The warm sun is shining, the birds are chirping, and you’re ready to tackle your weekend lawn care. You pull the starter cord on your trusty lawn mower, and you hear the familiar whirring of the engine turning over, but nothing else. The dreaded silence of a lawn mower refusing to start. Frustration sets in, and you find yourself wondering, “Why is my lawn mower turning over but not starting?” This article will guide you through the common culprits behind this perplexing problem, providing troubleshooting steps and tips to get your mower back in action.
In short, a lawn mower that turns over but doesn’t start usually indicates an issue with fuel delivery, spark, or compression. Let’s dive into each of these areas to pinpoint the problem and get your mower running smoothly again.
Fuel System Trouble: Checking the Basics
The first place to look when your lawn mower won’t start is the fuel system. This encompasses everything from the fuel tank to the carburetor, which mixes fuel and air to create a combustible mixture.
1. Fuel: Fresh and Ready to Go
The most common issue preventing your lawn mower from starting is stale or bad fuel. Gasoline can deteriorate over time, especially if it’s been sitting in the tank for a long period.
Here’s how to check the fuel:
- Look for Sediment: Examine the fuel in your tank. If you see any sediment or discoloration, it’s time to replace it.
- Smell the Fuel: Fresh gasoline has a distinct odor. If the fuel smells stale or has a strange odor, it’s likely time to replace it.
If your fuel is stale, drain it completely and replace it with fresh, high-octane gasoline. Always use gasoline that is formulated for small engines. Avoid using ethanol-blended gasoline as it can cause problems with fuel lines and carburetors over time.
2. Fuel Lines: Clear and Unobstructed
Next, check the fuel lines for any blockages or leaks.
- Look for Cracks and Leaks: Inspect the fuel lines for any visible cracks or leaks. If you find any, replace them immediately.
- Ensure Clear Passage: If the lines appear intact, gently blow through them to ensure there are no blockages.
If you find any problems with the fuel lines, replace them with new ones.
3. Carburetor: Clogged or Dirty
The carburetor is the heart of your lawn mower’s fuel system. A dirty or clogged carburetor can prevent fuel from reaching the engine.
Here’s how to diagnose and clean a carburetor:
- Visual Inspection: Look for signs of debris or gunk in the carburetor. If you see anything, it’s time for a cleaning.
- Carb Cleaning Kit: Use a carburetor cleaning kit designed for small engines. This kit usually includes a spray cleaner and a small brush. Follow the instructions on the kit for proper cleaning.
- Professional Cleaning: If you’re not comfortable cleaning the carburetor yourself, take it to a local repair shop.
Spark: The Ignition System
If you’ve ruled out fuel system issues, the next suspect is the ignition system, responsible for creating the spark that ignites the fuel-air mixture.
1. Spark Plug: The Heart of Ignition
The spark plug is the crucial component responsible for generating the spark.
Here’s how to inspect and replace the spark plug:
- Inspect for Wear: Remove the spark plug and inspect it for any signs of wear, such as cracked or fouled electrodes, excessive gap, or carbon buildup.
- Gap Adjustment: If the spark plug appears to be in good condition, use a spark plug gapping tool to adjust the gap according to the manufacturer’s specifications.
- Replacement: If the spark plug is worn or fouled, replace it with a new one of the correct type and heat range.
2. Spark Plug Wire: A Conductive Path
The spark plug wire delivers the electrical current from the ignition coil to the spark plug.
- Inspect for Damage: Check the spark plug wire for any cracks, frayed insulation, or loose connections.
- Replacement: If you find any damage, replace the wire with a new one.
3. Ignition Coil: Delivering the Power
The ignition coil converts low-voltage electricity from the battery into high-voltage electricity that powers the spark plug.
- Inspect for Cracks: Look for any cracks or damage to the ignition coil.
- Testing: If you suspect a faulty ignition coil, you can test it with a multimeter. If the ignition coil is not producing the correct voltage, replace it.
Compression: The Engine’s Strength
Compression refers to the pressure built up inside the engine cylinder during the compression stroke. Low compression can prevent the fuel-air mixture from igniting properly.
1. Compression Test: Measuring Engine Health
A compression test is a good way to assess the health of your engine’s compression.
- Compression Tester: Use a compression tester designed for small engines. Follow the instructions that come with the tester.
- Readings: A healthy engine should have compression readings within the range specified by the manufacturer.
- Causes of Low Compression: Low compression can be caused by worn piston rings, a damaged cylinder head, or a valve issue.
If your compression test results are significantly below the manufacturer’s specifications, you may need to take your lawn mower to a professional for further diagnosis and repair.
Troubleshooting Tips
- Battery Check: If your lawn mower has an electric starter, make sure the battery is charged. A weak battery can prevent the engine from cranking over.
- Choke Position: Make sure the choke is in the correct position. In some cases, engaging the choke can help to start the engine, especially when it’s cold.
- Air Filter: A dirty air filter can restrict airflow to the engine. Clean or replace the air filter if it’s dirty.
- Safety Switch: Check the safety switch that prevents the engine from starting unless the blade is disengaged. Ensure the switch is in the proper position.
- Run-on Fuel: If you’ve had your lawn mower sitting for a while, it might be helpful to use a product like “Start Your Engines,” which breaks down stale fuel in the system and makes it easier to start the engine.
Preventative Maintenance for a Long-Lasting Lawn Mower
Preventing problems is easier than fixing them. Here are some preventative maintenance tips for keeping your lawn mower running smoothly:
- Regular Maintenance: Follow the manufacturer’s recommended maintenance schedule for oil changes, air filter replacement, and spark plug replacement.
- Fuel Stability: Use fuel stabilizer in your gasoline, especially if you’re storing your lawn mower for extended periods.
- Winter Storage: Before storing your lawn mower for the winter, drain the fuel tank and carburetor. This will prevent fuel from going stale and causing problems in the spring.
- Cleanliness: Keep your lawn mower clean and free of debris. This will help to prevent clogs and other problems.
By following these tips, you can extend the life of your lawn mower and enjoy years of trouble-free mowing.
Frequently Asked Questions
1. Why is my lawn mower turning over but not starting?
This is a common issue that can be caused by a few different things. The most likely culprit is a lack of fuel. Make sure your gas tank is full and that the fuel lines are not clogged. You should also check the spark plug to see if it is clean and properly gapped. If the spark plug is dirty or worn out, it needs to be replaced.
If your mower still won’t start after checking these things, there could be a problem with the ignition system. This includes the ignition coil, spark plug wires, and the ignition switch. You can test the ignition system with a multimeter to see if there is a problem. If there is, you will need to replace the faulty part.
2. Why is my lawn mower turning over slowly?
A slow-turning mower engine is often caused by a weak battery. The battery may be old or discharged. You can test the battery with a voltmeter. If the voltage is below 12 volts, you need to charge or replace the battery.
Another common cause of slow turning is a problem with the starter motor. This can be caused by worn brushes, a faulty solenoid, or a bad starter motor. If the starter motor is faulty, it will need to be replaced.
3. Why is my lawn mower backfiring?
Backfiring is usually a sign of a problem with the carburetor. The carburetor may be dirty or the air-fuel mixture may be incorrect. You can clean the carburetor with carburetor cleaner and adjust the air-fuel mixture according to the manufacturer’s specifications.
Another possible cause of backfiring is a faulty ignition system. If the spark plug is fouled or the ignition coil is faulty, it can cause backfires. You should check the ignition system and replace any faulty parts.
4. Why is my lawn mower running rough?
A rough-running lawn mower can be caused by a variety of problems, including a dirty air filter, a clogged fuel filter, or a faulty spark plug. You should check these components and replace them if necessary.
You can also adjust the carburetor if the air-fuel mixture is incorrect. A clogged fuel line or a problem with the fuel pump can also cause a rough running engine. If you suspect a fuel-related issue, you should check these components and replace them if necessary.
5. Why is my lawn mower smoking?
Smoking from your lawn mower can be a sign of a number of problems. One of the most common causes is oil burning. This can be caused by worn piston rings or a faulty valve seal. If you see blue smoke, it’s likely that oil is being burned.
Another cause of smoking is water in the fuel. If you see white smoke, it’s likely that water is being burned. You should check your fuel tank for water and drain it if necessary.
6. Why is my lawn mower making a clicking noise?
A clicking noise from your lawn mower can be caused by a variety of problems. One common cause is a worn-out starter motor. The clicking noise may be the starter motor attempting to engage with the flywheel but failing to do so.
Another possibility is a faulty solenoid. The solenoid is responsible for providing the electrical current to the starter motor. If the solenoid is faulty, it will not be able to engage the starter motor.
7. Why is my lawn mower not starting after I change the spark plug?
If your lawn mower is not starting after you change the spark plug, there are a few things to check. First, make sure that you installed the new spark plug correctly. If you are unsure, consult your owner’s manual.
Next, check the spark plug gap. The spark plug gap needs to be set to the correct specification for your lawn mower. If the gap is too wide or too narrow, it will prevent the spark plug from firing correctly. Finally, check the spark plug wire to make sure that it is connected properly. If any of these components are faulty, they should be replaced.