It’s a frustrating experience, isn’t it? You pull the cord on your trusty lawn mower, it roars to life, but then sputters and dies just as you’re ready to tackle the overgrown grass. You check the fuel, the oil, even give it a good kick, but nothing seems to work. Why does your lawn mower start then stop? This article will guide you through the common culprits behind this infuriating problem and offer practical solutions to get your mower back in action.
Why Does My Lawn Mower Start Then Stop?
A lawn mower that starts then immediately stops can be caused by various issues related to fuel, spark, or air intake. Understanding these systems is crucial for troubleshooting and getting your mower back to its mowing glory.
Fuel System Issues
The fuel system plays a vital role in the mower’s ability to run. If the fuel isn’t getting to the engine properly or is of poor quality, your lawn mower may start then stop. Here are the most common fuel-related problems:
1. Old or Bad Gas
Gasoline can degrade over time, especially if it’s been sitting in the tank for a while. This degradation can lead to gum and varnish buildup in the fuel system, clogging the carburetor or fuel lines. Symptoms include the mower starting but running poorly or stopping after a short period.
Solution:
- Drain the old gas. Remove the fuel tank and drain the gasoline into a container. Properly dispose of the old gas.
- Replace with fresh fuel. Fill the tank with fresh, clean gasoline.
- Add fuel stabilizer. To prevent future problems, add fuel stabilizer to the gas. This helps prevent gum and varnish formation.
2. Clogged Fuel Filter
The fuel filter is a small but essential part of the fuel system. It traps dirt and debris that could clog the carburetor, preventing fuel flow. If the fuel filter is clogged, the mower may start but lack power or stop completely.
Solution:
- Replace the fuel filter. This is a simple and inexpensive fix. Check the owner’s manual for the location of the fuel filter.
3. Carburetor Problems
The carburetor is responsible for mixing air and fuel to create a combustible mixture. If the carburetor is dirty, clogged, or malfunctioning, it can cause the engine to start and then stop.
Solution:
- Clean the carburetor. This requires removing the carburetor from the engine and cleaning it thoroughly with carburetor cleaner.
- Rebuild the carburetor. If the carburetor is worn or damaged, you may need to rebuild or replace it.
Spark System Issues
The spark system is responsible for igniting the fuel-air mixture, making the engine run. If there’s a problem with the spark plug, spark plug wire, or ignition coil, the engine may start and then stop.
1. Fouled Spark Plug
A spark plug can become fouled with carbon deposits, oil, or fuel. This can prevent the spark plug from firing consistently, causing the engine to stop.
Solution:
- Clean or replace the spark plug. Remove the spark plug and inspect it for fouling. If it’s dirty, clean it with a wire brush or replace it with a new one.
2. Worn Spark Plug Wire
The spark plug wire carries electricity from the ignition coil to the spark plug. If the wire is damaged or worn, it may not deliver enough voltage to ignite the fuel-air mixture.
Solution:
- Inspect the spark plug wire. Check for any cracks, breaks, or corrosion. Replace the wire if necessary.
3. Faulty Ignition Coil
The ignition coil is responsible for generating the high voltage needed to fire the spark plug. If the coil is faulty, the engine won’t be able to ignite the fuel-air mixture.
Solution:
- Test the ignition coil. Use a multimeter to test the coil’s resistance. If it’s out of spec, replace the coil.
Air Intake Issues
The air intake system brings air into the engine, which is mixed with fuel to create the combustion process. If the air intake system is blocked or restricted, it can cause the engine to start and then stop.
1. Clogged Air Filter
The air filter is designed to trap dirt and debris from entering the engine. If the air filter is clogged, it can restrict airflow to the engine, causing it to stall.
Solution:
- Clean or replace the air filter. Remove the air filter and check its condition. If it’s dirty, clean it or replace it with a new one.
Other Possible Causes
While the above issues are the most common causes of a lawn mower starting and then stopping, other factors could be contributing to the problem. Here are some additional things to consider:
- Low Oil Level: Insufficient oil can cause engine damage. Check the oil level and add oil if necessary.
- Choke Problems: The choke helps enrich the fuel-air mixture for starting. If the choke is stuck or malfunctioning, the engine may start and then stop.
- Ignition Switch Issues: A faulty ignition switch can prevent the engine from receiving power.
- Fuel Tank Vent Issues: A clogged fuel tank vent can create a vacuum in the tank, preventing fuel from flowing to the engine.
Troubleshooting Tips
If your lawn mower starts and then stops, here are some troubleshooting tips to help you identify the problem:
- Inspect the fuel. Make sure the fuel is fresh, clean, and free of contaminants.
- Check the fuel filter. Ensure the fuel filter is not clogged.
- Inspect the air filter. Make sure the air filter is clean and not clogged.
- Test the spark plug. Check the spark plug for fouling and ensure it is firing properly.
- Check for loose connections. Inspect the wiring and connections for any loose or damaged components.
Final Thoughts
A lawn mower that starts and then stops can be frustrating, but with a little understanding of the engine systems and some basic troubleshooting, you can often diagnose and fix the problem yourself. Remember to always consult the owner’s manual for specific instructions and safety procedures. If you’re unable to solve the issue, it’s best to seek help from a qualified mechanic. By staying informed and tackling the problem head-on, you’ll be back to enjoying a perfectly manicured lawn in no time!
FAQs
Here are 7 frequently asked questions about why your lawnmower might be starting but then stopping:
1. Why Does My Lawn Mower Start Then Die Right Away?
If your lawnmower starts and then dies almost immediately, the problem is likely with the fuel system. This could be a clogged fuel filter, a faulty fuel pump, or a blockage in the fuel line. The fuel filter can become clogged with dirt and debris over time, preventing fuel from reaching the engine. The fuel pump may not be delivering enough fuel pressure, or there might be a leak in the fuel line. Check these components and replace them if necessary.
Additionally, a faulty spark plug or a dirty air filter could also be contributing to the problem. A spark plug that is worn or fouled will not ignite the fuel properly, while a dirty air filter can restrict airflow to the engine, making it difficult to start and run. Check the spark plug for wear and replace it if necessary. Clean or replace the air filter as well.
2. Why Does My Lawn Mower Start Then Stop After A Few Minutes?
If your lawnmower starts and runs for a short period before stopping, there could be a few potential issues. One possibility is that the carburetor is dirty or misadjusted. A dirty carburetor can cause fuel to flow unevenly, resulting in engine stalling. The carburetor might also need adjusting to ensure proper air-to-fuel ratio.
Another possibility is a problem with the ignition system, such as a faulty ignition coil or spark plug wire. The ignition coil provides the spark that ignites the fuel, and a malfunctioning coil can result in intermittent sparking, causing the engine to stop. Inspect the ignition coil and spark plug wire for any signs of damage or wear.
3. Why Does My Lawn Mower Start Then Stop When I Give It Gas?
If your lawnmower starts and then stops when you accelerate, the problem is likely related to the fuel system or the ignition system. A common culprit is a clogged or dirty carburetor. When you give the mower gas, the carburetor attempts to deliver more fuel, but the blockage prevents the necessary amount from reaching the engine, causing it to stall.
Another potential issue is a faulty ignition system. If the spark plug or ignition coil is not functioning properly, it may be unable to ignite the fuel effectively when the engine is under load. This can lead to the engine stopping when you try to accelerate.
4. Why Does My Lawn Mower Start Then Stop When It’s Hot?
If your lawnmower starts and runs fine when cold but then stops when it warms up, the problem could be related to overheating. This could be caused by a lack of coolant, a clogged radiator, or a faulty thermostat. Overheating can cause the engine to seize, leading to the mower stopping.
Another possibility is a problem with the ignition system, such as a faulty ignition coil or spark plug wire. When the engine is hot, the components can expand and malfunction, leading to intermittent sparking and engine stalling.
5. Why Does My Lawn Mower Start Then Stop When It’s Cold?
If your lawnmower starts and then stops when cold, the problem could be related to the fuel system. Cold weather can cause fuel to thicken, making it difficult for the engine to start and run. This can be especially true if the fuel is old or has been sitting for a long time.
Additionally, the carburetor might be misadjusted for cold weather conditions. The carburetor needs to adjust the air-to-fuel ratio depending on the temperature, and if it is not set correctly for cold weather, the engine may struggle to start and run.
6. Why Does My Lawn Mower Start Then Stop After I Change The Oil?
If your lawnmower starts and then stops after an oil change, the problem could be related to a few factors. The first is that the oil level may be too high. Overfilling the engine with oil can create pressure that hinders proper operation, leading to engine stalling.
Another potential issue is a faulty oil filter. If the oil filter is not seated correctly or if it is clogged, it can restrict oil flow, preventing the engine from running smoothly. Make sure the oil filter is properly installed and not blocked.
7. Why Does My Lawn Mower Start Then Stop And Smell Like Gas?
If your lawnmower starts and then stops and you smell gasoline, the problem is likely a fuel leak. This could be caused by a loose or damaged fuel line, a leaking fuel filter, or a faulty fuel pump.
Another possibility is a clogged carburetor. A clogged carburetor can cause fuel to overflow, resulting in a strong gasoline smell. If you smell gasoline, it is important to stop using the lawnmower immediately and investigate the source of the leak to prevent fire hazards.