16 Reasons Your Kubota Mower Won’t Start: Solved!


You go out to start your Kubota lawn mower to perform your weekly yard care only to find it will not start. Developing problems with your lawn mower or any piece of equipment can be very frustrating, especially when you can’t find what is causing the problem. Starting problems in a mower can take some time to find because there are so many items that can prevent your it from starting.

A Kubota lawn mower may not start when it is unable to get the air, fuel and spark required to start. This can be a result of clogging or degradation of fuel system components, a plugged air filter, or a dirty spark plug. Faulty electrical parts including the safety switch, battery, ignition coil and battery can cause your mower not to start.

Keep reading for a complete list of items that can prevent your Kubota lawn mower from starting. I share steps to take when troubleshooting and repairing a starting problem.

Kubota lawn mower won't start

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Why Your Kubota Lawn Mower Will Not Start (The Complete List)

1. No Fuel in Your Kubota Fuel Tank 

The first thing you should do is check for fuel the fuel tank. I’m sure you already know this. I need to mention it just in case your overlooked the fuel tank in the heat of the moment.

Fix: Fill with fresh fuel. I write more about the correct fuel for your gas-powered lawn mower hereOpens in a new tab.

2. Bad or Old Fuel in Your Kubota

Kubota offers both gasoline and diesel powered lawn mowers. Fuel that is not fresh and has been sitting for a long period of time can become less effective and unstable. This means the fuel begins breaking down causing buildup in the fuel system that can cause running problems and clogging in the fuel system. This clogging can prevent your Kubota mower from starting.

If you are using a gas-powered Kubota mower, use an unleaded gasoline with a minimum octane rating of 87 and maximum ethanol level of 10 percent.  Ethanol, a corn-based fuel, is added to gasoline. This product is not good for small engines ran in Kubota mowers.

Avoid high contents of ethanol and use a fuel additive like Sea Foam Motor TreatmentOpens in a new tab. to stabilize your fuel reducing moisture buildup while cleaning the fuel system.

A diesel-powered Kubota obviously uses diesel fuel. Over time, diesel fuel that has been sitting for long periods of time will form solids and form condensation in the tank that can clog your fuel system. Old diesel fuel degrades and will have a dark appearance. Sea Foam Motor Treatment works well in diesel fuels to minimize moisture and stabilize it.

I recently took my diesel pickup truck to my mechanic for a service. He pulled the fuel filter and noticed it was black. He informed me I should no longer purchase fuel at the fuel station I visited every week. I was quite surprised by his findings since the fuel station is a very reputable station in the area. The bad diesel fuel result is most likely due to the dirty storage tanks at the station and it being stored for a long period of time.

Fix: Remove the old fuel using a fuel siphon. Drain the old fuel into an approved fuel container. Flush the tank and add fresh fuel with a fuel additive with cleaning agents. 

3. Bad Kubota Fuel Cap 

A bad Kubota fuel cap is one that doesn’t allow air to pass. Fuel caps are designed to vent. When it clogs and no longer vent, a vacuum is formed in the fuel tank not restricting fuel flow to the engine.

To determine whether the cap is your issue, run your mower with and without the cap. If your mower runs fine for a period of time without the cap, but eventually shuts off after a while once the cap has been reinstalled, you most likely have a problem in the fuel cap.

Fix: You can attempt cleaning your cap and try to remove the clog. If this does not work, replace with a new Kubota fuel capOpens in a new tab..

4. Kubota Mower has a Bad Spark Plug or Loose Connection 

A dirty spark plug is used on a gas-powered Kubota mower. Kubota diesel mowers do not use spark plugs. A spark plug can foul out causing your Kubota mower to not start. Remove your spark plug using a 3/4” or 5/8” socket depending on the model engine in your Kubota mower. Check it for signs of carbon build up, a broken porcelain or burnt filament.

You will also need to ensure your plugs are air gapped correctly according to your manufacturer specification. Once you reinstall or replace your spark plug, make sure the wire is securely connected so you can rule out spark plugs as the cause of your starting problem going forward.

Fix: Install a new spark plug when the spark plug is unable to be cleaned effectively, has a dark tip from buildup, has a burnt filament or has a damaged porcelain.

5. Kubota Air Filter is Plugged

A plugged filter restricts the amount of air your engine receives. A lack of air can prevent your Kubota mower from starting. Not only can a plugged filter cause your mower to fail to start, it can cause larger problems including extensive internal engine damage if it is not found and corrected right away.

It’s best practice to change your air filters annually when completing the full service on your Kubota mower. Periodically check and clean your air filters regularly through the mowing season. You may have to clean and replace your filters more often if you are operating your Kubota mower in dusty dry conditions.

Fix: Clean your paper filter element by removing it from the air filter housing. Be careful not to drop any dirt into the intake. Tap the filter against a solid surface to loosen and remove excess dirt. 

Hold the air filter up to the light to check to see if you can see light shine through your paper element. If you can, go ahead and reuse it. If you cannot, it’s time to replace it with a new filter.

For information on other types of air filters read my article hereOpens in a new tab.

6. Bad Kubota Fuel Pump 

A fuel pump is used on your Kubota mower to pump fuel from the fuel tank to the carburetor. The pump can become damaged or degrade the housing and components from old fuel sitting in the pump.

FIX: First, inspect your fuel pump for cracks, damage, or fuel leaking. If you notice any of these symptoms, replace your fuel pump. When no visible signs are present, you will need to take some steps to determine if your fuel pump is bad.

Confirm you have fuel flow to the pump

  • Turn off the fuel flow using the fuel shut-off valve located at the bottom of your fuel tank. You can also crimp your fuel line to stop flow.
  • Disconnect the fuel line from the inlet port on the fuel pump.
  • Place the fuel line in a container placed lower than the fuel tank. (Fuel will not flow if the line is higher than the tank because fuel will follow gravity.
  • Start your fuel flow and watch for fuel to flow into the container to confirm the fuel pump is receiving fuel. If you are not getting flow, your fuel restriction is prior to the pump. Check for a blocked fuel line or plugged fuel filter.
  • Reattach your fuel line to the fuel pump.

Test the fuel pump on your Kubota Mower

  • After verifying you have fuel flow to the pump, remove the fuel line from the carburetor and place it in a container.
  • Start your mower and watch fuel flow into your container.
  • If you have a pulsating or constant flow of fuel, your fuel pump should be fine. If you are not getting a consistent flow of fuel, replace your fuel pump.

7. Plugged Kubota Fuel Filter

Another fuel issue that can prevent your Kubota from getting the fuel it needs to start is a plugged fuel filter. Dirt and deposits from running old fuel can clog your fuel filter so fuel is no longer able to pass through the filter. 

Fix: Replace a plugged fuel filter with a new filter. Use the arrow on the plastic housing when installing your filter. The arrow needs to point in the direction of your fuel flow.

8. Blockage in the Fuel Line 

Old fuel that gummed up can become lodged in your Kubota mower’s fuel line preventing fuel from moving through your fuel system.

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 debris and gummy residue. You can also replace with new fuel line if you are unable to remove the clog or if your fuel lines are dry, brittle and beginning to crack.

9. Clogged & Dirty Kubota Carburetor 

The carburetor on your Kubota mower regulates the fuel and air mixture required to form a combustion in the engine. The carburetor can gum up and clog so it no longer can function correctly.

Fix: Clean the carburetor by taking it apart and using carb cleaner to clean the carburetor including the float bowl and needle. You can find steps for cleaning your carburetor in this articleOpens in a new tab.

10. Kubota Has a Bad Battery or Loose Terminals 

Your Kubota lawn mower won’t start when the battery is dead. Make sure your battery cables are secure and the connections are not showing signs of corrosion. 

Fix: Test your battery with a multimeterOpens in a new tab.. You will want a reading of about 12.7 volts. Place on a charger to charge your battery if your reading is less than 12.7 volts. Read more about the steps and items needed to charge your battery here. If your battery does not hold a charge, you will need to replace it with a new battery. 

11. Bad Kubota Safety Switch

Your lawn mower may use several safety switches in its operator’s presence control system. The switches are designed to kill the engine if the operator leaves the seat. Refer to your operator’s manual for the location and function of all safety switches on your Kubota model. A bad switch can cause your Kubota mower not to start. 

Fix: You can temporarily bypass the safety switch to identify a bad switch. A multimeter can also be used to help identify a bad switch. Never operate a mower without a good safety switch or when the switch is bypassed. 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.

12. Kubota Has a Bad Ignition Switch 

You insert the key into your ignition switch and turn it only to find nothing happens. Your Kubota mower won’t start. The ignition switch can be the culprit.  Check the switch with a multimeter.

Fix: Replace the Kubota ignition switch if you find it is bad

13. Bad Ignition Coil on Your Kubota Mower

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 a ohm meter. Replace the ignition coil if you find a break in the continuity. 

14. Bad Starter Solenoid on Your Kubota Mower

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

Fix: Test your Kubota mower solenoid by following the steps here. Replace your solenoid if it is found to be bad.

15. Kubota Mower’s Charging System is Not Charging 

The charging system can drain the battery and cause your lawn mower not to start. A bad stator or alternator can be the problem among other things. I show steps on how to test your charging system hereOpens in a new tab. using an ohm meter. 

Fix: If you find the problem is in your charging system, have a small engine mechanic identify the actual cause of the failure. It could be several different items and you don’t want to start guessing at the cause of the problem. Throwing parts at your Kubota mower gets very pricey. 

16. Incorrect Operating Procedure When Starting Your Kubota 

There are different safety procedures taken by Kubota when starting and operating your lawn mower that will shut off the mower. For example, when you get off your zero turn mower with the engine still running, your mower will shut off if you fail to set the parking brake first.   

Fix: Refer to your Kubota 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. 

Powered Equipment Team

We're just a guy and a girl obsessed with outdoor power equipment! We are excited to share the knowledge and tips we have learned over our combined 55 years in the power equipment industry. We have both ran equipment dealerships and took pleasure in helping our customers everyday providing equipment repair, parts, purchasing, and business tips to our residential and commercial clients. We hope our blog will help you with your next purchase, repair, or project.

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