Lawnmower won’t start when hot, what to do. Diagnose&Fixes

On a nice day you take your trustworthy lawn mower outside with the intention to trim your lawn. But somehow your Lawnmower is not running smoothly. You discover that it starts and runs fine when cold. However, starting it again when it is hot is an awful experience.

So the question is why is the mower difficult to start when hot? The main culprit is presumably a failing coil, but there can be other reasons as well. In this article, we will look at the various reasons and how to resolve the situation.

Lawnmower won’t start when hot:

• A Defective Spark Plug not igniting the fuel
• High/Low oil level
• Flawed fins foundation of Overheated Engine
• Loose nuts and bolts become the basis for leakage of air, causing insufficient air supply to the combustion.
• A restricted Carburetor due to a faulty auto choke causing engine flooding
• Problematic Compression due to inoperative valve
• Presence of alcohol in oil.
• Faulty ignition coil.

If you are unsure how to troubleshoot the problem, we have broken down the steps in simple and user-friendly instructions.

Common troubleshooting steps when your lawnmower does not start when it is hot:

We have identified seven reasons why your Lawn Mower will not, or is difficult to start when it is hot.

1. Defective Spark Plug

One of the most common causes of lawnmower engine not cranking is due to a faulty spark plug. There is a minimal gap between the two electrodes of the spark plug. It ignites across that gap and aids the proper air -gasoline mixture to combust and produce power. If this gap does not fulfill the optimum length requirement, the combusted heat widens the gap enough to shut down the mower. The spark plug’s spacing should be fixed according to the details given in your Lawnmower’s manufacturing manual. Moreover, the electrode can also weaken due to wear and tear.

Secondly, the buildup soot can also affect spark creation, and this incomplete ignition gives a hard time for the engine to start when hot. The hot start failures are mostly due to the wrong plug fitting. As we already know that the lengths and heat ranges are specified for spark plugs. Initially, you must inspect the correct plug code with your engine maker. It is an excellent practice to have a spare spark plug with you as it permits you to fix your problem swiftly by restoring the plug with a good one. After examining the sparking plug, if you find its components are not smooth, you will see that the issue is resolved, and your time is saved just by restoring the plug.

You can also not repair a defective spark plug; it is recommended to replace your spark plug at the start of every season.

2. Faulty plug wire

Plug wires are copper coils looped around a metal core. They work as the high voltage passes through them, searching for ground; positive voltage bounces from the plug electrode to the ground. The spark plug provides a perfect path to ground the voltage and spark ignites. This process took a couple of milliseconds. If we provide a relatively shorter path to the ground for the coil voltage, it will eventually shut down the mower engine because the voltage is not reaching the plug.

Therefore, when we emancipate the bail lever, the coil voltage achieves an ideal track to ground, the engine shuts off suddenly. And everyone wants a short cut whether it is human or machine. The engine will not run intermittently if any abrasion is faced by coil control wire against the ground source.

When the engine starts, massive combustion occurs; high-temperature values cause’ high resistance to the voltage flow, which is why plug wires generally breakdown when the mower is hot and begins operating again when the engine cools down. A precautionary measure always keeps your lawn mowers in ventilated areas because the greatest enemy of plug wire and electrical components is moisture.

3. Malfunctioned Carburetor

Your engine requires fuel or is getting too much air in a failing carburetor, which is the biggest obstacle in its smooth running? We’ll try to figure it out here.

– Does the engine gets enough fuel

Let us check whether the engine is lacking fuel or not. Lawnmowers may be fitted with different choke types (auto choke, manual choke, or a priming bulb) to start a cold engine and smoothly enrich the fuel mixture. Usually, the auto choke carburetors are prone to supplying extra fuel to the cylinder when starting hot; this phenomenon floods the spark plug with fuel that leads to a no start.  The gummed-up and sticky choke located inside the Carburetor is another cause for the hindrance in the starting engine, as it fails to provide the proper fuel ratio. Because it malfunctions, the engine stops working.

– Does the engine gets enough air

Another origin is the lack of ample air or provision of extra air for the flooded engine. The auxiliary air could be from a vacuum leak somewhere in the engine or a carburetor fault, whereas the air’s absence might be due to clogged air filters. For the appropriate AFR, remove the air filter and clean the air filters and chokes; otherwise, the air-fuel ratio is off. Gas engines perform their best when the air-fuel ratio is 14.7 to 1 that mean 14.7 parts of air to 1 part of fuel.

Most lawn mowers will typically have a lever to sway choke; advanced engines now offer a thermostatically controlled automatic choke system. So if you have an engine (auto-choke) with a hot start problem, go ahead and change the Carburetor. It is good to check the choke linkages, thermostat if exits, and clean the choke and air filters. If any of the elements has gone wrong, then the engine will stop. So, it is better to replace the faulty components if cleaning is not successful.

4. Low oil level

Engine components like coils and plugs will stall when they are above the optimum temperature limit, and the low rise in engine temperature is observed when the oil level is low.  Also, an initial start or push cannot be generated if the engine has a critically low oil level to protect the engine because it serves as a basis of coolant and lubricant in the engine. So, whenever you fill the gasoline, make sure you have checked the oil level.

5. Overheated Engine

Another frequent cause of motor engines not starting when hot is the overheated engine. The lawnmower engine may look small, but it generates a tremendous amount of heat when in operation. To dissipate such extreme heat, it has cooling fins. The sole purpose of the fins is to scatter the inoperable heat. However, when you mow the lawn, the grass clippings and other debris may clog or block the fins. These fins jammed with old grass stuff and debris for an extended period behaves like an insulation blanket, in return overheating the mower.

It will eventually stop running, and you will have to wait until the engine cools. The shroud or plastic housing can also trap enough dirt, debris, twigs, and clogs that will eventually lead to the engine shut off. Therefore, cleaning the fins and plastic covers once it is cool prevents the engine from stalling. What you have to do is take away the outer casing of plastic and eradicate the twigs and old grass with compressed air; otherwise, they become the prime source of holding heat close to the engine. When the engine cools, fire it up again, but it perhaps will bog down and stop once more after it overheats.

6. Air leaks

Loose bolts are commonly the source in a mower engine for shutting down when hot. Let me explain how. Loose bolts are a source of air leaks that force an engine to sucks in too much outside air, which abandon the appropriate gas-to-air ratio. When the engine gradually heats up, the remote units expand, and all gaps become larger. Ultimately, you came across the hard running of the engine that will sooner or later shut off.

Therefore, periodically you have to tighten the bolts that keep the motor frame and engine components together to avoid this problem; otherwise, these bolts will probably lose after their overtime use and make the engine of your mower shut off. Check and tighten the bolts, especially those that are linked with the air intake to the engine block. An important tip to check at times the bolts that secure the whole lawnmower frame.

7. Problematic Compression 

The compression issue is prevalent for mowers. It is mostly due to faulty valves. There is an easy way to figure out whether your mower is suffering from low Compression or not. If the mower’s starter rope seems to move easier than it used to be, it indicates the Compression is inadequate along with too large valve clearances, which is the foundation for another problem aggravated by a hot engine. If you do not know about mechanical components, you need to call a professional small engine repair person.

You can refer to a video as attached in this URL that explains the entire process:

Additional causes when your lawn mower does not start when it is hot:

Apart from the earlier mentioned reasons, there are two additional reasons that can lead to your mower not, pr difficult starting when it is hot.

● Presence of Alcohol in oil.

Sometimes, alcohol in oil may be responsible for shutting off. Many manufacturers recommend regular gas or e10 ethanol. As E15 and e85, when set on fire, dissipate much heat, it will damage the engine because of the low boiling point. And it voids your warranty. You can solve the problem by merely placing a riser or non-metallic shim between the engine and the carb.

● Troublesome ignition coil

If your Lawnmower is new, though it is rare but possible, the ignition coil may have gone wrong. But if the mower is 10+ years old, the chance is high. The ignition coil and condenser control the flow of electricity to the spark plug. They must be in the best state, and if they are not, they should be replaced on a priority basis; otherwise, it can cause severe problems in starting the engine.

Frequently Asked Questions:

1. Starter does not crank when hot, what to do?

This issue is the case of heat soaked. It is merely a matter of absorbing and retaining heat from underwater sources, for instance, from the exhaust. This heat adds up the resistance in the starter’s electrical component, which dramatically reduces the current flow. The limited current in the starter results in improper cranking. Diagnose the battery, cables, and starter before the operation.

2. Why Honda lawnmower won’t start?

First of all, inspect the spark plug to see if it is damaged by using a spark plug tester. When the engine is cranking, if there is a vital spark, then the spark plug terminals are not defective and vice versa. Replace the spark plug if it’s defective.

 A clogged carburetor can restrict the engine from starting, so replace it if it’s not working after cleaning. Insufficient or old fuel (gasoline) may be one reason for carburetor clogging; some components may evaporate with time leaving behind a stickier fluid that causes clogging. Old fuel also causes clogging of the fuel filter. You should check the ignition coil with an ignition coil tester for this issue, replace it if defective.

3. Torro lawnmower is not starting; what to do?

You should do a thorough cleaning of the mower if your Torro lawnmower is not starting. Do clean your mower’s Carburetor, and at the bottom of the float valve, there is a bolt; pull it out. Clean the tiny holes in that jet and make it sure by passing a wire through the holes. Also, clean the very tiny hole at the brass bolt’s top, which often gets clogged.

Final Remarks:

Indeed, a malfunctioning mower can be a significant source of distress. Being impatient in this case will not help you at all. Follow the systematical approach to solve the problem by checking every possibility mentioned above.

The troubleshooting in the steps, as mentioned above, thoroughly takes you through all the issues. Moreover, you will be furnished with the knowledge of what a repair person may need to resolve. 

Impact of Alcohol Presence in Fuel on Engine Shutdown

Presence of alcohol in the fuel – not many vehicle owners know of this potential problem. It’s a factor that can lead to the perplexing phenomenon of engine shutdown.

While alcohol-based fuels, such as E85 (a blend of gasoline and ethanol), can offer benefits like reducing carbon dioxide emissions and dependence on fossil fuels, they present unique challenges to a vehicle’s engine.

• Detrimental Effects of Alcohol-based Fuels

Alcohol-based fuels, which contain a high concentration of alcohol, can negatively affect engine performance. For example, using a high concentration of alcohol in the engine can lead to corrosion of metal parts, degradation of plastic and rubber components, and accumulation of water in the fuel system.

Alcohol’s nature allows it to absorb water from the surrounding environment. When mixed with fuel, it can potentially cause phase separation. The heavier water-alcohol mix settles at the bottom of the tank, while lighter fuel floats on top.

This situation can result in water being drawn into the fuel system, leading to poor engine performance and, eventually, an engine shutdown.

The U.S. Energy Information Administration (EIA) further highlights that ethanol, a popular type of alcohol found in some fuels, can cause stress to the fuel system. When this happens, the engine may not start, or it could shut down altogether.

• The Hot Start Issue: Troublesome Ignition Coil

Dealing with a car that won’t start is something all drivers dread. Unfortunately, a commonly overlooked cause of this problem is a hot start issue. The core reason behind this lies within a troubled ignition coil.

• Understanding the Ignition Coil

The ignition coil plays a key role in starting your vehicle. It transforms the battery’s low voltage to the thousands of volts needed by the spark plugs to ignite the fuel and start the vehicle. A failing or malfunctioning ignition coil can present various symptoms, such as poor fuel economy, engine misfires, and even stalling.

• Spotting a Malfunctioning Ignition Coil

A car exhibiting hot start problems can be indicative of a faulty ignition coil. This often results in a car starting fine when the engine is cold, but when the engine has run for a while and is switched off, a repeated attempt to start it may fail.

This temperature-dependent behavior can be traced back to the ignition coil. As per CarTalk, a .org website devoted to simplifying complex car issues for ordinary users, the solenoid in the ignition system could be getting too hot and not engaging properly, leading to hot start issues.

• Overheating of ignition coil

An ignition coil that gets too hot is also a sign that it’s malfunctioning. The coil could be getting too hot due to resistance or wire connection problems. Debris that gets trapped around the coil may also affect the temperature.

As a vehicle owner, it is crucial to understand these issues. Identifying potential problems quickly can let you address them before they lead to more severe damage or cause your vehicle to break down completely.

Keep a close eye on your fuel choice, and always ensure your ignition coil is in good working condition. Such practices will help maintain your engine’s prime health, promising smoother rides and significantly lesser garage visits.

• Importance of Regular Oil Check-up on Lawnmowers

Maintaining a constant oil level in your lawnmower engine is paramount. Negligence in this action could catalyze unforeseen complications, especially on hot engines.

A quick routine check on the oil level can save you from a lot of head-scratching when trying to start the engine. From my experience, sticking to a regular check-up of oil levels is one key factor in maintaining a smooth-running lawnmower.

• Alcohol in Lawnmower Oil: An Overlooked Problem

While many may be unaware, alcohol in lawnmower oil can cause the engine to shut off unexpectedly. As such, it’s recommended to use regular gas or E10 ethanol. One should steer clear from fuels with high ethanol content, like E15 or E85.

They reduce the lawnmower’s efficiency, and honestly, it’s a minor change that can make a major impact.

• How Moisture Damages Lawnmower Components

Humidity is a silent yet significant destroyer of lawnmower parts. It has the potential to damage electrical components, such as the plug wire and the ignition coil.

Therefore, well-ventilated storage space is crucial for the longevity of your lawnmower by avoiding moisture accumulation. The University of Illinois Extension provides some great tips on how to properly store and maintain your lawnmower to prevent moisture-related damage.

• Honda Lawnmowers: Troubleshooting Starting Issues

Honda lawnmower owners often grapple with starting problems caused by a faulty spark plug, clogged carburetor, or defective ignition coil.

Early diagnosis and addressing these specific issues promptly can save you from major lawnmower troubles. I cannot stress enough how important timely intervention can be.

• Resolving starting issues with Toro Lawnmowers

Many Toro lawnmower owners find their machines not starting, and this can be quite stressful. Often at times, just cleaning out the carburetor and ensuring that the jets and other small holes are not clogged does the trick. Remember, prevention is often better than cure.

• Dealing with Heat Soak in Lawnmowers

Heat soak is a frequent troublemaker in lawnmowers. When the engine becomes hot, it can prevent the starter from cranking. Common culprits behind this issue are excessive under-hood heat sources, like the exhaust.

A thorough check of the battery, cables, and starter can help diagnose and resolve these starting problems. Remember, a reliable lawnmower is a well-inspected one.

Throughout my years of experience, these issues have persisted across multiple brands and models of lawnmowers. Staying on top of your regular maintenance and understanding these problems can extend the life and efficiency of your equipment.

Whether you own a massive John Deere tractor to mow your fields or a small Toro to manage your backyard, these tips apply to all. Remember, a well-cared-for lawnmower is the first step toward a well-cared-for lawn.

• Faulty Fuel Pump: A Possible Cause for Lawn Mower Starting Woes

When your lawn mower refuses to start when hot, one of the problems could lie in a faulty fuel pump. The fuel pump is critical in delivering gas from the tank to the carburetor; it needs to be functioning optimally for your lawn mower to work well.

If it’s defective, it could prevent the engine from getting the necessary fuel to run. The University of Florida provides an excellent guide to understanding and maintaining your lawn mower.

• Dirty Air Filter: An Overlooked Obstacle

In my experience, a dirty or clogged air filter can severely impede the smooth operation of your lawn mower. A lawn mower relies on a mixture of air and fuel to run. If the air filter is dirty, it will block the required air, thus upsetting this delicate balance and possibly causing starting issues.

• Importance of Spark Arrestor Screen Maintenance

Regularly inspecting and cleaning the spark arrestor screen can go a long way in ensuring proper airflow and preventing overheating of your mower.

The spark arrestor screen prevents hot, burning particles from escaping the combustion chamber. When it becomes clogged over time, it could lead to airflow issues and potentially overheat your machine.

• Possible Causes: Faulty Ignition Switch or Wiring Issues

A fault in the ignition switch or wiring could also be why your lawn mower won’t start when hot. Electrical faults may prevent the spark necessary to ignite the fuel, causing starting problems.

• Cooling Fins and Plastic Housing Upkeep

Another crucial aspect of lawn mower maintenance involves the cooling fins and plastic housing. Cleaning and maintaining these parts help regulate the engine temperature, ensuring that it doesn’t overheat while mowing. It can make a considerable difference in the overall operation and lifespan of your garden tool.

• Frequent Oil Changes for Efficient Engine Cooling and Lubrication

I cannot stress enough the importance of regular oil changes and using the recommended type of oil for your mower. Engine oil is essential for engine cooling and lubrication.

Without the necessary qualities of sufficient and quality engine oil, friction between moving parts increases, leading to overheating and significant engine wear.

• Carburetor Float and Needle Valve Problems

A carburetor fault, particularly in the float or needle valve, could cause flooding and make starting your hot lawn mower a real headache. This component controls the amount of fuel distributed to the engine and if faulty, could lead to flooding and start-up difficulties.

• Impact of a Worn or Damaged Piston Seal

A worn or damaged piston seal can impact the compression. Essential compression for effective ignition of the fuel can be compromised, thus preventing your hot lawn mower engine from starting.

• Environment Matters: Clean and Dry Storage

Last but not least, storing your lawn mower in a clean, dry environment is critical in preventing moisture damage to electrical components. I have found that this simple precaution can notably extend the life of your lawn mower.

By focusing on these aspects, I believe one can significantly improve the longevity and reliability of their lawn mower, ensuring it always starts up seamlessly, regardless of whether it’s hot or cold. After all, a well-maintained mower makes for a well-kept lawn.

Regular Maintenance of Lawnmower

Regular maintenance of your lawnmower is crucial for its performance, especially during hot weather conditions.

Routine cleaning prevents debris, dust, and grime from building up, which could affect your lawnmower’s ability to start efficiently. I recommend maintaining a regular cleaning schedule to ensure optimal performance.

• Importance of Spark Plug Maintenance

The lawnmower’s spark plug plays a significant role in enabling the unit to start smoothly. A worn-out or damaged spark plug can cause issues, particularly in hot weather.

Check the spark plug gap periodically and replace it if it’s damaged. Consider also inspecting the ignition coils and condensers as replacing these components will further enhance your lawnmower’s start-up capability.

• Addressing Carburetor Problems

The lawnmower’s carburetor is another crucial component that can influence your lawnmower’s ability to start.

Over time, the carburetor, including the choke and electronic solenoid, can attract dust and grime, leading to starting problems. Regular cleaning and checking of these parts can help improve starting efficiency.

• Overheating Engine Issues

Overheating is a common issue, especially in hot weather. Clogged cooling fins or plastic housing can cause the engine to overheat, leading to your lawnmower stopping mid-way during operation.

It’s vital to regularly check for any blockages and ensure that the cooling fins are cleaned to prevent overheating issues.

• Importance of Tightening Bolts and Checking for Air Leaks

Loose bolts and air leaks can influence the efficiency of your lawnmower. Not only can this lead to shut-off issues when hot, but it can also lead to more severe engine damage. Therefore, it is essential to regularly tighten bolts and check for air leaks in the engine.

• Checking Oil Level Regularly

Lawnmowers require an adequate level of oil to operate efficiently. Low oil levels, especially in hot weather conditions, can cause starting issues. Therefore, it is advisable to check the oil level before each use of your lawnmower.

• Avoiding Alcohol in the Oil

Certain types of oil contain alcohol, which can disrupt the lawnmower’s operation and cause it to shut off. A common solution is to use a non-metallic shim to address this concern. Proper knowledge of the oil used in your lawnmower can greatly enhance your lawnmower’s performance.

• Crucial Troubleshooting Steps

The troubleshooting steps in this article cover a wide range of common issues that may cause your lawnmower to have starting issues in hot weather.

From spark plug and carburetor maintenance to checking oil levels and avoiding alcohol-based oil, these recommendations will greatly assist in maintaining your lawnmower’s top-notch performance.

For further information on lawnmower maintenance, I suggest checking resources like The Lawn Institute, a non-profit organization focused on lawn maintenance education.

Remember, consistent maintenance is the best way to prevent these issues from arising. Regular checkups of your lawnmower will extend its lifespan and ensure it operates efficiently in all weather conditions.

Checking the Fuel Filter: The Root of Hot Engine Starting Problems

In your struggle with hot engine starting problems, your first suspect should be a clogged fuel filter. This often-overlooked component plays a crucial role in ensuring the smooth flow of fuel to your engine.

A clogged fuel filter restricts the fuel supply, making it difficult to start a hot engine. Regular checking of the filter can help unearth any underlying blocks, leading you closer to the solution.

• Regular Maintenance: Avoid Hot Engine Starting Issues

Your engine functions effectively largely due to the regular care you afford it. Pay particular attention to your air filter – maintaining its cleanliness can ward off a multitude of problems, including starting issues. The air filter ensures that the engine receives an apt airflow, enabling it to work effectively.

Ensuring regular maintenance of your air filter can help prevent any hot engine starting issues right at their onset.

• Dealing with a Sticky Choke: An Adjustive Approach

If you’re dealing with a sticky choke, there’s a fair chance it can lead to hot engine starting problems. How do you deal with this? Quite simply, by adjusting the choke linkage.

Alternatively, you could check for any debris causing the choke to stick and clean it up for smooth operations. An optimally functioning choke can significantly enhance your engine’s performance.

For a detailed guide on adjusting choke linkage, the University of Hampshire’s Mower Maintenance Guide may help.

• The Role of Fuel: Fresh and Clean for best results

Be wary of the fuel you use in your mower. Stale or contaminated fuel is a breeding ground for starting problems, particularly with hot engines. Regularly re-fuel your mower with fresh, clean fuel for improved performance.

If you’re not planning to use your mower for a while, consider using fuel stabilizers or draining the fuel system altogether to prevent fuel-related problems.

• Cleaning Cooling Fins and Plastic Housing: Step-by-Step

The blow of hot engine starting problems can be significantly softened by maintaining cleanliness. Regular cleaning of your mower’s cooling fins and plastic housing can enhance its performance and longevity.

You could take advantage of compressed air to carry out this task effectively. Regular cleaning can substantially alleviate the problem of hot engine starting issues.

• Checking and Adjusting Valve Clearance: A Crucial Task

Checking valve clearance regularly should be part of your standard maintenance routine. If you notice any discrepancies, don’t hesitate to make the necessary adjustments. Valve clearance maintenance ensures optimal engine efficiency and helps in mitigating problems associated with hot engine starting.

• Broadening Horizons: Hot Engine Issues across Brands

Hot engine starting issues don’t discriminate among brands. Irrespective of whether it’s a Briggs and Stratton or any other make, the problem remains the same.

Expanding your knowledge horizon in this context can make you more proficient in troubleshooting and understanding different brands and models of mowers.

• Prevention is Better than Cure: Avoiding Hot Engine Starting Issues in Lawn Mowers

Prevention always beats cure – regular maintenance, proper fuel storage, and operating your mower within recommended temperature ranges are crucial. Regular checks and scheduled servicing can help you avoid any hot engine issues in the first place.

Added knowledge and regular care of your equipment can help nip burgeoning hot engine starting issues in the bud before they become an irksome problem. Armed with these tips and advice, you can ensure your mower remains efficient and trouble-free for the long haul.