The warm sun is shining, the birds are chirping, and you’re ready to tackle that overgrown lawn. But when you pull the starter cord, your lawn mower sputters, coughs, and dies. Frustration sets in, especially when you’re eager to get the job done. Why won’t your lawn mower keep running? This article will delve into common reasons for a sputtering lawn mower, equipping you with the knowledge to troubleshoot the problem and get your mower back in action.
The culprit behind a lawn mower that won’t stay running is often a combination of factors: a lack of fuel or spark, clogged air filters, fouled spark plugs, or even a faulty carburetor. Understanding these potential problems is the first step towards diagnosing and fixing the issue.
Fuel and Spark: The Essentials for a Running Engine
The most basic requirements for any internal combustion engine, including your lawn mower, are fuel and spark. Without either, the engine will not run. Here’s a quick breakdown:
Fuel: Your lawn mower needs a consistent supply of fuel to burn. If the fuel is old, contaminated, or the fuel lines are blocked, the engine may struggle to start or run.
Spark: The spark plug provides the electrical spark that ignites the fuel-air mixture, initiating combustion. If the spark plug is fouled, damaged, or the spark plug wire is faulty, the spark will be weak or absent, preventing the engine from firing.
Checking Fuel and Spark
**1. Fuel: **
- Examine the fuel tank: Ensure the fuel tank is at least half full.
- Inspect the fuel lines: Look for any cracks, leaks, or blockages in the fuel lines.
- Test the fuel flow: With the fuel tank open, try to squeeze the fuel line to check for fuel flow. If no fuel comes out, the fuel line might be clogged.
- Replace old fuel: If the fuel in the tank is older than a few months, it’s best to drain it and replace it with fresh fuel. Ethanol in gasoline can attract moisture and degrade over time.
**2. Spark: **
- Inspect the spark plug: Remove the spark plug and examine it for wear, carbon build-up, or damage. A healthy spark plug should have a light brown, tan, or gray color.
- Check for spark: Connect the spark plug wire to the spark plug and hold the spark plug against the engine block. Pull the starter cord. You should see a bright blue spark jumping across the gap of the spark plug. If there is no spark, the problem could be a faulty spark plug, wire, or ignition system.
Airflow: Getting the Right Mix
Once you’ve confirmed fuel and spark, the next essential component for your lawn mower is airflow. The engine needs a constant supply of fresh air to mix with the fuel, creating the combustible mixture.
Common Airflow Issues
1. Clogged Air Filter: The air filter prevents dirt and debris from entering the engine, but it can also become clogged over time. A clogged air filter restricts airflow, causing the engine to run poorly or stall.
2. Air Leaks: Cracks or leaks in the air intake manifold or air filter housing can cause air to leak into the engine, disrupting the fuel-air mixture. This can cause the engine to run poorly or stall.
3. Restricted Air Intake: Grass clippings or debris accumulating around the air intake can also restrict airflow.
Cleaning or Replacing the Air Filter
- Inspect the air filter: Remove the air filter and examine it. If it’s heavily soiled, it’s time for a replacement.
- Clean the air filter: If the air filter is just slightly dirty, you can clean it with compressed air or by lightly tapping it to remove dust and debris.
- Replace the air filter: If the air filter is beyond cleaning, replace it with a new, compatible filter.
Carburetor: The Heart of the Engine
The carburetor plays a critical role in mixing fuel and air for the engine. It controls the amount of fuel and air entering the combustion chamber, ensuring the correct fuel-air ratio for optimal performance.
Common Carburetor Problems
1. Clogged Jets: Over time, the carburetor jets can become clogged with dirt, debris, or gum deposits from fuel. This disrupts the fuel flow, leading to engine problems.
2. Dirty or Worn Parts: The carburetor contains several moving parts that can wear down or become dirty. This can affect the carburetor’s ability to mix fuel and air properly.
3. Improper Adjustments: The carburetor has adjustable screws that control the fuel-air mixture. If these screws are improperly adjusted, the engine may run too rich or too lean, leading to performance issues.
Cleaning or Replacing the Carburetor
- Clean the carburetor: If the carburetor is dirty, you can try cleaning it. This involves removing the carburetor from the engine, disassembling it, and cleaning the parts with a carburetor cleaning kit.
- Rebuild or Replace: If the carburetor is severely damaged or worn, it’s best to rebuild it or replace it with a new one.
Other Potential Issues
While the problems above are the most common, other factors could contribute to a lawn mower that won’t stay running:
1. Faulty Ignition System: A faulty ignition coil, ignition module, or wiring can prevent the spark plug from receiving a spark.
2. Stuck Valves: If the valves in the engine are stuck open or closed, the engine won’t run properly.
3. Bad Fuel Pump: A faulty fuel pump can’t deliver fuel to the carburetor, resulting in engine failure.
4. Low Compression: Low compression in the engine cylinder can prevent the fuel-air mixture from igniting properly.
Tips for Preventing Lawn Mower Problems
- Use fresh, clean fuel: Always use fresh, high-quality fuel, and avoid using fuel that’s older than a few months.
- Change the spark plug regularly: Replace the spark plug according to the manufacturer’s recommendations.
- Clean the air filter regularly: Check the air filter for dirt and debris, and clean or replace it as needed.
- Store the mower properly: When not in use, drain the fuel tank and store the mower in a dry, cool place.
- Perform regular maintenance: Follow the manufacturer’s recommended maintenance schedule for your lawn mower, including oil changes, blade sharpening, and carburetor cleaning.
Conclusion
A lawn mower that won’t keep running can be a frustrating problem. However, by understanding the common causes and troubleshooting steps outlined in this article, you can diagnose and fix the problem yourself. Remember to check fuel, spark, airflow, and the carburetor, and don’t hesitate to consult a service manual or a qualified technician if you’re not comfortable with any of the repairs. With a little effort and attention, you can get your lawn mower back in top shape and enjoy a perfectly manicured lawn.
Frequently Asked Questions
1. What are the most common reasons why a lawnmower won’t stay running?
The most common reasons your lawnmower won’t stay running are often related to fuel and spark. A clogged fuel filter, old or bad gas, or a dirty carburetor can prevent fuel from reaching the engine. Additionally, a faulty spark plug, loose spark plug wire, or a malfunctioning ignition coil can all disrupt the spark needed to ignite the fuel.
By inspecting and addressing these components, you can quickly diagnose and fix most common lawnmower running problems.
2. How do I check if the fuel filter is clogged?
To check your fuel filter, locate it in the fuel line between the fuel tank and carburetor. It’s usually a small, cylindrical object. Remove the filter and inspect it for any debris or blockage. If it’s dirty or clogged, replace it with a new one. If the filter is clean, the problem might lie elsewhere.
Remember to use the correct type of fuel filter for your specific lawnmower model. Refer to your owner’s manual for instructions and compatibility.
3. Could old gas be the issue?
Old gas can definitely be the culprit. Gasoline degrades over time, losing its volatility and ability to ignite properly. If your lawnmower has been sitting for a while, drain the old gas and refill with fresh fuel.
You can also add a fuel stabilizer to the gas tank to help prevent the fuel from degrading. This is especially useful for long-term storage.
4. How do I clean the carburetor?
Cleaning the carburetor involves removing it from the engine and disassembling it. Use a carburetor cleaner spray and a small brush to remove any debris or deposits. Pay attention to the small jets and passages within the carburetor.
Remember to carefully reassemble the carburetor and follow any specific instructions from your owner’s manual. If you’re uncomfortable with this task, consult a professional mechanic.
5. How do I check the spark plug?
To check the spark plug, locate it on the engine cylinder. Remove it and inspect the electrode for signs of wear, damage, or fouling. If it appears worn or fouled, replace it with a new one.
You can also test the spark plug by grounding it to a metal surface and cranking the engine. You should see a spark jump across the electrode gap.
6. What if the spark plug wire is loose?
A loose spark plug wire can prevent the spark from reaching the spark plug. Carefully inspect the wire connection at both the spark plug and the ignition coil.
Ensure the wire is securely attached and free from any damage or corrosion. If necessary, tighten the connection or replace the wire if it’s faulty.
7. Could a dead battery be the problem?
While less common, a dead battery can sometimes prevent the engine from starting. Check the battery terminals for corrosion or looseness. If the battery is old or weak, replace it with a new one.
You can also use a jump starter or charge the battery to see if that resolves the issue. If the problem persists, other issues might be preventing the lawnmower from running.