Lawnmower Stops Running When Hot, Causes and Fixes

Are you frustrated by a tool that fails when you need it most? Our expertise will help you understand why and how to fix this, quickly getting you back to work. We provide efficient solutions to ensure your productivity.

A lawnmower stopping when hot often stems from overheating due to clogged cooling fins or air intake. Also, check spark plugs, air filters, and carburetors. Clean cooling fins and replace air filters regularly. Proper maintenance prevents overheating.

Say goodbye to overheating issues with your lawnmower. Dive into our comprehensive guide to understand why your lawnmower stops when hot and how to fix it. Keep reading for a smooth, hassle-free mowing experience! Enjoy your gardening!

Reason 1: Lawnmower Engine Overheating

Generally, all mechanical processes result in the production of heat as a by-product because of friction. An enormous amount of heat is produced in a lawnmower engine due to the combustion of compressed gas in the cylinder. This chamber will get damaged if not properly maintained.

Additionally, heat is generated due to friction between moving parts. For this reason, the lawnmower engine gets heated to very high temperatures only minutes after starting. This temperature keeps increasing during the mower’s operation in an overheating engine until it is too hot to work correctly.

• Clogging Issues Leading to Overheating

It stops working and will not start again until it cools down. The engine can get clogged with other debris, leading to a broken cooling system. Using a coolant is a great way to manage the engine’s temperature.

Adding more coolant regularly and changing it when necessary is also essential. A lawnmower engine also needs a lubricant to reduce friction and heat production. You can go to Amazon for various options to purchase a new coolant or lubricant.

● Cooling Fins:

Most of the heat dissipated by the engines gets scattered to the surrounding air by the heat transfer mode of “convection.” Heat transfer to the environment by convection is directly proportional to the hot surface area (the engine block in this case).

If the desirable surface area is increased, heat dissipation will increase, and heating will be avoided. This increase in the region is achieved by using fins so that loss of compression is minimized. To prevent an engine from overheating, fins are molded on the exterior surface of the engine block.

– What Happens When Grass Clippings Stick to the Fins

When a lawnmower is used, grass clippings, dirt, and debris stick to the fins. If the fins are not cleaned regularly, a thick layer of debris will accumulate on them. This layer will act as a blanket, reducing heat transfer from the fins to the environment, resulting in the engine’s overheating.

One of the reasons behind this is that plugs will get dirty, and more oil will be needed. Therefore, you need to clean the chamber regularly to ensure that compression is maintained.

● Fix Lawnmower Engine Overheating

If your mower stops running after some minutes of operation, let it cool down and then check the fins. If they are covered with debris, clean them with a brush until their entire surface is exposed. If dirty fins were the cause of the problem, your mower wouldn’t stop running again.

Reason 2: Air Filter and Muffler

Your lawnmower engine takes in the cool, fresh air in each cycle and expels hot exhaust gases produced by combustion. An interruption in the inflow of cool air and the hot exhaust gases’ outflow can cause the engine to overheat and eventually stall.

The incoming cool air passes through the air filter before reaching the engine. Dirt particles in the air can clog the air filter. Lawnmower air filters usually get dirty pretty quickly and must be cleaned regularly.

The hot exhaust gases are removed from the engine through the muffler. If the muffler is dirty, exhaust gas’s outflow rate will decrease, increasing the engine temperature. Over time, the engine will get overheated and stall.

● Fix the Air Filter and Muffler

If you are faced with your mower stopping when hot, check the air filter and the muffler. Clean them if they are dirty. Both of these can be cleaned with water and a brush. Make it a habit to clean the two components regularly. Replace them if they are too dirty to be cleaned.

Reason 3: Dirty Carburetor

The carburetor’s job is to mix air and fuel in the correct balance and provide the mixture for combustion in the cylinder. A faulty carburetor will fail to prepare the right mix, leading to improper or incomplete combustion in the cylinder.

Improper combustion means sufficient power will not be produced in the engine, causing the mower to stop running. Lawnmower carburetors get dirty and clogged because of the sticky gum-like material produced if gas sits in the tank too long.

A carburetor’s internal mechanism comprises needle valves, spray jets, springs, and floats. The buildup of the sticky gum-like material can clog these components, hampering their smooth operation.

● How to fix Dirty Carburetor

You can clean the carburetor yourself with help from online tutorials. Repairing a malfunctioning carburetor is not that simple and is better left to the technicians. If the carburetor is faulty, replace it with a new one.

Reason 4: Vapor Lock

Vapor lock is when hot gases get trapped in the fuel tank and can cause the engine to stall. In most lawnmowers, the fuel tank caps have small holes that allow hot gases to escape from the fuel tank. If a fuel tank cap is dirty, these vent holes get filled, blocking the outflow of hot gases.

When this happens, the pressure inside the fuel tank rises, causing the heated gases to flow in reverse and move out of the carburetor, immediately shutting the engine.

● Fix Vapor Lock

If your lawnmower’s fuel tank cap is dirty, clean it or replace it with a new one. Open vent holes will ensure reduced pressure in the fuel tank, preventing the vapor lock condition.

Reason 5: Gas and Oil Problems

Gas sitting in the tank of a stored mower will go bad after some days because of oxidation and evaporation. Gas in the tank produces sticky material that clogs the fuel lines and the carburetor.

We have already discussed the adverse effects of a clogged carburetor. Before you start a mower that has been stored, make sure that its gas tank is empty and fill it with fresh gas.

You might also have to clean the fuel lines if old gas was in your mower. In general, check the gas before starting your mower to see if the gas level is enough for the mower to keep running. If the gas level is too low, the mower will start all right but stop running some minutes later.

● Fix Gas and Oil Problems

The engine will overheat and stall if the oil level is too low. So, ensure enough oil in the crankcase before starting the mower. Using the correct oil and changing the oil regularly is also crucial. We recommend you change the oil after every 25 hours of operation.

Reason 6: Moisture in Fuel Lines

Water in the fuel lines or the gas tank can also cause your lawnmower to stop running. This is because moisture does not mix with gasoline and causes problems with the ignition if it enters the engine.

● Fix Moisture in Fuel Lines

Water can contaminate the fuel either because of condensation in the fuel tank and fuel line or moisture entry into the fuel line because of a loose gas cap.

If water has contaminated the fuel, the only remedy is to drain the fuel and put fresh gasoline in your lawnmower. It would be even better to clean the fuel tank before putting in new petrol.

Reason 7: Faulty Spark Plugs

A lawnmower with a faulty spark plug will either not start or stop running some minutes after starting. Spark plug faults include dirty and corroded electrodes, broken porcelain housing, and carbon buildup at the firing end.

● Fix Faulty Spark Plugs

You can clean dirty spark plugs. You can use sandpaper or a file to remove the carbon buildup, but a broken spark plug needs to be replaced.

When replacing a spark plug, ensure that the new spark plug matches the old one in the plug gap. Spark plugs are not expensive, and you can easily find one at part shops.

Reason 8: Loose Bolts

After prolonged use, the bolts that hold various engine components together can become loose. Loose bolts create tiny spaces that can enlarge because of metal expansion as the engine heats up. Through these gaps, the engine can draw in excess air. This messes the air-fuel ratio and causes the engine to stall.

● Fix Loose Bolts

We recommend you check the bolts connecting the intake manifold to the engine block and the bolts regularly holding the carburetor in place. Tighten these bolts whenever they become loose.

Remarks:

Malfunctioning engine parts, problems with gas and oil, insufficient cooling, etc., can cause the engine to stop some minutes after starting. If you are unfamiliar with the causes behind a stalling engine, you might get worried and rush to a technician’s shop.

However, with basic info on this topic, you can diagnose your mower and fix this problem yourself. As you can see from our information in this blog post, most of these problems are not too serious, and their fixes are not too difficult. So, stop worrying, let the engine cool, then start working. 

Causes of Overheating in Lawnmowers

An overheating lawnmower might be due to a variety of factors. Among these are air leaks and worn-out pistons. Air leaks allow air to seep into undesired places, reducing the engine’s functionality, while worn-out pistons reduce the engine’s compression efficiency.

• Troubleshooting Lawnmower Overheating

In diagnosing the cause of an overheating lawnmower, it is best to approach it systematically, eliminating one potential cause at a time. Always perform the most straightforward checks first before proceeding to the complex ones.

• Clogged Air Filter

A common culprit for overheating is a clogged air filter. They restrict airflow and force the lawnmower to work hotter and more complexly.

Taking the time to clean or replace your air filter can save your machine from unnecessary damage. A clean air filter allows the engine to breathe freely, reducing the chance of overheating.

• Dirty Fuel Filter

A dirty fuel filter plays a similar role. It restricts fuel flow, causing the engine to run lean and potentially stop running. It is essential to clean the fuel filter regularly or replace it when necessary. Ensuring a clean fuel supply enables your lawnmower engine to run smoothly and at the correct temperature.

• Faulty Spark Plug

The spark plug, particularly with a wider electrode gap, can also be a reason behind overheating. The wide gap prevents the spark plug from firing consistently, causing the engine to labor and produce more heat. Replacing the faulty spark plug would be best to resolve this issue. Spark Plug Basics (ou.edu).

• Debris and Low Oil Levels

Debris in the cooling fins and low oil levels are often overlooked causes of overheating. Keeping the cooling fins clean and adding oil whenever necessary is essential. These minor maintenance tasks collectively prevent a temperature rise in the engine.

• Poor Lubrication

Poor lubrication due to low oil levels can also cause overheating. It may even stop the lawnmower from running entirely. I cannot stress enough the importance of checking oil levels regularly and adding oil when required. Adequate oil levels ensure smooth operation and prevent overheating.

• Deteriorating Compression

A lawnmower’s engine can stop running due to poor compression, another contributor to overheating. This is often a result of worn-out parts and loose bolts. In such a case, replacing the worn parts and tightening the bolts is the way to go.

• Faulty Fuel Lines

Collapsed, cracked, or clogged fuel lines are also potential causes. All these conditions restrict fuel movement, causing the engine to work harder, thus generating excess heat. Using a fuel cleaner or replacing the fuel lines may be required.

• Regular Maintenance is Key

Preventing overheating issues involves regular maintenance of your lawnmower. Cleaning or replacing the air and fuel filters, monitoring oil levels, and overall machine inspection help maintain efficiency and prevent overheating.

Regular maintenance might hold the key to the longevity of your lawnmower. Remember, investing little time in preventative maintenance can save you the cost and trouble of repairing an overheated engine.

• Issue 1: Engine Overheating

The main reason why lawnmowers may stop working when hot is engine overheating. This often occurs when the engine’s fins get covered in debris. These fins are designed to dissipate heat, ensuring the machine runs smoothly and efficiently.

If these are blocked by debris, they cannot perform this function, leading to engine shutdown. Regular cleaning of engine fins can help to mitigate this issue.

• Problem 2: Dirty Air Filter and Muffler

A dirty air filter and muffler are other common problems that can cause a lawnmower’s engine to stop when hot. They are designed to allow unrestricted airflow and exhaust gas flow, respectively; when they are clogged, the airflow gets restricted.

This results in the engine becoming stressed, thus triggering the protective shutdown mechanism. Regular maintenance, including cleaning the air filter and muffler, can prevent this.

• Issue 3: Dirty Carburetor

A dirty carburetor is another factor that may lead to the lawnmower stopping when hot. Carburetors are responsible for mixing air and fuel in the right proportions for combustion.

When the carburetor is dirty, it hinders the proper mixture of fuel and air, resulting in inefficient burning and, in some cases, engine shutdown. Cleaning the carburetor regularly can prevent this problem.

• Problem 4: Vapor Lock

Vapor lock is a condition that can also cause the lawnmower to stop. This occurs when heated gases get trapped in the fuel tank, disrupting the fuel’s flow to the engine.

The trapped vapors create a lock, preventing the fuel from reaching the engine and resulting in engine shutdown. Vapor locks are more common in older machines and hot weather.

• Issue 5: Gas and Oil Problems

Old gas and engine oil can contribute significantly to the lawnmower’s engine shutting down. Gasoline, especially when stored improperly, can develop sediments that can clog the fuel lines or carburetor, disrupting the fuel’s flow.

On the other hand, old engine oil can lose its lubricating properties, causing friction and overheating. Regularly changing the gas and engine oil based on the manufacturer’s instructions can prevent these issues.

• Problem 6: Moisture in Fuel Lines

Moisture in fuel lines does not mix well with gasoline, disrupting the ignition process. When this happens, the lawnmower can stop running when hot, as the engine cannot produce enough energy needed for operation. A fuel stabilizer or gas-line antifreeze can help keep moisture from fuel lines.

• Issue 7: Spark Plug Issues

A faulty spark plug, specifically dirty electrodes or carbon buildup, can hamper ignition. If there’s no adequate spark to ignite the fuel-air mix in the cylinders, the engine will not run. Regular inspection and replacement of spark plugs can resolve this problem.

• Problem 8: Loose Bolts

Loose bolts on engine components can create gaps, allowing excess air into the engine, which disrupts the fuel-air mix and can cause stalling. Regular inspection and tightening of these bolts can prevent a loose bolt from causing your lawnmower to stop running.

For more detailed information about lawnmower maintenance and troubleshooting, check this link to the website of the Royal Horticultural Society, a reliable non-profit organization dedicated to all forms of gardening.

– Reason 9: Plugged Mower Deck

A plugged mower deck is high on the list of common issues. This usually happens when grass clippings and debris bits clog your mower’s inner workings.

Regular cleaning is my recommended way to combat this issue. Remember to turn off and safely secure your machine before cleaning. Here is a link to a .edu site with more tips on mowing and maintenance.

– Reason 10: Incorrect Engine Oil Type

Using the incorrect engine oil type in your mower can lead to severe complications. Always check your specific model’s manual to ensure you’re utilizing the correct oil, or you could inadvertently cause severe engine damage.

– Reason 11: Low Coolant Level

A low coolant level may lead to engine overheating, resulting in poor performance and potential damage. Ensure your mower’s coolant levels are regularly checked and refilled. This simple habit can greatly help extend your machine’s life and performance.

– Reason 12: Faulty Ignition Switch

A faulty ignition switch is also a common issue behind lawnmower problems. If the mower isn’t starting despite all other components being in good shape, there’s a good chance it’s the ignition switch. Consult a professional for repairs or replacements.

– Reason 13: Clogged Fuel Filter

If the fuel filter is clogged, the fuel can’t travel from the tank to the engine, leading to starting issues. Regularly check the condition of the fuel filter, replacing it when necessary.

– Reason 14: Faulty Fuel Pump

Like the clogged fuel filter, a faulty fuel pump can disrupt fuel flow, leading to inadequate performance or inability to start. The fuel pump needs to function effectively for optimum mower performance.

– Reason 15: Faulty Safety Switch

A defective safety switch may cause your lawnmower not to start or run correctly. The safety switch ensures the engine shuts down during specific unsafe conditions. Hence, a malfunction of this switch can disrupt regular operation.

– Reason 16: Electrical Wiring Issues

Electrical wiring issues might induce several mower problems. Regularly inspect the wiring. Any signs of fraying, cuts, or loose connections should be addressed immediately.

– Reason 17: Worn-Out Drive Belt

A worn-out drive belt may result in irregular or slow movement of the mower. Over time, the drive belt can wear and stretch, reducing its efficiency. Check and replace it as needed to ensure smooth operation.

– Reason 18: Dirty Fuel Tank

A dirty fuel tank can also cause operational issues. Dirt and debris in the tank can obstruct fuel delivery to the engine. Regular cleaning of the fuel tank can help avoid this issue.

– Reason 19: Low Battery Voltage

Low battery voltage may cause starting problems or lead to a complete mower shutdown. Test the battery periodically, especially if the mower is not working correctly.

– Reason 20: Faulty Governor

The governor plays a crucial role in controlling the speed of the mower. A faulty governor may produce erratic speeds or stall the engine. It’s best to consult a certified professional to diagnose and fix this issue.

Reasons for Lawn Mower Startup and Running Problems

• Reason 1: Defective Coil

The ignition coil in your lawn mower is a critical component of the ignition system, generating the high voltage needed for the spark plug to ignite the gasoline. When this coil becomes defective, its ability to produce this voltage can be impeded, resulting in difficulties starting and running the mower.

Checking the coil with a multimeter is recommended to verify its functionality. Information on ignition coils and how they work can be found on the University of Colorado Boulder’s .edu website.

• Reason 2: Vacuum Created by the Gas Cap Vent

The gas cap vent is another critical area to inspect in case of a startup problem. This vent allows air to enter the fuel tank as gas is used, maintaining atmospheric pressure inside the tank. If the vent is blocked, a vacuum can form within the tank, which prevents fuel from flowing properly.

When this happens, the mower may only run for a few minutes before stalling. Checking the vent for debris or damage can resolve this issue.

• Reason 3: Spark Issues

The spark that ignites the gasoline is crucial for lawn mower operations. Issues concerning the spark plug, including deposits, wear, or improper gap spacing, can cause startup and running problems.

Keeping the spark plug clean, replacing it when necessary, and ensuring the correct gap setting can increase the performance and longevity of your mower.

• Reason 4: Automatic Choke Sticking Closed

A stuck choke on a lawn mower can also make starting or running difficult. The choke aims to restrict airflow to increase the fuel-air mixture at startup, aiding the cold engine to warm up.

If the automatic choke sticks in the closed position, it can cause a fuel mixture that is too rich, leading to problems such as flooding and even preventing the engine from starting. Regular inspection and proper machine maintenance can help avoid such choke issues.

• Reason 5: Clogged Air Cleaner

The air cleaners role cannot be underestimated. It ensures that the air entering the carburetor is clean and free from contaminants.

However, when the air cleaner is clogged, it may limit the air available for the fuel mixture, affecting the engine’s performance. Regular cleaning or replacing the air filter as necessary is strongly recommended.

• Potential Dangers of Heat Stroke

Operating your lawn mower during extreme heat can pose certain health risks, including heat stroke. Heat stroke is a condition caused by your body overheating and can be severe and potentially dangerous.

It is recommended to mow early or late in the evening during hot weather to ensure you stay hydrated and take regular breaks.

• Common Difficulties Encountered When Starting or Running a Mower

Several factors may cause difficulties in starting or running your lawn mower properly. These include malfunctioning components such as the spark plug, fuel shut-off valve, air filter, throttle cable, choke cable, and carburetor.

All these parts should be routinely checked and maintained to ensure the mower’s optimal performance. Ignition problems can also be traced to an issue with the ignition coil. More detailed information on ignition systems can be found at the DMV .gov website.

– How Debris Can Hinder Blade Movement

Accumulation of grass clippings in the mower’s deck can also cause problems. This unattended debris can hinder blade movement, overload the engine, and pose a potential fire hazard.

Therefore, regular deck cleaning is integral to maintaining a healthy and efficient mower. The Cornell University’s .edu website offers a simple guide for cleaning your mower deck.

In conclusion, remember that regular inspection, cleaning, and, where needed, parts replacement can eliminate most issues with your lawn mower. It’s important to remember that maintaining your machine isn’t just about ensuring it runs well. It’s also about safeguarding your health while using it.

Essential Lawn Mower Maintenance Tips

• Regular Maintenance for Optimal Performance

Consistent maintenance and cleaning are paramount to prevent performance issues in your lawn mower. From my experience, regular upkeep extends the machine’s lifetime and ensures it operates smoothly. Patchy lawn cutting is often a sign of a poorly maintained mower.

• Dealing with Cooling Fin Issues

When your lawn mower overheats and stalls more frequently, the culprit is likely clogged cooling fins. Cooling fins regulate the engine’s temperature, so when they’re blocked, overheating ensues. Therefore, ensure you regularly clean the cooling fins to prevent clogging.

• Ignition Coil Problems

I recommend using a multimeter or an ignition coil tester to identify if your ignition coil is problematic. These handy tools help detect any faults that may hinder the optimal functioning of your mower.

The Pennsylvania State University provides a comprehensive guide on how to use multimeters effectively (source).

• The Need for Thorough Carburetor Cleaning

Over time, your carburetor may experience clogs, resulting in performance issues. Employ a carburetor cleaning kit and spray to counter this. It’s an effective remedy that has worked in my case repeatedly.

• Recognizing and Managing Valve Problems

Valve problems in a lawn mower usually crop up due to an overheated engine or a broken valve. The functionality of your engine is highly dependent on its valves, so ensure they remain in good condition.

• Proper Fueling

To avoid fuel-related issues, using the correct gas type is essential. For the best maintenance, consider replacing the gas every 30 days – a small step that significantly changes your machine’s performance.

• Regular Checks on Screws and Bolts

Engine breakdown or other issues can often be resolved by something as simple as checking and tightening screws and bolts regularly.

Minor discrepancies are easily overlooked but can lead to significant problems over time. Regular inspections and consequent adjustments can circumvent many such hassles.

• Importance of Air Filter Replacement

Air filters play a crucial role in your mower’s operation. Over time, they tend to become dirty and less effective. To maintain a smooth running mower, replace your air filters after every 25 hours of use.

• Dealing with a Dirty Mower Deck

Excessive clogging and overheating are often symptoms of a dirty mower deck. It is advisable to clean the mower deck routinely, helping keep it fitter for longer.

Remember, keeping a keen eye on your machine and maintaining it meticulously ensures a prolonged life for your lawn mower. Adopting these steps empowers you to deal efficiently with common problems and ensure smooth and seamless operation.