuel. Simple maintenance practices can significantly extend the life of your gasoline and ensure that your lawn mower starts reliably.
Using Fuel Stabilizer: A Protective Shield
Fuel stabilizer is a chemical additive that prevents gasoline from oxidizing and degrading. Adding fuel stabilizer to your gasoline before storing it for an extended period can significantly prolong its lifespan. Fuel stabilizers work by inhibiting the formation of gums and varnishes and preventing the separation of water from the gasoline.
Proper Storage: Cool, Dark, and Sealed
Store gasoline in a cool, dark, and dry place, away from direct sunlight and heat. Use an approved gasoline container that is tightly sealed to prevent evaporation and contamination. Avoid storing gasoline in clear containers, as sunlight can accelerate the degradation process.
Draining the Fuel Tank: The Empty Option
If you’re not planning to use your lawn mower for an extended period, such as during the off-season, consider draining the fuel tank completely. This prevents the gasoline from sitting in the tank and deteriorating over time. Be sure to run the engine until it stalls to ensure that the carburetor is also empty.
Regular Engine Maintenance: A Stitch in Time
Regular engine maintenance, including changing the air filter, spark plug, and oil, can help keep your lawn mower running smoothly and prevent problems related to old gasoline. A clean engine is less susceptible to the negative effects of degraded fuel.
Reviving Your Mower: Solutions for Old Gas Problems
If you suspect that your lawn mower is suffering from the effects of old gasoline, there are several steps you can take to try to revive it.
Draining and Replacing the Fuel: The Obvious Choice
The first and most obvious step is to drain the old gasoline from the fuel tank and replace it with fresh fuel. Dispose of the old gasoline properly at a designated recycling center or hazardous waste disposal facility.
Cleaning the Carburetor: A Detailed Task
If simply replacing the fuel doesn’t solve the problem, you may need to clean the carburetor. This can be done by removing the carburetor and disassembling it to clean the jets and passages with carburetor cleaner. Alternatively, you can try using a carburetor cleaner additive in the fuel tank, although this may not be as effective as a thorough cleaning.
Replacing Fuel Lines and Filters: A Preventive Measure
If the fuel lines are clogged or cracked, or if the fuel filter is dirty, replace them. This will ensure that the engine receives a clean and consistent supply of fuel.
Seeking Professional Help: When to Call an Expert
If you’ve tried the above steps and your lawn mower still won’t start, it’s time to seek professional help from a qualified mechanic. They have the tools and expertise to diagnose and repair more complex engine problems.
The Final Verdict: Old Gas is a No-Go
In conclusion, old gasoline can absolutely prevent your lawn mower from starting. The degradation of gasoline over time leads to the formation of gums, varnishes, and water, which can clog fuel lines, carburetors, and other engine components. Prevention is the best approach, so use fuel stabilizer, store gasoline properly, and perform regular engine maintenance. If your lawn mower is already suffering from the effects of old gasoline, try draining and replacing the fuel, cleaning the carburetor, and replacing fuel lines and filters. If all else fails, seek professional help. By understanding the effects of old gasoline and taking proactive measures, you can keep your lawn mower running smoothly for years to come.
Why does old gas prevent a lawn mower from starting?
Gasoline degrades over time due to oxidation and evaporation. These processes cause the lighter, more volatile compounds that are essential for easy ignition to dissipate. What’s left behind are heavier, gum-like residues and varnish that can clog the carburetor, fuel lines, and other critical components of your lawn mower’s fuel system. This degraded fuel is less combustible and makes it extremely difficult, if not impossible, for the engine to start properly.
The breakdown of gasoline also leads to the formation of water within the fuel system. This water can cause corrosion in the fuel tank and other metal parts, further hindering the flow of fuel and the overall performance of the engine. This contamination often leads to starting problems, rough running, and even engine damage if left unaddressed for extended periods.
How long does gasoline typically last before it goes bad?
Unstabilized gasoline typically begins to degrade noticeably after about 30 days, depending on storage conditions. Warmer temperatures and exposure to air accelerate the degradation process. After 3-6 months, the gasoline may become too stale to reliably start a lawn mower or other small engine.
Proper storage is key to extending the lifespan of gasoline. Using a fuel stabilizer, storing the gas in an airtight container, and keeping it in a cool, dark place can significantly slow down the degradation process. Treated gasoline can potentially remain usable for up to 12 months under optimal storage conditions.
What are the signs that my lawn mower has old gas in it?
If your lawn mower is difficult to start, sputters, runs roughly, or stalls frequently, old gas is a likely culprit. You might also notice a distinct varnish-like smell emanating from the fuel tank or carburetor. In more severe cases, the engine may not start at all.
Visually inspecting the gasoline can also provide clues. Fresh gasoline should be clear and have a characteristic odor. If the gas appears darker than usual, has a cloudy appearance, or contains visible sediments, it’s likely degraded. A gummy or varnish-like residue around the fuel cap or carburetor is another strong indicator.
Can I fix a lawn mower with old gas by simply adding fresh gas?
Adding fresh gas to old gas in the tank may help slightly, but it’s generally not a reliable solution for severe cases of fuel degradation. While the fresh gas might dilute the old fuel and improve its combustibility to some extent, the varnish and gum deposits will likely remain in the system, continuing to cause problems.
For the best results, it’s recommended to completely drain the old gas from the fuel tank, fuel lines, and carburetor. Then, add fresh, stabilized gasoline to the clean system. This will ensure that the engine receives a clean and reliable fuel supply, minimizing the chances of future starting or performance issues.
How do I properly drain old gas from my lawn mower?
First, ensure the engine is cool and the lawn mower is turned off. Disconnect the spark plug wire to prevent accidental starting. Then, locate the fuel shut-off valve (if your mower has one) and close it. Position a suitable container under the carburetor bowl drain plug or the fuel line connection at the carburetor.
Open the drain plug or disconnect the fuel line and allow the old gas to drain completely into the container. Once drained, reconnect the fuel line or close the drain plug securely. Refill the fuel tank with fresh, stabilized gasoline. Properly dispose of the old gasoline at a hazardous waste collection center or recycling facility.
What is a fuel stabilizer and how does it help?
A fuel stabilizer is an additive that slows down the degradation process of gasoline. It works by preventing oxidation and evaporation, which are the primary causes of fuel deterioration. By inhibiting these processes, a fuel stabilizer helps to keep the gasoline fresh and usable for a longer period.
Fuel stabilizers also contain detergents that help to clean and protect the fuel system from varnish and gum deposits. This keeps the carburetor and fuel lines clean, ensuring proper fuel flow and engine performance. Regularly using a fuel stabilizer, especially when storing your lawn mower for extended periods, can significantly reduce the risk of starting problems caused by old gas.
What are some other factors that can prevent a lawn mower from starting, besides old gas?
Beyond old gas, several other factors can prevent a lawn mower from starting. A dirty air filter can restrict airflow to the engine, making it difficult to ignite the fuel mixture. A faulty spark plug can fail to generate the necessary spark to ignite the fuel, preventing combustion.
A clogged carburetor can disrupt the fuel-air mixture, leading to starting issues. Additionally, a low battery (in electric start models), a malfunctioning starter motor, or a problem with the safety interlock switches (e.g., blade engagement lever or seat switch) can also prevent the engine from cranking or starting. Regularly maintaining these components can help ensure reliable starting.