When it comes to mowing the lawn, there’s nothing more frustrating than having your mower quit in the middle of your yard on a hot sunny day. There are many items that you can easily troubleshoot and repair yourself. However, there are items, such as engine and charging system problems, that may be better diagnosed by an experienced mechanic.
A riding lawn mower may quit when hot because the air filter is plugged; the fuel system is clogged; the oil level is too high or too low; air isn’t circulating around the engine block; the spark plug is bad; the ignition coil is faulty; or there is debris buildup under the deck.
Always follow the safety precautions outlined in your operator’s manual before working on your riding lawn mower to prevent injury.
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Follow all safety instructions provided in your equipment operators manual prior to diagnosing, repairing or operating. Consult a professional if you don’t have the skills, knowledge or are not in the condition to perform the repair safely.
11 Reasons a Riding Lawn Mower Shuts Off When Hot
Plugged Air Filter in a Riding Lawn Mower
Your riding mower’s engine requires air to start and run. Without air, the mower will shut down. So, if you’ve been mowing for a while and the mower just quits, one of the first items you should check is the air filter.
Because the mower is run in dusty conditions where grass clippings and dirt are tossed in the air, the filter can become plugged. If you don’t frequently remove and clean your filter during the mowing season, it can buildup with so much dirt and debris that air cannot pass through the filter. The lack of air will cause your riding mower to overheat and shut down.
It is best to start out each mowing season with a clean air filter. Check and clean the filter at least a couple times throughout the season to keep it free of debris so your engine keeps running at its best. You will need to check it more often when mowing in dry dusty conditions.
Cleaning your riding mower air filter is a simple task. A neglected air filter can contribute to internal engine damage and costly repairs.
FIX: To clean your paper air filter by following these steps:
- Remove the air filter from the housing.
- Wipe out any dirt remaining in the housing. Don’t allow the dirt to fall into the air intake.
- Tap your air filter against a solid surface to loosen the dirt and remove as much as possible.
- Hold your filter up to a light to check for light shining through the paper.
- Reuse the filter if you can see light shine through the paper element. Replace with a new air filter when you cannot see light.
- Reattach the air filter cover.
Bad or Old Fuel in a Riding Lawn Mower
Gas that has been sitting around can begin to breakdown and become less effective as quickly as 30 days after purchase. Ethanol, used in most gasolines today, is a corn-based fuel that attracts moisture from the air. This moisture will cause corrosion of the fuel system and leave gummy fuel deposits behind resulting in restrictions.
To avoid many of the problems that result from using the wrong kind of fuel or old fuel, use an unleaded gasoline with a minimum octane-rating of 87 and maximum ethanol content of 10%. Read more about the right gasoline for your riding mower here. Use a fuel additive to stabilize the fuel.
If your lawn tractor is diesel-powered, you may run into the similar types of fuel problems with moisture buildup causing corrosion in the fuel system along with sediment buildup. A fuel additive can also be added to diesel fuel to stabilize and reduce moisture.
FIX: Drain the fuel tank using a siphon to remove old fuel from your tank and place it in an approved container. Fill your riding lawn mower with fresh gasoline that contains a fuel additive to stabilize and clean your fuel system.
I recommend a product called Sea Foam Motor Treatment for your riding lawn mower because it has cleaning agents for the engine and the fuel system. It isn’t only better for the carburetor, it is also good for the valve train as well. Read more about the advantages of using Sea Foam in your fuel system in my article here.
If you still have a clog in your fuel system after changing your fuel and using a fuel system cleaner, check out my article on why a riding lawn mower isn’t getting fuel for other items to check on your mower.
Dirty Carburetor on a Riding Lawn Mower
A riding mower requires a carburetor to regulate the about of fuel that gets mixed with air to form a combustion in the cylinder. It is common for a carburetor to become dirty from old fuel clogging components of the carburetor including the fuel jet.
Old fuel leaves gummy and crusty deposits affecting the carburetor’s function that may shut down the mower after it has been running for a while.
FIX: Before you start tearing the carburetor apart, make sure fuel is getting to the carburetor. Next, remove the air filter, spray carburetor cleaner in the air intake and start your mower. If your mower starts and then shuts down, it’s time to take apart your carburetor to clean or rebuild it.
If you are a little mechanical and don’t mind working with small parts, you should be able to disassemble and clean your riding mower carburetor following the instructions in this guide.
Unsure about tackling the cleaning of your carburetor? Have your local lawn mower repair shop clean it for you. Another option to fix your carburetor issues is purchasing and installing a new carburetor.
Wrong Engine Oil in a Riding Lawn Mower
It is best to use an air-cooled engine oil that contains a high concentration of zinc in a gas-powered riding lawn mower. Zinc is an additive used as a cooling agent. This type of oil varies from oil used in cars. A car uses water in a liquid to cool the engine while a riding lawn mower uses air to cool its small engine.
Most lawn mower small engines manufacturers recommend using an SAE30 or 10W-30 engine oil. You may need to change your oil viscosity to a 20W-50 when operating in higher ambient temperatures. Use this chart along with your owner’s manual as reference to select the correct engine oil for your riding mower so it doesn’t result in overheating your engine.
FIX: Drain the engine oil and fill with the fresh oil using the viscosity recommended by the engine manufacturer.
Too Little Engine Oil in a Riding Lawn Mower
An engine oil level that is lower than the manufacturer’s required level can cause your riding lawn mower to quit when it gets hot. Oil is a lubricant that allows the internal engine parts to move smoothly. Using your riding mower with a low engine oil will cause oil to heat up and thicken resulting in an increased friction among the moving parts.
This friction will cause the heat in the engine to build. This heat can become so hot your the riding mower may begin smoking from oil burning off and engine parts melting.
FIX: You can attempt changing your engine oil and bringing it to the correct level. However, most of the time, once your mower shuts down due to running on low oil, the simple fix of an oil change will not work. Most likely, you have internal engine damage that requires a small engine mechanic to perform tests to properly identify your engine problem.
Regularly checking your engine oil level is a preventative measure you need to take prior to each mowing. A low engine oil can indicate the engine is burning or using oil. It may also indicate you have an engine oil leak. Read more about this in my article on overheating.
Too Much Engine Oil in a Riding Lawn Mower
Most people know not having enough engine oil in the crankcase will cause engine problems, but they don’t always know the same is true of having too much engine oil. Overfilling your crankcase with engine oil will require the crankshaft and rod to push through excess oil and not be able to rotate freely.
Too much oil will increase the crankcase pressure putting the internal engine parts under load. This will cause the engine to quit when it gets hot. Additionally, the engine may run terribly and shut off when excess oil is pushed into the cylinder through the valve train. This oil burns off, creates a smoke and plugs the air filter restricting airflow.
FIX: Remove excess oil so you have the correct amount of oil in your riding mower as specified by the engine manufacturer. Remove the spark plug wire and then drain a little oil using one of the following methods:
- Drain Plug: Quickly remove and replace your drain plug to only remove a little oil
- Oil Filter: Remove the oil filter. Have a rag ready to collect a little oil out of the filter.
- Oil Fill Hole: Some push mowers won’t have a drain plug or oil filter. You’ll have to tip over your mower to remove a little oil out of the oil fill hole. Keep the carburetor and air filter on the high side when tilting your mower.
- Oil Extractor Pump: Use an oil evacuator to vacuum out a little oil out of the oil fill area.
- Turkey Baster: Use a turkey baster to suck a little oil out of the oil fill.
Check the engine oil level and add or drain more oil if needed. Once you have corrected the oil level, check and replace your air filter if it has signs of oil on it.
Damaged or Clogged Engine Cooling Fins on a Riding Lawn Mower
The engine must be kept cool so it doesn’t overheat and shut down. The engine cooling fins help circulate air around the engine block and cylinder to help keep it cool. Plugged or broken cooling fins will compromise the air flow and can be the reason your riding mower quits when hot.
FIX: Remove debris around your cooling fins and replace any broken fins. Remove debris collecting under your engine shrouds and confirm your heat shield is securely in place.
Broke or Dirty Spark Plug on a Riding Lawn Mower
A dirty spark plug in your riding mower can foul causing the engine to run sluggish or quit. It may have produced enough spark to start your mower, but may be unable to keep it running. Remove the spark plug(s) and check its condition.
Look for signs of carbon buildup, a cracked porcelain or a burnt electrode. You can attempt to clean the spark plug with a metal brush to remove dirt and reuse. However, a damaged, excessively dirty or dark spark plug must be replaced.
FIX: When the spark plug wire is loose or the gap is not correct, it may cause intermittent running or starting problems. Make sure your spark plug has the correct gap and the wires are securely attached.
Bad Ignition Coil on a Riding Lawn Mower
When the ignition coil gets hot it can stop working causing your riding lawn mower to shut down. The windings on the coil separate and short out. A faulty ignition coil won’t be able to provide sufficient voltage to the spark plug.
FIX: Use an ohm meter to test your ignition coil to confirm there is no break in the continuity of the coil. Replace when you find a faulty coil.
Bad Fuel Cap on a Riding Lawn Mower
The fuel cap used on a riding mower is designed with a vent to allow air to pass through the cap. Your mower may run for a while and quit when air is prevented to pass through the cap. This is because, without the vent, a vacuum is created in the fuel system preventing fuel from leaving the fuel tank. This can result in the riding mower dying once it has been running for a while.
FIX: Replace your fuel cap if your mower runs while the fuel cap is removed and quits after a short running time with the cap installed. You can try to clean the cap to remove the clog first or just replace it to ensure you have a clog-free cap.
Clogged Mower Deck & Dull Blades on a Riding Lawn Mower
The engine is put under load when the riding mower has a clogged mower deck. Because the engine must turn the mower blades through a bunch of debris with each turn, extra strain is put on the engine that can cause it to quit when it gets hot.
In addition to a clogged mower deck, dull mower blades will further add to the problem causing your engine to overload and shut down.
FIX: Sharpen your mower blades and scrape your deck to keep your riding lawn mower’s cut at its best and prevent the engine from being overworked. Avoid mowing your lawn in wet conditions. Wet grass is more prone to collecting under the deck and clumping in your yard.
Still Having Problems With Your Riding Mower?
As a lawn mower owner, when you own it long enough, you are going to run into different types of problems. This may include problems where you riding mower is smoking, cutting uneven, losing power, not starting, leaking fuel and more.
Check out this handy guide including charts for common riding mower problems and solutions:
Common Riding Lawn Mower Problems & Solutions.
If you are unable to fix your riding mower or don’t want to attempt a more complicated repair, have your local lawn mower dealership or repair shop for assistance.