SOLVED! Toro Lawn Mower Quits When Hot

A Toro lawn mower may quit when hot due to a plugged air filter; old fuel; a dirty carburetor; the wrong type of engine oil; a low or high level of engine oil; plugged cooling fins; a bad spark plug; a faulty ignition coil; a plugged mower deck, or a plugged fuel cap.

Follow the safety precautions in your Toro operator’s manual. This includes waiting for the engine to cool and removing the ignition key (if the mower uses one) and the spark plug wire(s).

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Follow all safety instructions provided in your equipment operator’s manual before diagnosing, repairing, or operating. Consult a professional if you don’t have the skills, or knowledge or are not in the condition to perform the repair safely.

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Reasons Your Toro Lawn Mower Quits When Hot

Plugged Air Filter

When your mower quits after it gets hot, check the air filter. The air filter is required to keep dirt from entering the air intake and damaging the engine.

While the air filter is meant to protect the engine, it can also cause the mower to die when routine maintenance isn’t performed to keep the filter clean.

When the air filter becomes extremely dirty, it can keep a good flow of fresh air from passing through the filter. The lack of air will cause the engine to shut down and possibly overheat due.

I recommend starting each mowing season with a new air filter. Follow this by checking the filter regularly and cleaning it when needed.

However, if you use your mower for commercial purposes, more than the average homeowner, or in very dusty conditions, you’ll need to clean and replace it more often.

SOLUTION: Clean the air filter to keep it in good condition. NEVER run a mower without an air filter.

Clean a Toro paper lawn mower air filter:

Remove the air filter cover.
Carefully remove the air filter to prevent loose dirt from falling into the air intake.
Wipe out any dirt remaining in the air filter housing. Again, don’t allow dirt and debris to fall into the intake.
Tap your paper filter element against a solid surface to loosen and remove dirt. Get as much dirt out as possible. Do not use compressed air to clean the filter as this will damage it.
Hold your filter up to a light source to check for light shining through the paper.
Reuse a filter where you can see light through the paper. Replace with a new air filter when you cannot see light or the filter is wet, damaged, or very dirty.
Install the filter into the air filter housing and reattach the filter cover.

Clean a Toro PRE-FILTER foam lawn mower air filter:

*The foam pre-filter is used in conjunction with some paper air filters. Don’t confuse a pre-filter with a primary foam filter. DO NOT add oil to a foam pre-filter used with a paper air filter element.

Inspect the foam pre-filter to ensure it is in good condition. It must not have any tears, be brittle, or have dark spots forming on the filter. Replace it if it is not in good condition.
Clean the filter using mild detergent and water. Rinse the filter until the water runs clear and all soap has been removed.
Squeeze the filter to remove excess water. Don’t wring the filter as this may tear it.
Lay flat to dry.
Install the filter once dry.

Old Gas

Running fresh gasoline through your mower with a low ethanol content will reduce the fuel and engine problems you experience due to old fuel. These problems include fuel restrictions that cause the engine to die after running for a while.

Ethanol found in most gasoline attracts moisture to the fuel system. When this ethanol and water mixture evaporates, it can leave behind a sticky substance that clogs the fuel system and damages fuel components.

In addition, the mixture will separate from the gas and sink to the bottom of the fuel tank. This mixture can cause the engine to quit.

Toro lawn mowers require unleaded gasoline with a minimum 87-octane rating and maximum 10% ethanol content. The lower the ethanol the better. Ethanol-free fuel is best.

SOLUTION: Drain the fuel tank into an approved fuel storage container using a siphon pump. Fill the lawn mower with fresh fuel and an additive to clean and stabilize your fuel.

I recommend a product called Sea Foam Motor Treatment. It is a petroleum-based product that won’t hurt your engine. It contains cleaning agents for your engine and fuel system. Read more about why I prefer Sea Foam here.

* If you own an old Toro push mower, the mower may use a fuel consisting of a gas and two-cycle engine oil mix. Read about push mower gas to learn more.

Dirty Carburetor

A combustion is formed in the cylinder with the right amount of air, fuel, and spark. The carburetor is responsible for regulating the amount of fuel that mixes with air.

Old gas can leave behind varnish that clogs passageways and causes small parts to stick so the carburetor no longer functions right. A lack of fuel from the carburetor will cause the mower to quit.

When the carburetor becomes dirty and fails to work properly it must be removed and cleaned.

Before tearing the carburetor apart to clean it, perform a couple of steps to confirm your running problem lies with your carburetor. First, make sure you are getting fuel to the carburetor.

Second, remove the air filter and spray carburetor cleaner into the air intake. Start your mower. If it runs for a bit and then shuts down, you will need to disassemble your carburetor and clean it.

SOLUTION: If you are a little mechanical and don’t mind working with a lot of small parts, you should be able to handle cleaning your carburetor. Follow the instructions in this article to clean the carburetor on your lawn mower.

You can also have your local lawn mower repair shop clean the carburetor if you choose to not tackle the task yourself.

Wrong Type of Engine Oil

The best kind of engine oil is air-cooled engine oil which contains a high concentration of zinc. Zinc is used as a cooling agent.

The cooling procedure differs from cars. Cars use liquid to cool their engines and small engines use air for cooling. Most lawn mower small engine manufacturers recommend using SAE30 or 10W-30 engine oil.

While this is the recommendation and good for most areas, you may have to change to using a different viscosity, like 20W-50 when operating in higher ambient temperatures.

Use this chart provided by Kawasaki Motors along with your operator’s manual to select the correct engine oil for your lawn mower.

Running the wrong engine oil can result in overheating your engine causing it to shut down.

kawasaki air cooled engine oil chart — Kawasaki Oil Viscosity Chart

SOLUTION: When you find the engine oil is not correct, drain the oil and fill it with the appropriate fresh air-cooled engine oil.

Low Engine Oil Level

Before each use, you should check the lawn mower’s engine oil level. Running with low engine oil can cause your mower to overheat and shut down. Oil is used to lubricate the internal engine parts.

Without enough oil in the crankcase, friction will build among the moving parts creating heat. This heat can become so hot, oil and parts begin to burn to result in significant engine damage.

SOLUTION: You can attempt to correct the engine oil level and try to start your mower to see if it runs. Most likely, once your mower shuts down due to a low engine oil issue, you have already caused extensive engine damage.

Have an experienced small engine mechanic perform tests on your engine to determine the extent of the damage. Running a Toro mower with a low oil level can result in needing an engine replacement.

Too Much Engine Oil

Most people know not having enough oil in the crankcase can cause engine damage, but they aren’t always aware too much oil can also create engine problems.

Overfilling the crankcase with engine oil causes increased pressure in the crankcase.

It causes the crankshaft and rod to not move freely because they have to push through excess oil. This can put the internal engine parts under load causing the engine to get hot and quit.

In addition to this, running too much oil in a mower can push oil into the cylinder through the valve train causing a thick cloud of smoke when the oil burns off.

This smoke can plug the filter and start the engine of air making it shut down.

SOLUTION: Remove excess oil to bring it to the recommended oil level as indicated on the oil dipstick. Before you start, disconnect the spark plug wire(s) so your engine doesn’t start.

You can drain a little oil through the drain plug, oil filter, or oil fill hole. You can use an oil evacuator or turkey baster as well to pull a little oil out of the engine oil fill.

Once you have drained a little oil, check the level and drain or add more oil as needed to bring to correct your engine oil level.

Check your air filter to make sure it isn’t plugged from the smoke if your mower started to smoke before it quit. Reattach the spark plug wire(s).

If you still experience problems after correcting your engine oil level, have an engine mechanic check it out. Read this article for more information on running your lawn mower with too much oil.

Damaged or Clogged Engine Cooling Fins Cause a Toro Lawn Mower to Quit

The cooling fins help dissipate air to keep the engine block and cylinder cool. The cooling fins should be cleaned annually and kept free of debris that will prevent it from circulating air around your engine.

When the engine isn’t kept cool, it can overheat and quit.

SOLUTION: Remove debris around your cooling fins and replace any broken fins. Remove any dirt collecting around your engine shroud and make sure the heat shield is firmly in place.

Bad Spark Plug

A dirty spark plug that has carbon buildup, broken porcelain, or burnt electrode can fail and cause your Toro mower to stop. It may have provided enough spark to start your mower, but now it can’t keep it running.

SOLUTION: Check the plug for signs of buildup on the tip and clean it if necessary. If you find the tip to be extremely dark or find damage, you must replace your spark plug.

Check your spark plug wires and make sure they are securely attached as this can also cause your mower to quit running.

Bad Ignition Coil

When the ignition coil gets hot, it can stop working causing your lawn mower to quit running. The windings on the coil can separate and short out.

A bad ignition coil will not be able to provide sufficient voltage to the spark plug.

SOLUTION: Use an ohmmeter to test your ignition coil to confirm there isn’t a break in the continuity. Replace the coil when you find your ignition coil is bad.

Clogged Fuel Cap

A gas cap is designed to let air pass through the cap so the fuel tank can vent. The cap can become plugged and no longer allow the air pressure inside the tank and outside the tank to equalize.

When this happens, the fuel tank forms a vacuum keeping fuel from flowing out of the fuel tank to the carburetor. This can cause your mower to die after it has been running for a while.

SOLUTION: Check the condition of your gas cap by allowing your mower to run with and without the gas cap. If the mower eventually shuts off when the cap is in place, but runs fine when it isn’t in place, you most likely have a problem with your fuel cap.

You can attempt to clean out your fuel cap to try to remove the plug. I choose to replace mine with a new gas cap.

Plugged Mower Deck & Dull Blades

A mower deck can become packed with grass clippings and debris when it isn’t periodically scraped and kept clean.

The engine must work harder to turn the mower blades through the plugged deck. Running your mower with dull mower blades further magnifies the problem.

SOLUTION: Scrape the deck periodically and sharpen your Toro mower blades. Not only does it provide a better cut, but it also prevents an overload on your engine.

Prevent the amount of grass buildup by not mowing in wet conditions.

Still Having Problems with Your Toro Lawn Mower?

It would be great to own a problem-free lawn mower, but it’s never the case. No matter what brand mower you own, you’re going to run into problems the longer you own it.

To help you troubleshoot your mower problems, I have put together a list of common problems along with causes and solutions to fix them. Check out Common Toro Lawn Mower Problems and Solutions to learn more.