The gentle hum of a lawnmower on a sunny Saturday morning can be a beautiful thing. But that idyllic scene can quickly turn into frustration when your mower sputters to a stop just as you’re getting started. This seemingly simple problem can have a surprising number of causes, from fuel issues to ignition trouble. This article will walk you through the most common culprits behind a lawn mower that starts then stops, providing you with the knowledge to diagnose and fix the problem yourself.
The short answer is that there are several reasons why your lawnmower might start and then stop. The most common reasons include:
- Fuel problems: A clogged fuel filter, bad gas, or a lack of fuel can all prevent your mower from running consistently.
- Ignition issues: A faulty spark plug, spark plug wire, or ignition coil can interrupt the spark needed to ignite the fuel.
- Air intake problems: A clogged air filter or a blocked air intake can starve the engine of the oxygen it needs to run.
- Engine problems: Issues with the carburetor, fuel pump, or other engine components can also prevent your mower from running smoothly.
Let’s take a closer look at each of these potential problems.
Fuel Problems
Fuel problems are among the most common reasons for a lawn mower starting and then stopping. Here are some of the most likely culprits:
Clogged Fuel Filter
The fuel filter is a small, but vital part of your lawn mower. Its job is to remove dirt and debris from the fuel before it reaches the engine. A clogged fuel filter can restrict fuel flow, causing your mower to start and then stop.
How to check the fuel filter:
- Locate the fuel filter: It’s usually a small, cylindrical object located near the fuel tank or the carburetor.
- Inspect the filter: Check for any visible dirt or debris. If the filter is visibly dirty, it’s likely clogged.
- Replace the filter: If the filter is clogged, replace it with a new one.
Bad Gas
Gasoline can degrade over time, especially if it’s not treated with fuel stabilizer. Old gas can gum up the carburetor and fuel system, preventing your mower from running properly.
How to check for bad gas:
- Smell the gas: Old gas often has a pungent, almost varnish-like smell.
- Check the date: If you’ve had the gas in your mower for more than 3 months, it’s probably time to replace it.
How to fix bad gas:
- Drain the fuel tank: Carefully drain the old gas from the tank and dispose of it properly.
- Replace with fresh gas: Fill the tank with fresh, stabilized gasoline.
Empty Fuel Tank
This might seem obvious, but a simple lack of fuel can lead to a lawnmower starting and then stopping.
How to check the fuel level:
- Locate the fuel tank: It’s usually located on the side or top of the mower.
- Check the level: Make sure the tank has enough fuel to run the mower for a reasonable period.
Ignition Issues
Ignition problems are another common culprit behind a lawn mower that starts and then stops. These issues relate to the spark that ignites the fuel in the engine.
Faulty Spark Plug
The spark plug is responsible for delivering the spark that ignites the fuel-air mixture in the combustion chamber. A faulty spark plug can cause misfires, leading to the mower starting and then stopping.
How to check the spark plug:
- Remove the spark plug: Use a spark plug wrench to carefully remove the spark plug from the engine.
- Inspect the plug: Look for signs of wear, damage, or fouling (black or oily deposits).
- Test the spark plug: If possible, test the spark plug with a spark plug tester.
How to fix a faulty spark plug:
- Replace the spark plug: Replace the old spark plug with a new one that’s the correct type for your mower.
Spark Plug Wire
The spark plug wire carries the electrical current from the ignition coil to the spark plug. A damaged or corroded wire can interrupt the flow of electricity, preventing the spark plug from firing.
How to check the spark plug wire:
- Inspect the wire: Look for any cracks, breaks, or signs of corrosion.
- Test the wire: If possible, test the wire with a continuity tester.
How to fix a faulty spark plug wire:
- Replace the wire: Replace the old wire with a new one that’s the correct type for your mower.
Ignition Coil
The ignition coil is responsible for generating the high-voltage electricity that powers the spark plug. A faulty ignition coil can prevent the spark plug from firing, causing the mower to start and then stop.
How to check the ignition coil:
- Inspect the coil: Look for any cracks, breaks, or signs of corrosion.
- Test the coil: If possible, test the coil with a multimeter.
How to fix a faulty ignition coil:
- Replace the coil: Replace the old coil with a new one that’s the correct type for your mower.
Air Intake Problems
Your lawnmower’s engine needs a steady supply of air to run properly. Problems with the air intake can restrict airflow, leading to the engine starting and then stopping.
Clogged Air Filter
The air filter prevents dirt and debris from entering the engine. A clogged air filter restricts airflow, making it difficult for the engine to run smoothly.
How to check the air filter:
- Locate the air filter: It’s typically located under a cover near the engine.
- Inspect the filter: Look for signs of dirt, dust, or debris. If the filter is visibly dirty, it’s likely clogged.
How to fix a clogged air filter:
- Replace the filter: Replace the old filter with a new one.
Blocked Air Intake
A blocked air intake can prevent air from reaching the engine. This can happen if the air intake is covered with debris or if there’s a blockage in the air intake tube.
How to check the air intake:
- Locate the air intake: It’s usually located near the carburetor.
- Inspect the intake: Check for any blockages or debris.
How to fix a blocked air intake:
- Remove any blockages: Carefully remove any debris or obstructions from the air intake.
Engine Problems
Sometimes, the issue with a lawn mower that starts and then stops lies within the engine itself. Here are some potential engine problems:
Carburetor Problems
The carburetor is responsible for mixing fuel and air to create the combustible mixture needed for the engine to run. A dirty or malfunctioning carburetor can cause problems with fuel flow, leading to starting and stopping issues.
How to check the carburetor:
- Inspect the carburetor: Look for any visible signs of dirt or debris.
- Clean the carburetor: If the carburetor is dirty, use a carburetor cleaner to clean it thoroughly.
How to fix carburetor problems:
- Rebuild the carburetor: If the carburetor is severely damaged or worn, it might need to be rebuilt or replaced.
Fuel Pump Problems
The fuel pump is responsible for delivering fuel from the tank to the carburetor. A faulty fuel pump can prevent fuel from reaching the carburetor, causing the mower to start and then stop.
How to check the fuel pump:
- Inspect the fuel pump: Look for any signs of damage or leaks.
- Test the fuel pump: If possible, test the fuel pump using a fuel pressure gauge.
How to fix a faulty fuel pump:
- Replace the fuel pump: Replace the old fuel pump with a new one that’s the correct type for your mower.
Troubleshooting Tips for a Lawn Mower That Starts Then Stops
Once you’ve identified some potential causes for your lawn mower’s starting and stopping problems, you can begin troubleshooting. Here are some general tips:
- Start with the simple things: Before diving into complex engine repairs, make sure to check the fuel level, air filter, and spark plug. These are the easiest things to check and often the culprits behind the problem.
- Listen for clues: Pay close attention to the sounds your mower makes when it’s running. A sputtering sound might indicate a fuel problem, while a clicking sound might suggest an ignition issue.
- Use a repair manual: If you’re not sure where to start, consult a repair manual for your specific model of lawn mower. This will provide detailed instructions and troubleshooting steps.
- Be patient and methodical: Troubleshooting can be frustrating, but it’s important to be patient and methodical. Take your time, check each potential problem carefully, and don’t rush to jump to conclusions.
Getting Professional Help
If you’ve tried all the troubleshooting steps and your lawn mower is still starting and then stopping, it might be time to seek professional help. A qualified mechanic can diagnose the problem and make the necessary repairs.
Preventative Maintenance
Regular maintenance is key to keeping your lawn mower running smoothly and preventing problems from arising. Here are some preventative maintenance tips:
- Change the oil regularly: Follow the manufacturer’s recommendations for oil changes.
- Clean the air filter: Check and clean the air filter regularly, as a dirty filter can restrict airflow and cause problems.
- Replace the spark plug: Replace the spark plug at least once a year, even if it appears to be working fine.
- Check the fuel system: Make sure the fuel lines and fuel tank are clean and free of debris.
- Store your mower properly: When storing your mower for extended periods, drain the fuel tank, clean the carburetor, and change the oil.
Conclusion
While a lawnmower that starts and then stops can be frustrating, it’s often a simple problem that can be solved with a little troubleshooting. By understanding the most common causes and following the steps outlined in this article, you can diagnose and fix the issue yourself and get back to enjoying your well-maintained lawn. Remember, preventative maintenance is key to avoiding these problems in the first place. With a little care and attention, your lawn mower will reward you with years of reliable service.
FAQ
Why does my lawnmower start then stop?
This is a common issue with lawnmowers, and there are a few reasons why it might be happening. The most common reason is that the engine is not getting enough fuel. This could be due to a clogged fuel filter, a problem with the fuel line, or a bad fuel pump. Another possibility is that the spark plug is fouled or damaged. A fouled spark plug will prevent the engine from igniting the fuel, while a damaged spark plug will not be able to produce a spark at all.
Finally, the problem could be with the carburetor. The carburetor is responsible for mixing air and fuel in the correct proportions. If the carburetor is dirty or damaged, it will not be able to do this properly, which will cause the engine to start then stop.
How do I troubleshoot my lawnmower that starts then stops?
There are a few things you can do to troubleshoot your lawnmower. First, check the fuel tank to make sure that it is full and that the fuel is fresh. If the fuel is old or contaminated, it may not be able to ignite properly. Next, check the fuel filter to make sure it is not clogged. If it is, replace it. You should also check the fuel line to make sure it is not kinked or damaged.
Finally, check the spark plug. If the spark plug is fouled, you can clean it with a wire brush or replace it. If the spark plug is damaged, you will need to replace it. If you have checked all of these things and the lawnmower still starts then stops, you may need to take it to a qualified mechanic to be diagnosed and repaired.
What are some signs of a bad spark plug?
A bad spark plug can cause a variety of problems with your lawnmower, including starting and stopping issues. Here are some signs that your spark plug may be bad:
- Your lawnmower starts then stops.
- Your lawnmower is difficult to start.
- Your lawnmower runs poorly or misfires.
- Your lawnmower has a black or sooty exhaust.
If you are experiencing any of these problems, it is a good idea to check your spark plug.
How do I clean a spark plug?
Cleaning a spark plug is a simple process that can help to improve the performance of your lawnmower. Here are the steps on how to clean a spark plug:
- Disconnect the spark plug wire from the spark plug.
- Use a spark plug wrench to remove the spark plug from the engine.
- Inspect the spark plug for any signs of damage or wear.
- Use a wire brush to clean the electrodes of the spark plug.
- If the spark plug is still dirty or damaged, replace it with a new one.
- Reinstall the spark plug and tighten it to the correct torque.
- Reconnect the spark plug wire to the spark plug.
What is the difference between a fouled spark plug and a bad spark plug?
A fouled spark plug is one that has become covered in carbon deposits from the combustion process. This buildup of carbon can prevent the spark plug from firing properly. A bad spark plug is one that is damaged or worn out and can no longer produce a spark. You can tell the difference between a fouled and bad spark plug by inspecting the electrodes. A fouled spark plug will have a black or brown deposit on the electrodes, while a bad spark plug will have a gap that is too large or too small.
What are some common problems with the carburetor on a lawnmower?
The carburetor is a critical component of your lawnmower’s engine and is responsible for mixing air and fuel in the correct proportions for combustion. However, it can be prone to problems, especially if it’s dirty or damaged. Here are some common carburetor problems that can cause your lawnmower to start then stop:
- Clogged jets: The jets in the carburetor are small openings that allow fuel to flow into the engine. They can become clogged with dirt and debris, restricting the flow of fuel.
- Damaged float: The float in the carburetor is responsible for controlling the level of fuel in the bowl. If the float is damaged, it can cause the engine to run too rich or too lean.
- Dirty carburetor: The carburetor can become dirty over time, especially if it’s not properly maintained. A dirty carburetor can cause the engine to run poorly or even stall.
How do I know if my lawnmower needs a new carburetor?
If you’ve checked all of the other possible causes for your lawnmower starting then stopping, and you still haven’t found the problem, then it’s possible that the carburetor is faulty. Here are a few signs that your lawnmower needs a new carburetor:
- The lawnmower won’t start.
- The lawnmower starts but then dies immediately.
- The lawnmower runs poorly, sputters, or backfires.
- The lawnmower has a black or sooty exhaust.
- The lawnmower idles too high or too low.
- The lawnmower consumes too much fuel.
If you’re experiencing any of these problems, it’s best to take your lawnmower to a qualified mechanic to have the carburetor inspected and repaired or replaced.