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Cub Cadet Mower Starts Then Dies (12 Reasons)

You’re almost done mowing when your Cub Cadet shuts off in the middle of the yard. All you can think of is how much money it’s going to cost to repair your lawn mower.

You probably didn’t budget for mower repairs so having to spend money is frustrating. No one enjoys spending money to fix their mower.

A Cub Cadet Lawn Mower may start and then die when it is unable to regulate the air-to-fuel mixture required by the engine to form combustion.

This could be caused by a dirty carburetor, bad fuel, plugged air filter, broken fuel pump, plugged fins, or other components that can restrict fuel or airflow

I’ll share common problems that can cause your mower to shut off and how you can complete the repairs to save you time and money. I’ll also let you know when it is time to take your mower to a professional mechanic for repair.

Cub Cadet mower does while mowing

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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.

12 Reasons Your Cub Cadet Dies While Mowing

1. Bad Fuel in Your Cub Cadet Lawn Mower

Did you know most of today’s gas contains ethanol, a corn-based product, that has been developed because it is more environmentally friendly than traditional fuels?

Running fuels with some ethanol content is fine for your car, but it is not good for your Cub Cadet small engine.

Ethanol attracts moisture in the fuel system and will begin to separate from gasoline sinking to the bottom of the tank. Solutions with water and ethanol are damaging to your lawn mower and need to be removed.

To protect your lawn mower from the effects of ethanol, use your fuel supply within 30 days of buying and only buy fuel from a busy gas station.

A fuel additive can be added to your fuel system to stabilize your fuel against ethanol separation and moisture buildup. This solution needs to be added to fresh fuel and cannot reverse the separation that has already occurred.

I recommend Sea Foam Motor Treatment for your fuel system. You can read more about it in Why Use Sea Foam Fuel Additive in a Lawn Mower.

FIX: Drain the fuel tank by removing fuel and placing it in a container for recycling. Flush the fuel tank and fill it with fresh fuel treated with a fuel stabilizer.

I like Sea Foam because it not only stabilizes your fuel but is also a fuel system cleaner. Follow the directions on the bottle for mixing.

2. Wrong Fuel in Your Cub Cadet

There are so many different types of fuel on the market today. It can get confusing to see all of the different colored fuel pump handles (they are not always consistent in color at each fuel station) and accidentally grab the wrong type of gas.

I had a customer tell me he was running the correct type of fuel and that the reason his mower died was the fault of the manufacturer.

After he thought about it, a couple of days later he realized his grandchild grabbed the yellow handle at the fuel pump when filling the gas can.

This happened to be E85 fuel which has an ethanol content of 85%. A fuel with such a high concentration of ethanol will damage the fuel system and engine.

Small engines require unleaded gasoline with an octane rating of 87 or greater. The gas must also contain no greater than 10% ethanol. Read the sticker on the fuel pump that shows both the octane rating and ethanol content percentage to confirm the gas you are using.

Most gas stations will carry fuels with 10% (E10) or 15% (E15) ethanol contents. Avoid using the E15 fuels and especially the E85 fuel that is beginning to appear at more gas stations.

For a more in-depth look at fuel for your Cub Cadet lawn mower, check out my article on Cub Cadet gas

FIX: Drain the fuel tank, flush the fuel tank and fill it with fresh fuel treated with Sea Foam Motor Treatment. If your lawn mower continues to have problems, have a small engine mechanic take a look at it.

3. Cub Cadet Has a Dirty Carburetor 

A dirty carburetor can be the reason your Cub Cadet mower starts and then dies. The deposits left behind by bad fuel can create a buildup in your carburetor. 

The carburetor’s function is to regulate fuel flow and air going into the engine cylinder to create combustion. When it becomes clogged, it no longer is able to regulate the gas and air mixture.

FIX: Most likely the carburetor can be cleaned, but is possible the buildup of deposits can be so bad that you won’t be able to get it clean enough to run efficiently. Note: No matter how hard you try, it is difficult to remove all buildup in your carburetor.

If you are mechanically inclined you can try to clean your Cub Cadet carburetor yourself, otherwise, a lawn mower repair shop will be able to help you. 

If you don’t want to try to tackle cleaning your Cub Cadet carburetor, I suggest taking it to your local lawn mower mechanic for assistance.

4. Cub Cadet Has a Broken Fuel Pump Fuel Filter 

A bad fuel pump is another reason that may have caused your Cub Cadet to stop while running. A fuel pump is used to pump gas to your carburetor. When the pump is broken or cracked, it fails to hold the pressure required to pump fuel.

FIX: Identify you have a faulty fuel pump by using your fuel shut-off valve or clamps to start and stop fuel flow as you test your fuel lines for fuel flow.

Once you have identified you are getting fuel to the pump, you will need to test the pump to see if fuel is being pumped out to your carburetor.

Do this by removing the fuel line from the carburetor and placing the line in a container. Start your lawn mower and watch the fuel line in a container to check for fuel being pumped out of your fuel pump.

You will want to see a steady or pulsating flow of fuel to know your fuel pump is operating as designed. Replace a fuel pump that has cracks in it or is no longer able to pump fuel to the carburetor.

5. Blocked Fuel Lines or Fuel Filter on Your Cub Cadet

Just like your carburetor can become clogged from running bad fuel, your fuel lines and fuel filter can also become plugged. Ethanol attracts moisture in the fuel system.

When that moisture evaporates, it leaves behind a gummy substance that runs through your fuel system and can cause blockages that restrict fuel supply causing your Cub Cadet to die after starting.

FIX: Replace a dirty fuel filter or a filter that isn’t allowing fuel to pass through. To clear a clogged fuel line, remove the fuel line, and spray carburetor cleaner into the line followed by compressed air to remove the blockage.

Once the clog is removed, reinstall it. The fuel line can easily be replaced with a new fuel line when the clog can’t be removed.

6. Bad Gas Cap on Your Cub Cadet

Something as simple as a gas cap can cause your Cub Cadet mower to die. Fuel caps are designed to vent. When the vent is blocked, a vacuum is created in the fuel tank which restricts the fuel flowing out of the tank. 

FIX: Remove your fuel cap and start your lawn mower, allow it to run. If your Cub Cadet no longer dies, this can be your problem. Be careful to not let any dirt or debris enter your fuel system when testing your mower without the fuel cap. 

Replace the fuel cap. If your lawn mower shuts off after running for a while, the fault can be with your fuel cap. You can try to see if you can clean the cap to allow it to vent. If you cannot, you need to replace the gas cap. 

7. Cub Cadet Has a Plugged Lawn Mower Air Filter  

Something as simple as a plugged air filter can cause your Cub Cadet to shut off. Your engine requires clean air to operate efficiently.

If your air filter is plugged with grass, dirt, and other debris, it can cause your engine to overheat because it is no longer able to get the air it requires.

Using a dirty air filter won’t only cause your mower to stop when running, but it can also cause extensive engine damage. Spending a little money to keep a clean air filter in your engine can save you a large engine repair or replacement bill down the road.

FIX: Remove the air filter from the air filter housing making sure not to knock any loose dirt into the air intake. If your air filter is a paper filter, knock the dirt out of the filter by tapping the filter against a solid surface.

Hold the air filter up to a light and make sure you see light through the filter. If you see light, that means air is still able to pass through the filter. You will need to replace the air filter if you are unable to see light through the paper filter.  

Your Cub Cadet lawn mower may use a different style of air filter. For cleaning procedures for other types of filters, read this article

8. Cub Cadet Has Dirty or Damaged Cooling Fins 

Cooling fins can get packed with dirt, grass, and oil. When the fins break or become packed with debris, the fins are not able to effectively dissipate heat around the engine block and cylinder head to keep your engine cool. 

FIX: Remove the engine cover and clean the cooling fins. Replace any damaged fins. Ensure the heat shield is attached correctly.

9. Dirty Spark Plug on a Cub Cadet Lawn Mower

A fouled spark plug can cause intermittent spark causing the mower to die. Remove the plug and inspect its condition.

FIX: Replace a spark plug that is very dark in color or is worn or damaged. If it is in good condition and only a little dirty, you can clean it with a small wire brush and reuse it.

When I’m having problems with a mower, I replace the spark plug to rule it out as the problem. A spark plug is an inexpensive part that affects the mower’s performance.

Ensure the spark plug is gapped correctly and the spark plug wire is securely attached. Either of these items can also cause the mower to quit running.

10. Bad Ignition Coil Causes a Cub Cadet Lawn Mower

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.

FIX: 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.

11. Too Much Oil or Too Little Oil in Your Cub Cadet  

Too much oil in your Cub Cadet lawn mower can cause your engine to smoke and die while mowing. The smoke can clog your air filter causing your engine to look elsewhere for air. 

Too much oil in your lawn mower can cause significant damage including internal engine damage and the possibility of having to replace your engine.  

Too little oil in your Cub Cadet mower will cause additional friction in the engine that can cause your engine to overheat and die. 

FIX: Perform your engine oil change according to Cub Cadet’s recommendations. Always fill oil to the correct oil fill levels.  

12. Plugged Mower Deck & Dull Blades 

A Cub Cadet mower deck that is packed with grass and dirt or a deck that is running dull blades can cause your engine to have to work harder.

Your blades may be hitting debris each time it turns putting a draw on your engine. This can make it overheat and shut down. 

FIX: Inspect your mower deck for any damage. Scrape the deck to remove debris and sharpen the blades. Always run your mower at full throttle when cutting grass. Avoid cutting wet grass. 

Your Cub Cadet Overheats or Smokes

While I have listed the most common problems your Cab Cadet may die while mowing, you may find more information on your issue if you have a starting or overheating problem. Refer to these articles on your Cub Cadet for more troubleshooting steps:

Reasons a Cub Cadet Mower Won’t Start: A Complete List

7 Things That Can Cause a Mower to Overheat

Why Your Cub Cadet Lawn Mower is Smoking

More Cub Cadet Problems & Solutions

As an owner of a lawn mower, you are guaranteed to run into problems over the life of the lawn mower. I have put together a list of the most common Cub Cadet problems & solutions to give you a guide when identifying the cause of your problem.

You never know when you’re going to run into more problems with your mower. Make sure you read and add this guide to your favorites: “Common Cub Cadet Mower Problems“.


Wednesday 14th of June 2023

Motor starts runs for 45 seconds and dies. I have replaced fuel filter, air filter, new battery, replaced all fuel lines, spark plug, fuel pump, changed oil and filter, cleaned engine and deck. Dirty carb ? better to replace or try to clean it?

Powered Equipment Team

Monday 19th of June 2023

It appears you believe you have a fuel issue and have replaced all fuel-related items to the carburetor. If you have verified you are getting good fuel flow to the carburetor, I would remove the air filter and spray a little carburetor cleaner (don't use starter fluid) into the air intake and see if the engine starts running better and then begins to sputter once the carburetor cleaner has burned off to narrow the fuel issue to the carburetor.

You can attempt to clean it to open the fuel passageways, but if it's pretty varnished and/or has damaged parts you're going to have to make the call on whether you want to take time to rebuild and clean it or if it's just easier to replace it. Price out the carburetor or rebuild kit and decide if it's worth your time.

One thing you didn't mention you checked that will cause a mower to shut down is the choke. The choke needs to be open once the engine warms to allow sufficient air to be drawn into the engine or the engine will shut down. Check the choke and make sure the plate is opening and closing correctly.

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