The sweet, warm scent of freshly cut grass. The satisfying hum of a well-tuned engine. The feeling of accomplishment after tackling your lawn. But what happens when that idyllic scenario is disrupted by a frustratingly common problem: your lawn mower starts, then immediately dies? This article will delve into the common culprits behind this annoying issue, providing you with the knowledge to diagnose and potentially fix it yourself, saving you time, money, and a whole lot of frustration.
In essence, the reason your lawn mower starts then stops often boils down to issues with fuel delivery, spark, or a faulty carburetor. Let’s explore each of these potential problems in detail, along with practical troubleshooting tips.
Fuel Delivery Issues: The Heart of the Problem
The engine of your lawn mower requires a consistent flow of fuel to keep running. When the fuel delivery system malfunctions, you might experience starting problems or a sudden shut-off. Here’s a breakdown of the most common fuel delivery issues:
1. Empty Fuel Tank: The Obvious Culprit
The simplest explanation for a lawn mower that starts and stops is a lack of fuel. Always check your fuel tank level before starting your mower.
2. Old or Bad Gas: The Hidden Enemy
Gasoline, unlike wine, does not improve with age. Over time, gasoline loses its volatility, making it difficult to ignite and causing engine problems.
Signs of Bad Gas:
- Stale Smell: Fresh gas has a clean, almost sweet odor. Old gas smells pungent and stale.
- Sediment: A brown, gummy residue forms at the bottom of the fuel tank as gas deteriorates.
Solution:
- Empty and Replace: If you suspect your gas is old, the best solution is to completely drain the fuel tank and replace it with fresh, high-octane gasoline.
- Fuel Stabilizer: For longer storage, consider adding a fuel stabilizer to your gasoline to prevent deterioration.
3. Clogged Fuel Lines and Filters: The Silent Obstruction
Over time, debris and sediment can build up in your lawn mower’s fuel lines and filter, hindering the flow of fuel to the carburetor.
Signs of Clogged Fuel Lines/Filter:
- Weak Engine Performance: The engine may sputter or hesitate, indicating a restricted fuel supply.
- Difficult Starting: It might take longer than usual for the mower to start, or it might start and then die immediately.
Solution:
- Clean or Replace: The fuel filter is usually a small, replaceable component. The fuel lines can be cleaned or replaced if necessary. Consult your owner’s manual for specific instructions.
Spark Ignition: The Firestarter
A properly functioning spark plug is essential for igniting the fuel-air mixture in your lawn mower’s engine. If the spark is weak or absent, your lawn mower will struggle to start or run.
1. Fouled Spark Plug: The Spark Killer
A fouled spark plug is one that is coated in carbon, oil, or other deposits, preventing it from producing a strong spark.
Signs of a Fouled Spark Plug:
- Difficult Starting: The engine may crank but not fire.
- Black Smoke: Excessive black smoke coming from the exhaust indicates a rich fuel mixture, often due to a fouled spark plug.
Solution:
- Clean or Replace: Remove the spark plug, clean it with a wire brush, or replace it with a new one.
2. Worn Spark Plug Wires: The Broken Connection
The spark plug wires, which connect the spark plug to the ignition system, can become worn, cracked, or damaged over time, causing a weak or interrupted spark.
Signs of Worn Spark Plug Wires:
- Intermittent Starting Problems: The mower might start then stop, or it might start but run poorly.
- Visible Damage: Inspect the spark plug wires for any cracks, breaks, or fraying.
Solution:
- Replace: If the spark plug wires are damaged, replace them with new ones.
Carburetor Issues: The Fuel and Air Mixer
The carburetor is responsible for mixing fuel and air in the correct proportions for combustion. A faulty carburetor can cause a variety of problems, including starting issues and engine stalling.
1. Dirty Carburetor: The Choked System
Over time, dirt, debris, and gum deposits can accumulate in the carburetor, interfering with the fuel and air mixture.
Signs of a Dirty Carburetor:
- Difficult Starting: The engine may take longer than usual to start, or it might start and then die immediately.
- Engine Stalling: The mower may run for a short time and then stall unexpectedly.
- Black Smoke: Excessive black smoke coming from the exhaust indicates a rich fuel mixture, often due to a dirty carburetor.
Solution:
- Clean or Replace: The carburetor can be cleaned by disassembling it and soaking it in carburetor cleaner. If the carburetor is severely damaged, it may need to be replaced.
2. Fuel Line to Carburetor: The Broken Link
The fuel line that connects the fuel tank to the carburetor can become cracked, kinked, or clogged, interrupting the flow of fuel.
Signs of a Problem with the Fuel Line to the Carburetor:
- Engine Stalling: The mower may run for a short time and then stall unexpectedly.
- Visible Damage: Inspect the fuel line for any cracks, kinks, or signs of leaking.
Solution:
- Replace: If the fuel line is damaged, replace it with a new one.
Troubleshooting Steps: Finding the Root Cause
Now that you have a better understanding of the potential causes of your lawn mower starting and stopping, it’s time to tackle the troubleshooting process:
- Inspect the Fuel Tank: Ensure the fuel tank is not empty and the gas is fresh. Consider using a fuel stabilizer if you store your mower for extended periods.
- Check the Spark Plug: Remove the spark plug, inspect it for fouling, and clean it with a wire brush or replace it if necessary.
- Inspect the Spark Plug Wires: Look for any cracks, breaks, or fraying. Replace the wires if they are damaged.
- Examine the Fuel Lines: Inspect the fuel lines for any cracks, kinks, or signs of leaking. Replace any damaged fuel lines.
- Clean the Carburetor: If the carburetor is dirty, clean it thoroughly with carburetor cleaner. If necessary, replace the carburetor.
Seeking Professional Help: When to Call a Mechanic
While many lawn mower problems can be solved with basic troubleshooting, some issues require the expertise of a qualified mechanic. Here are some signs you should call a professional:
- Engine Damage: If you hear knocking or grinding noises coming from the engine, or if the engine is smoking excessively, it could indicate internal damage.
- Fuel System Leaks: If you notice significant fuel leaks, it’s best to have a mechanic inspect the system for potential safety hazards.
- Complex Electrical Problems: If you’re unfamiliar with electrical systems, leave any electrical repairs to a professional.
Conclusion: A Well-Maintained Lawn Mower is a Happy Lawn Mower
By understanding the common causes of a lawn mower starting then stopping and following the troubleshooting steps outlined above, you can hopefully diagnose and resolve the issue yourself. Regular maintenance, such as changing the spark plug, cleaning the carburetor, and using fresh fuel, will go a long way in preventing these problems and ensuring a smooth, reliable mowing experience. Remember, a happy lawn mower means a happy lawn!
Frequently Asked Questions
1. Why Does My Lawn Mower Start Then Stop Right Away?
This is often a sign of an issue with the fuel system. The engine might be receiving a burst of fuel initially, but then the flow stops. There could be a blockage in the fuel line, a problem with the fuel filter, or even a faulty fuel pump. Inspect the fuel lines for any kinks or blockages, and check the fuel filter to ensure it’s clean. If you suspect the fuel pump is at fault, it’s best to have it inspected by a professional.
2. Why Does My Lawn Mower Start Then Stop After Running For a Short Time?
This scenario points towards a potential issue with the carburetor. The carburetor is responsible for mixing fuel and air for the engine. If it’s dirty or malfunctioning, it might not be supplying the correct mixture, leading to the engine stalling. A common solution is cleaning the carburetor with carburetor cleaner. If cleaning doesn’t resolve the issue, it might be time for a new carburetor.
3. Why Does My Lawn Mower Start Then Stop When I’m Mowing?
This could be a sign of a faulty ignition system. The ignition system is crucial for igniting the fuel-air mixture. The problem might lie with the spark plug, spark plug wires, or the ignition coil. Check the spark plug for signs of wear or fouling. Also, inspect the spark plug wires for cracks or damage. If the problem persists, the ignition coil might require replacement.
4. Why Does My Lawn Mower Start Then Stop When It’s Hot?
This issue could be caused by overheating. When the engine gets hot, the fuel can vaporize, leading to a lean fuel-air mixture. This can cause the engine to sputter and stall. Make sure the cooling fins are clean and free of debris. If the engine is still overheating, the cooling system might need attention.
5. Why Does My Lawn Mower Start Then Stop When I Release the Throttle?
This is a common problem with lawn mowers that have a governor. The governor regulates the engine speed, and if it’s malfunctioning, it can cause the engine to stall when the throttle is released. Inspect the governor linkage for any damage or wear. Also, ensure the governor arm is moving freely.
6. Why Does My Lawn Mower Start Then Stop When It’s Cold?
The issue might lie with the choke. The choke helps enrich the fuel-air mixture when the engine is cold. If the choke is not functioning correctly, it might not be providing enough fuel to start and run the engine properly. Check the choke cable to make sure it’s operating smoothly and the choke plate is closing properly.
7. Why Does My Lawn Mower Start Then Stop When I’m Using a Mulching Blade?
A mulching blade increases the workload of the engine, potentially causing it to overheat and stall. If you recently switched to a mulching blade, make sure the engine is capable of handling the increased load. You might also want to adjust the mowing height to reduce the strain on the engine.