It’s that time of the week again when you need to cut your lawn, but this time your Cub Cadet mower will not start. Over my years of consulting with homeowners and commercial customers, I have troubleshot a lot of starting issues. You can find the most common causes here.

There are many reasons why a Cub Cadet lawn mower won’t start including a loose spark plug connection, plugged air filter, bad fuel pump, bad battery, corrosion on the electrical components, dirty carburetor, bad switches, or a faulty charging system. 

As frustrating as it is to have a mower that won’t start, I’m going to take you through a list of reasons why your Cub Cadet may not be starting. Hopefully, the starting problem is a simple fix, and you can get back to mowing your lawn. Let’s find out! 

Cub Cadet mower won't start

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Follow all safety instructions provided in your equipment operator’s manual prior to 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.

16 Reasons Your Cut Cadet Mower Won’t Start (Causes & Solutions)

1. No Gas in Your Cub Cadet Fuel Tank Causes the Mower Not to Start

You may be wondering why something as simple as gas in a fuel tank shows up on the list. Gas is an obvious reason why your Cub Cadet won’t start.

As obvious as it seems, you may be surprised to learn of the number of complaints I’ve received from customers about their starting problem when the culprit was no fuel in the lawn mower. 

Fix: Fill and empty the tank with fresh unleaded gasoline with an octane rating of 87-grade or higher. Choose a gas with an ethanol level no greater than 10%. Find more information on the correct fuel for your gas Cub Cadet lawn mower here. 

2. Bad or Old Fuel  in Your Cub Cadet Lawn Mower Causes a Starting Problem

Gas begins to deteriorate, break down, and become less effective after about 30 days. The ethanol used in gasoline attracts moisture.

This moisture, once it evaporates, leaves a gummy residue behind that can clog your fuel system including your fuel lines, filter, and carburetor. 

It is necessary to purchase fuel from a busy gas station and use it within a 30-day time period. If you are unable to consume the fuel within this time, you need to add a fuel additive to stabilize the fuel so it lasts a little longer without breaking down.

Fix: Remove the old fuel from the fuel tank using a fuel siphon pump. Add fresh fuel along with a fuel additive to clean and remove moisture from the fuel system. I prefer to use the product Sea Foam Motor Treatment.

3. Faulty Cub Cadet Fuel Cap Causes a Mower Not to Start

Your fuel cap has a vent. When this vent gets plugged, your fuel tank will create a vacuum preventing your Cub Cadet mower from drawing gas out of the fuel tank. 

To check whether your gas cap is the cause of your starting problem, remove the cap and start your mower. If the Cub Cadet that wouldn’t start now starts, go ahead and reinstall the cap with the lawn mower still running.

What you’re waiting for now is for the mower to sputter and die from a lack of fuel. If it does, remove the cap and see if the mower will start up again.

You have a problem with the fuel cap when you experience this kind of starting and dying from a fuel cap that is removed and installed on your Cub Cadet.

Fix: Replace with a new fuel cap. You can find one on Amazon or visit your local Cub Cadet dealership. 

4. Cub Cadet Has a Bad Spark Plug or Loose Connection 

Another reason your Cub Cadet won’t run may be due to a bad spark plug connection or a damaged spark plug. A plug that has carbon buildup or oil on the tip can foul out causing your engine to misfire and not start.

Check the spark plug wire to ensure it’s making a good connection. Your spark plug must be gapped to the engine manufacturer’s specification.

You can experience starting and running problems with a loose spark plug wire or an incorrectly gapped spark plug.  

Fix: Remove your spark plug and inspect it for signs of carbon buildup or cracked porcelain insulator. Replace with a new spark plug(s). Make sure the spark plug is gapped correctly using a feeler gauge.

5. Plugged Cub Cadet Air Filter Causes Mower Not to Start

The engine in your Cub Cadet requires air to run. If your air filter gets extremely dirty, it can starve the engine of air because air will no longer be able to pass through the filter. A Cub Cadet engine that doesn’t get sufficient air will not start.

When the airflow is blocked by your air filter the engine must find air to continue to run. It may begin to overheat and draw what air it can find from the crankcase which can cause extensive damage to the engine.

Fix: Clean a paper air filter by removing it from the air filter housing. Take caution when removing it to ensure you are not dropping any loose dirt into the air intake. You will need to wipe out any remaining dirt in the housing with a clean dry cloth.

Knock the excess dirt out of the filter by tapping it against a hard surface. Do not use an air compressor to clean the air filter. Once you have gotten as much dirt out of the filter as possible, hold it up to the light to see if you are able to see light shine through the paper.

If you can see light and it is not damaged or covered in oil, you can reuse the filter. If you cannot see light, you must replace the filter.

You can find information on other types of air filters and how to clean them here. 

6. Bad Cub Cadet Fuel Pump Causes It Not to Start

The fuel pump exists to get fuel to the carburetor. When the fuel tank sits below the carburetor a pump is needed to help move the gas.

A fuel pump, just like any other mechanical part, can fail over time. A likely cause is due to old fuel deteriorating the pump components.

Fix: To identify a failing fuel pump, first, inspect your vacuum fuel pump for cracks. If you see fuel outside of the fuel pump or cracks in the pump, the pump will no longer be able to use the pressure off the crankcase to push fuel to the carburetor. 

Using the fuel shut-off valve, if your mower has a valve, or clamps to stop and start fuel flow will help you control fuel flow. Stop and start flow to make sure you are getting fuel to the pump. If you are not getting good flow to the pump, check the fuel line or fuel filter for restrictions.

Once you verify your pump is getting fuel, check to make sure that fuel is being pumped out of the pump in a steady or pulsating flow to identify whether or not your fuel pump is bad.

Do this by stopping your fuel flow and removing the fuel line from the carburetor. Place the line in a container. Start your fuel flow and your mower.

Watch the flow of fuel into the container. If you have a good consistent or pulsating flow of fuel, your fuel pump is okay. If not, replace the fuel pump.

7. Clogged Fuel Filter Causes a Cub Cadet Not to Start

Your fuel filter is a line of defense to prevent dirt and debris into the engine by straining the fuel. Make sure the fuel that is running into the filter is also running out of the filter.

If it does not, you must replace it because it is most likely plugged preventing your Cub Cadet from starting.

Fix: Replace the fuel filter if you have found your fuel flow stops at the fuel filter. Install a new fuel filter on your Cub Cadet if needed. The filter must be installed so the arrow on the filter is pointed in the direction of the fuel flow.

8. Clogged Fuel Line Causes a Cub Cadet Not to Start

Old fuel and dirt leave deposits that can clog your Cub Cadet mower’s fuel line.  

Fix: Remove the fuel line, spray carb cleaner into the tube and use compressed air to blow air through the tube until the line is free of dirt and gummy residue. You can also replace it with a new fuel line. 

9. Clogged & Dirty Carburetor Causes a Cub Cadet Not to Start

The function of the carburetor is to regulate the right amount of gas with the right amount of air so your engine can create a combustion. Carburetors can get crusty buildup and gummy deposits from using old fuel containing ethanol.

When the carburetor is no longer to regulate the fuel your engine receives, your Cub Cadet engine will run rough or it may not even start at all.

Fix: If you are somewhat mechanical, you can try to clean the carburetor yourself, otherwise, bring it to your lawn mower repair shop. You can find steps for cleaning your Cub Cadet carburetor in this article. 

You may choose to replace the carburetor if it appears to be in very bad condition. 

10. Bad Battery or Loose Terminals on Your Cub Cadet Causes It Not to Start

Your Cub Cadet lawn mower requires a charged battery in order to start. If your cables happen to be loose or your battery terminals show signs of corrosion, they can cause your mower starting problems.

Fix: Test your battery with a multimeter. You need a reading of about 12.7 volts. Charge your battery if it is lower than this level. You can find more information on charging your battery here.

If your battery does not hold a charge, you will need to replace it with a new battery. 

11. Bad Safety Switch on Your Cub Cadet Causes It Not to Start

Your lawn mower may use several safety switches in its operator’s presence control system. The switches are designed to kill the engine when the operator leaves the seat.

A faulty switch may not recognize when the operator is in or out of the seat causing your mower not to start. 

Fix: You can temporarily bypass the safety switch to identify a bad switch. Do not operate a mower without the safety switch installed for your safety. 

Many people get injured by mowers annually by rolling them or falling off the mower.  Always have safety switches installed and working on your equipment. Replace a bad switch. 

12. Bad Cub Cadet Ignition Switch Prevents Mower from Starting

You insert the key into your ignition switch and turn it only to find nothing happens. Your Cub Cadet mower does not start. The ignition switch can be the culprit. You can use a multimeter to test the ignition switch 

Fix: Replace the switch if bad 

13. Bad Cub Cadet Ignition Coil Causes the Mower Not to Start

The ignition coil provides voltage to the spark plug so it can fire and start the engine. The engine will not start if the spark plug isn’t able to fire.  

Fix: After you verified your spark plug is in good condition, check the continuity of your ignition coil using an ohm meter. Replace the ignition coil if you find a break in the continuity. 

14. Bad Starter Solenoid on Your Cub Cadet Causes Mower Not to Start

A lawn mower solenoid is an electromagnetic switch that is like an on-off switch that actuates the starter motor to turn over the engine. A click or hum when turning your ignition key is an indication to check your solenoid.

Another indication your Cub Cadet mower solenoid may be bad is when a wire attached to your solenoid gets hot and begins to smoke or melt.

FIX: Test your Cub Cadet mower solenoid by following the steps here. Replace your solenoid if it is found to be bad.

15. Cub Cadet Mower’s Charging System is Faulty

While the charging system isn’t the main reason a Cub Cadet mower won’t start, it can contribute to a weak battery that prevents the mower from starting.

When the charging system fails to charge the battery, the battery may not be able to start the mower the next time you go to use it.

A bad stator or alternator can be the problem along with several other electrical parts. Read this article to test your charging system here using an ohm meter. 

Fix: If you believe the problem to be in your charging system, I suggest you allow a small engine mechanic to identify which part of the charging system is your problem. Taking a guess at the problem and throwing parts at your mower can get pretty expensive.

16. Incorrect Operating Procedure to Start Your Cub Cadet Mower

Cub Cadet has safety features that won’t allow your mower to start unless you follow their starting procedures.

Fix: Refer to your Cub Cadet operating manual to ensure you are operating your lawn mower correctly, so you don’t set off the safety features that shut off your lawn mower or don’t allow it to start.

Cub Cadet Starting Problems & Solutions (Quick Reference Chart)

Empty Fuel TankFill with fresh fuel. Cub Cadet mowers with 4-cycle engines require a minimum 87-octane rating and maximum 10% ethanol content.
Bad or Old GasolineDrain the old fuel. Fill with fresh fuel adding a fuel stabilizer that reduces moisture and cleans the fuel system.
Plugged Air FilterClean the filter by knocking dirt out of a paper air filter. If the filter is very dirty, dark in color, wet or damaged, you should replace it with a new filter.
Dirty or Damaged Spark PlugClean a dirty spark plug with a wire brush. Replace the plug with a new one if it is very dirty, has broken porcelain, or damaged electrode.
Plugged Fuel FilterReplace a plugged fuel filter with a new filter. Make sure the arrow on the inline filter is installed and pointed in the direction of the fuel flow.
Plugged Fuel Line Shut off the fuel supply and remove the fuel line from the mower. Use carburetor cleaner to loosen the clog and compressed air to remove it. Replace a line if you are unable to remove the restriction.
Bad Fuel PumpCheck fuel flow from the pump. Replace a bad fuel pump.
Dirty CarburetorRemove the carburetor and clean it with a carburetor cleaner. You may need to rebuild it or replace it if cleaning alone does not work.
Bad Safety SwitchReplace a bad safety switch.
Bad Battery or Bad ConnectionsTest the battery. Make sure the wires and cables are making a good connection. Remove any corrosion on the terminals and wires.
Faulty Ignition SwitchReplace a bad ignition switch.
Plugged or Faulty Fuel CapReplace a fuel cap that is no longer venting and allowing air to pass through the tank.
Bad Ignition CoilReplace a bad ignition coil if there is a break in continuity.
Bad Starter SolenoidTest a Cub Cadet starter solenoid and replace it if bad.
Faulty Charging SystemIf the battery is good and will hold a charge, but the mower continually dies due to a dead battery and will not start, have a mechanic identify whether your problem lies with a component of the charging system.
Incorrect Starting ProcedureFollow starting procedures for the mower as there are safety switches that can prevent the mower from starting if not following the correct steps.

Still Having Problems with Your Cub Cadet Mower?

If these tips haven’t solved your Cub Cadet problem or if you are experiencing a different problem with your Cub Cadet, check out my guide showing the most common Cub Cadet problems and their solutions: Common Cub Cadet Problems.

Here you’ll find the causes of Cub Cadet issues like the mower not starting, a bad cut, a vibration, or a smoking problem. I include solutions along with links to more in-depth information.

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