You’re ready to tackle the lawn, but when you start your mower, you’re met with a plume of unburnt gasoline spewing from the exhaust. Not only is this concerning, but it also signals a problem with your mower’s engine that needs attention. This article will delve into the common reasons why gas might be coming out of your lawn mower exhaust, helping you understand the problem and take the necessary steps to fix it.
In simple terms, gas coming out of the exhaust means your mower isn’t burning fuel efficiently. This could be due to a variety of factors, ranging from a simple carburetor adjustment to a more serious engine issue. We’ll explore the most likely culprits, from fuel issues to ignition problems, and provide practical troubleshooting tips to help you get your lawn mower running smoothly again.
Fuel-Related Issues
Fuel problems are often the root cause of unburnt gasoline exiting the exhaust. Here’s a breakdown of the most common fuel-related issues:
1. Carburetor Problems
The carburetor is responsible for mixing air and fuel in the correct ratio for combustion. If the carburetor is dirty, clogged, or not properly adjusted, it can lead to a rich fuel mixture, meaning there’s too much fuel and not enough air. This excess fuel isn’t fully burned, resulting in gas coming out of the exhaust.
Symptoms of a Carburetor Problem
- Difficult Starting: The engine might struggle to start or stall frequently.
- Black Smoke: A thick black smoke from the exhaust indicates a rich fuel mixture.
- Rough Running: The engine might run unevenly or hesitate.
- Fuel Leaks: You may notice fuel leaking from the carburetor.
Troubleshooting and Repairing Carburetor Issues
- Clean the carburetor: Remove the carburetor and thoroughly clean it with a carburetor cleaner.
- Adjust the carburetor: If the carburetor is adjustable, you might need to fine-tune the mixture. Consult your owner’s manual for specific instructions.
- Replace the carburetor: If the carburetor is severely damaged or beyond repair, a replacement might be necessary.
2. Fuel Quality and Storage
The quality and freshness of your fuel can also contribute to engine problems.
Old Fuel
Old fuel can degrade and form deposits that clog the carburetor and fuel lines, causing an inefficient fuel mixture.
Ethanol Content
Ethanol, a common additive in gasoline, attracts moisture. When stored for long periods, the ethanol absorbs moisture, leading to phase separation, where the gasoline and water separate. This can cause carburetor and fuel line issues.
Fuel Storage and Handling
- Use fresh, quality gasoline.
- Avoid using gasoline older than 3 months.
- Store fuel in clean, airtight containers.
- Add fuel stabilizer to prevent degradation.
Ignition System Problems
The ignition system is responsible for creating the spark that ignites the air-fuel mixture. If the ignition system isn’t working properly, the mixture might not ignite fully, leading to unburnt fuel being expelled from the exhaust.
1. Spark Plug Issues
The spark plug is the key component in the ignition system. A worn-out or fouled spark plug can fail to ignite the fuel mixture properly.
Symptoms of Spark Plug Problems
- Difficulty Starting: The engine might struggle to start or not start at all.
- Misfires: The engine might run rough or misfire.
- Black Smoke: Excessive black smoke can indicate a fouled spark plug.
Troubleshooting and Replacing Spark Plugs
- Inspect the spark plug: Remove the spark plug and check for wear, fouling, or damage.
- Replace the spark plug: If the spark plug is worn or fouled, replace it with a new one of the correct type.
2. Ignition Coil Failure
The ignition coil generates the high voltage needed to create a spark at the spark plug. If the ignition coil fails, it can prevent the spark plug from igniting the fuel.
Symptoms of Ignition Coil Failure
- No Spark: If the coil fails completely, there will be no spark at the spark plug.
- Misfires: The engine might run rough or misfire.
Troubleshooting and Replacing the Ignition Coil
- Test the ignition coil: Use a multimeter to test the coil’s resistance.
- Replace the ignition coil: If the coil is faulty, replace it with a new one.
Other Potential Causes
While fuel and ignition issues are the most common culprits, other factors can contribute to gas coming out of the exhaust:
1. Air Filter Clogging
A clogged air filter restricts airflow to the engine, resulting in a rich fuel mixture.
2. Engine Compression Loss
A loss of engine compression can prevent the fuel from burning efficiently.
3. Valve Problems
Damaged or improperly adjusted valves can also hinder combustion.
Diagnosing the Problem: Steps to Take
Here’s a step-by-step approach to diagnosing the problem:
- Inspect the Spark Plug: Start by removing the spark plug and checking its condition. Look for signs of wear, fouling, or damage.
- Check the Air Filter: Inspect the air filter and make sure it’s clean.
- Examine the Carburetor: If the spark plug and air filter are in good condition, the carburetor might be the culprit.
- Test the Ignition Coil: If the carburetor is clean and adjusted properly, test the ignition coil to ensure it’s functioning.
Getting Help from a Professional
If you’re unable to diagnose and fix the problem yourself, consult a qualified lawn mower repair technician. They have the experience and tools to pinpoint the issue and perform the necessary repairs.
Conclusion
Unburnt gasoline coming out of your lawn mower exhaust isn’t a problem to ignore. It indicates that your engine isn’t burning fuel efficiently, potentially due to issues with the carburetor, ignition system, or other factors. By understanding the common causes and troubleshooting steps outlined in this article, you can often identify and resolve the problem yourself. If you’re unable to do so, seek help from a professional technician for a proper diagnosis and repair.
FAQ
Q1: What is the most common reason gas comes out of a lawn mower exhaust?
A: The most common reason gas comes out of a lawn mower exhaust is a carburetor issue. The carburetor is responsible for mixing air and fuel in the correct proportions for combustion. If the carburetor is dirty, clogged, or malfunctioning, it can lead to an over-rich fuel mixture, which results in unburnt fuel being expelled through the exhaust. This can also be a sign of a leaking fuel line or a clogged fuel filter, which restrict fuel flow and disrupt the air-fuel mixture.
Q2: Can a faulty spark plug cause gas to come out of the exhaust?
A: Yes, a faulty spark plug can contribute to gas coming out of the exhaust. A worn-out or damaged spark plug can fail to ignite the air-fuel mixture efficiently, leading to incomplete combustion. This can result in unburnt fuel being expelled through the exhaust. If the spark plug is too old or fouled, it may not be able to generate a strong enough spark to ignite the fuel properly, leading to this issue.
Q3: Can a clogged air filter cause gas to come out of the exhaust?
A: Yes, a clogged air filter can cause gas to come out of the exhaust. The air filter prevents dirt and debris from entering the engine, but when it becomes clogged, it restricts airflow. This leads to a richer fuel mixture, as the engine compensates by supplying more fuel to maintain the proper air-fuel ratio. This can result in unburnt fuel being expelled through the exhaust.
Q4: How do I troubleshoot why gas is coming out of the exhaust?
A: Start by inspecting the air filter, spark plug, and fuel lines. If the air filter is dirty, replace it. If the spark plug is worn or fouled, replace it. Check the fuel lines for leaks or kinks. If you find any issues, address them before proceeding. If these are all in good condition, then it’s likely a carburetor issue, which may require professional attention.
Q5: How do I clean the carburetor?
A: Cleaning the carburetor can be done by a professional mechanic or by yourself with the right tools and knowledge. You’ll need a carburetor cleaner, a small brush, and a screwdriver set. It’s important to disconnect the fuel line and battery before starting. Disassemble the carburetor and clean the internal parts with the carburetor cleaner. Make sure to thoroughly clean and dry all parts before reassembling.
Q6: Is it dangerous to run my lawnmower with gas coming out of the exhaust?
A: Yes, it’s dangerous to run your lawnmower with gas coming out of the exhaust. Unburnt fuel in the exhaust can create a fire hazard, especially if it ignites. Additionally, the excess fuel can damage the engine over time, leading to further problems.
Q7: What should I do if I suspect a carburetor issue?
A: If you suspect a carburetor issue, it’s best to take your lawnmower to a qualified mechanic for diagnosis and repair. They have the tools and expertise to properly diagnose and address the problem, ensuring your lawnmower is safe and efficient to operate.