Old, stale gasoline is a common culprit when your mower refuses to run properly. If you’re wondering how to get old gas out of lawn mower, you’re in the right place. This guide provides clear, step-by-step instructions to safely remove that bad fuel and get your equipment running smoothly again.
Leaving gas in your mower over the winter or for extended periods leads to problems. The fuel breaks down, forms varnish and gum, and can clog the entire fuel system. Dealing with it promptly saves you time and money on repairs.
How To Get Old Gas Out Of Lawn Mower
The core process of removing old fuel involves a few key steps. Safety is the absolute first priority. You’ll need some basic tools and a plan for disposing of the gasoline responsibly. Let’s break it down from start to finish.
Essential Safety Precautions Before You Start
Gasoline is highly flammable and its fumes are dangerous. Always work in a well-ventilated outdoor area, away from any open flames, sparks, or heat sources. Do not smoke. Have a fire extinguisher rated for flammable liquids nearby just in case.
Wear appropriate personal protective equipment. This includes safety glasses to protect your eyes from splashes and chemical-resistant gloves. Gasoline can irritate your skin and is harmful if absorbed.
Allow the engine to cool completely if the mower has been running. A hot engine presents a significant fire risk. Position the mower on a flat, level surface to prevent tipping and to ensure you can properly drain the fuel tank.
Tools And Materials You Will Need
Gathering your supplies before you begin makes the job smoother. You likely have most of these items already.
- A siphon pump (hand-operated or battery-powered) or a turkey baster dedicated to this task.
- A clean, approved fuel container for storing the old gas. Do not use milk jugs or glass containers.
- Several rags or shop towels for spills.
- A set of basic wrenches or sockets.
- A flat-head and Phillips screwdriver.
- Needle-nose pliers.
- Fresh, high-quality gasoline (and possibly fuel stabilizer for the future).
Step-by-Step Drainage Methods
There are three primary methods to remove old gasoline. The best one for you depends on your mower’s design and your comfort level.
Method 1: Siphoning From the Fuel Tank
This is the simplest and most common method for riders and mowers with accessible tanks. First, locate the fuel tank cap and remove it. Insert the tube of your siphon pump into the tank, ensuring it reaches the bottom.
Place your approved disposal container on the ground, lower than the mower’s fuel tank. Operate the siphon pump according to its instructions to start the flow. Continue until no more fuel comes out. Use a rag to clean up any drips around the tank opening.
Method 2: Draining the Carburetor Bowl
If siphoning doesn’t get all the fuel, or if you need to clean the carburetor, this step is crucial. The carburetor is usually a small, metal box attached to the engine. Locate the carburetor bowl on the bottom; it often has a small drain screw or nut.
Place your container underneath. Using the correct size wrench, carefully loosen the drain screw. Allow all the fuel to drain out, then tighten the screw securely. Be cautious, as this screw can be delicate and prone to stripping.
Method 3: Disconnecting the Fuel Line
For some mowers, directly accessing the fuel line is most effective. Find the flexible fuel line running from the gas tank to the carburetor. Use pliers to loosen the clamp securing it, then gently pull the hose off the carburetor nipple.
Direct the open end of the fuel line into your container. You may need to open the gas tank cap to allow air in and start the flow. Once drained, reattach the hose and secure the clamp. Check for any leaks when you add fresh gas later.
How To Dispose Of Old Gasoline Properly
Never pour old gasoline down a drain, onto the ground, or into regular trash. It is hazardous waste and must be handled as such. Contact your local waste management authority or a nearby auto parts store. Many communities have designated hazardous waste collection days or permanent facilities.
Store the old gas in its approved, clearly labeled container until you can dispose of it. Keep it away from children, pets, and any living areas. Mixing it with fresh gas is not a reliable solution and can ruin the new fuel.
Cleaning The Fuel System After Drainage
Simply removing the old gas isn’t always enough. Residual varnish and gum can cling to the tank and carburetor. For a thorough clean, consider using a fuel system cleaner. Add a recommended dose to a small amount of fresh gas in the tank, run the engine for a few minutes, then drain it again to flush the system.
In severe cases where the mower still won’t start, the carburetor jet may be clogged. This might require a complete carburetor cleaning or rebuild, which involves disassembly and using carburetor cleaner spray. If you’re not comfortable with this, seek help from a small engine repair shop.
Preventing Old Gas Problems In The Future
The best solution is to avoid the problem altogether. With good habits, you’ll rarely need to drain old gas again.
- Use a Fuel Stabilizer: Add a quality stabilizer to every gallon of fresh gas, especially the last tank of the mowing season. It prevents the fuel from breaking down for up to 24 months.
- Run the Engine Dry: At the end of the season, either run the mower until it stalls from an empty tank, or use the siphon to remove all fuel from the tank and carburetor.
- Use Fresh Gasoline: Buy gasoline in smaller quantities that you will use within 30 days. Older gas from a gas station can already be starting to degrade.
- Store Your Mower Correctly: Keep it in a cool, dry place away from direct sunlight, which accelerates fuel evaporation and degradation.
Troubleshooting After Removing Old Gas
Even after draining and adding fresh fuel, you might encounter issues. Here’s how to address common problems.
Lawn Mower Still Won’t Start
If the engine doesn’t turn over, check your spark plug. Old gas can foul the plug with deposits. Remove it, clean the electrode with a wire brush, check the gap, and try again. A completely new spark plug is a cheap and effective fix.
Ensure the fuel valve (if your mower has one) is in the “On” position. Check that the air filter isn’t clogged, as a dirty filter restricts the air needed for combustion. A quick clean or replacement can make a big difference.
Engine Runs Rough or Sputters
This often indicates that some residue remains in the carburetor or fuel line. The pilot jet or main jet might be partially blocked. You may need to repeat the carburetor bowl draining procedure or use a stronger fuel system cleaner designed to dissolve stubborn deposits.
Also, verify that you’re using the correct type and octane of gasoline recommended by your mower’s manufacturer. Using the wrong fuel can cause performance issues.
Frequently Asked Questions
How Long Does It Take For Gas To Go Bad In A Lawn Mower?
Gasoline can begin to degrade in as little as 30 days. Within 3-6 months, it often loses enough volatility to cause starting problems. After a year, it’s usually too stale to use and will likely damage your mower’s fuel system.
Can You Mix Old Gas With New Gas In A Lawn Mower?
It is not recommended. The old gas has already broken down and will contaminate the fresh fuel, reducing its effectiveness. The best practice is to always remove as much old gas as possible before adding new fuel. Dilution is not a reliable solution.
What Are The Symptoms Of Bad Gas In A Lawn Mower?
Common signs include difficulty starting, the engine stalling shortly after starting, rough idling, loss of power while mowing, and the engine not reaching full operating speed. You might also smell a sour, varnish-like odor from the gas tank.
Is It Necessary To Drain Gas From A Lawn Mower For Winter?
Yes, it is highly advisable. The two recommended strategies are to either add a fuel stabilizer to a full tank and run the engine for 5 minutes to circulate it, or to completely drain the tank and carburetor bowl. Leaving untreated gas in the mower over winter is a leading cause of springtime starting failures.
Where Can I Take Old Gas For Disposal?
Check with your local government’s sanitation or public works department for hazardous waste collection sites. Many auto repair shops and parts stores also accept old gasoline for a small fee. Never dispose of it improperly, as it poses serious environmental and fire risks.