A lawnmower is an essential device to keep our environment organized and beautiful. Since it is a technical device, it is inevitable to have faults over time. For example, a lawnmower won't restart when hot. Even it won't work when the weather is too cold.

Why does the lawnmower not start when it's hot or cold? There are several reasons why the device fails to restart. Some causes for hot engines are overheated, faulty choke or spark plug, air leaks, low oil level, faulty ignition coil, or carburetor. Some cold engine causes are old or low fuel, clogged fuel lines and air filters, faulty spark plug, dead battery, wrong oil, etc.

In this article, I will discuss two main topics which are almost close to each other. You will learn about "lawnmower hard to start when cold and hot" and additional exciting information.

Lawnmower Won't Restart When Hot

While running the mower, the engine generates heavy heat. When it cannot dissipate the produced heat, it usually stops running. Therefore, it won't restart again till it becomes cool. But you must wait for it and rerun it though there is a possibility that the same problem will happen again.

I am here to explain why a lawnmower doesn't start when it is hot.

Overheated Engine

Several factors are there why a lawnmower engine gets overheated:

• The cooling fins molded into the engine's block can get clogged by the grass clippings and debris.

• The plastic housing covering the top of the lawnmower may also trap dirt to stop the engine and increase its temperature.

• Using the wrong plug or fuel type may also damage the cooling fins that cause the engine to overheat.

• Grass clippings can clog the muffler while increasing the temperature of the engine.

You should remove the outer plastic casing and remove the twigs and debris using an air compressor. Then, start the engine to check if it is working perfectly.

Air Leaks

Air leaks are another reason to stop a lawnmower from working normally after making it hot. If there is any leak in the engine, it will make an entrance for outside air to imbalance the gas-to-air ratio. We all know that the engine gets hot overtime when running the mower. So, when it is hot, the remote units start expanding, and all the leaks or gaps become larger. It will be a process to shut off the engine sooner.

Mainly, loose bolts are why an engine gets air inside it. When air is inside, the engine loses its efficiency. So, you should check out all the bolts and tighten them if necessary. It will help to hold the carburetor in the right place. Again, you should check all the bolts periodically.

Spark Problem

There is a small gap between the two electrodes of the spark plug. The air and gasoline fuel mixture combust when a spark passes that gap. Thus, the lawn riding mower gets its power. Now, the heat of the combustion can make the gap wider if the spark plug length is incorrect. The wider gap will shut down the device. So, you should set the gap in maintaining the mower manual for owners.

If carbon malfunctions the spark plug, the mower may get hot and stop working. So, you should replace the damaged plug. Additionally, it is better to replace the ignition coil and condenser.

Malfunctioned Carburetor

Most lawn mowers have starting problems if they have issues with their carburetors. Generally, a choke inside the carburetor must open while the engine starts. But malfunctioned carburetor has closed sticky choke. As a result, you will have a flooded engine.

You should check all the chock linkages and clean them properly to solve this problem. An electronic solenoid helps in the problem-solving subject in some models or brands. But you should maintain your health to prevent the engine from getting hot.

Oil level

Maybe it's unnecessary to think of an oil level to make the engine hot and disable starting a lawnmower. But few brands may not start or restart if the oil level is lower. So, you should inspect the oil level and fulfill the need for oils.

You may also check the oil regularly when you fill the gas. The lawnmowers can hold 0.6 lt. of 5W30 or 10W30 gas.

Faulty choke

If the choking inside the carburetor causes severe damage, you should not use the lawnmower. Even if you use it, the choke will remain shut when you turn on the engine. Therefore, there will be a flood of fluids in the engine. Unfortunately, the flooded engine causes less heat dissipation and increases the engine's temperature. Sometimes there can be a fire outbreak.

When you identify the choking problem, you should remove the air filter. Then, clean the filter and use it again. If your machine has an automatic choke, I suggest replacing the carburetor. Alternatively, you will need to do the same engine with a primary bulb-type choke and smoke.

Lawnmower Hard to Start when Cold

You can find lots of mowers with unique features and performance. Still, no brand cannot guarantee you that their machines will stay fit for eternity. When you are running the mower on the lawn, it may stop working due to different circumstances.

Sometimes, the lawnmower stops when cold. It can be either an internal reason or the extremely cold weather to prevent the machine from starting again. If you can find out why it is happening, you may fix the problem. Or at least, you may tell the expert or technician what he needs to troubleshoot.

Oil Issues

It is one of the main reasons the mower doesn't work like before. If the oil is colder due to wintery weather, the regular oil flow inside the engine becomes poorer. As a result, the engine cannot get sufficient food for every part of it to run again. This is the reason why most engines require warm-up. Once you warm up the device, the oil will flow at a standard rate without any restriction. Moreover, you should use such oil for an engine that can withstand extreme weather conditions.

Old Gas

If you are using the lawnmower after a long time, there is an increased chance of having stale gas inside the fuel tank. Typically, gas can break down in only 30 days. This breakdown can coat the tank interior. Later, when you turn on the engine, it may reach the engine.

So, you should drain the old gas first. Then, properly clean the gas tank and add some fuel stabilizers. Leaving the gas alone for a long time may also make it bad because of evaporation and oxidation. And harmful gas can harm the carburetor and fuel lines. So, get the tank full of fresh gas after cleaning it.

Clogged Fuel Lines

A blocked gas or fuel line can be a reason for a lawnmower not starting when cold. Hence, it is normal to contaminate the fuel with debris or other things that enter the tank. The contamination causes clogged fuel lines that disrupt the regular flow of fuel. Again, the proper gas to air ratio doesn't help in the right combustion in the chamber.

When you can identify the blocked fuel or gas lines, you should check and unclog them as fast as possible.

Damaged Spark Plug

A damaged spark plug can flood the engine. It may cause a mower starting problem when cold. Again, a faulty plug refers to a plug with a wrong electrode gap. This gap may get dirty soon, and gradually, there will be a carbon build. If you see a blackish tone on the plug, you can consider that it has a carbon build-up.

You can easily clean a dirty spark plug with a metal file or sandpaper. Additionally, you may replace or repair the defective plug using the lawnmower like before. Alternatively, a sparkplug tester can help you identify the bad spark plugs.

Clogged Air Filter

Suppose it's winter and your lawnmower is not starting. Then, there can be a reason why it's not working. The air filters are clogged. So, proper burning of fuel inside the machine does not happen. Experts suggest not to use a mower with clogged air filters. Take the filter and start cleaning it to use it again.

Valve Problems

If the above reasons do not match your lawnmower, you can think of the faulty valve. In general, metal size and shape change when you keep it close to the heat. A valve works in the same way that requires ample heat. If it is a cold environment, the valve will not work well. To remove the valve problem, you can change and replace the old valve of the lawnmower engine.


If your lawnmower fails to work when hot, it is good to use a lawnmower oil cooler. Thus, there is no alternative and most beneficial way of maintaining the health of the lawnmower engine than cleaning it regularly. Also, check the parts to know why the mower won't start when cold.

If they need changes or replacement, you should replace them. Lastly, you may also take help from the experts.