You love your zero-turn. It’s a fast and efficient way to mow a sizable lawn. However, just like any other piece of equipment, there will be times when it won’t start when you need it.
A Bobcat zero turn won’t start when it isn’t getting sufficient air, fuel, and spark due to a plugged air filter, clogged fuel line, bad fuel pump, dirty carburetor, bad spark plug, faulty ignition coil, bad battery, faulty switch or loose connections.
Keep reading for additional causes of a Bobcat starting problem. Take all safety precautions when performing repairs including removing the spark plug wire.
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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.
Troubleshoot a Bobcat Zero Turn Mower Starting Problem
- Check for a lack of fuel
- Empty fuel tank
- Old fuel
- Plugged fuel filter
- Clogged fuel line
- Bad fuel pump
- Dirty carburetor
- Make sure you are getting spark
- Damaged or dirty spark plug
- Check for a lack of air
- Plugged air filter
- Incorrect choke setting or stuck choke
- Incorrect starting procedure
- Check the electrical system
- Bad or weak battery
- Loose cables, wiring, and connections
- Faulty safety switch
- Bad ignition switch
Reasons Your Bobcat Zero Turn Won’t Start
Empty Fuel Tank
I only mention an empty fuel tank because some people forget to check this obvious reason for a lawn mower not starting.
You may have developed a fuel leak and haven’t realized you are going through more fuel than normal. You may have simply forgotten the last time you bought fuel or the fuel gauge is faulty.
SOLUTION: Check the fuel tank to make sure you have a sufficient amount of fuel required to start and run the mower. Check for a fuel leak or faulty gauge and repair as necessary.
Add fresh fuel to a fuel tank that is at a low level or empty.
Old Fuel
Gas for a Bobcat Lawn Mower
Old fuel can have a negative effect on your Bobcat zero turn. Gas will begin to break down and become less effective as quickly as 30 days after purchase. This can result in problems that can keep a mower from starting.
Most gas contains an alternative plant-based fuel, often made of corn, called ethanol. While adding ethanol makes gasoline more environmentally friendly, it is not good for the small engine used on your Bobcat lawn mower.
Ethanol naturally attracts moisture out of the air that can cause premature corrosion in the mower and leave behind sticky deposits that restrict fuel flow.
Use Gas with a Low Ethanol Content or Ethanol-Free Fuel
Bobcat lawn mowers require an unleaded gas with a minimum octane rating of 87 and a maximum ethanol content of 10%.
Do not use gas with ethanol levels higher than this like those sold as E15 and E85 gas. These contain ethanol levels up to 15% and 85% respectively.
Ethanol-free fuel is the best type of fuel to use in your Bobcat mower because you don’t have to deal with the negative ethanol effects, but it is a little pricey.
Use Fresh Fuel in a Bobcat Mower
Because of how quickly gas can start to go bad, purchase an amount of fuel that you can consume within 30 days.
If you are unable to use it within 30 days, add a fuel additive like Sea Foam Motor Treatment to your fuel to stabilize it so it lasts a little longer without breaking down. This product must be added to fresh fuel. It cannot reverse the effects of old fuel.
SOLUTION: When you find old fuel in your Bobcat mower, drain the fuel tank using a fuel siphon pump. Mix your fresh gas with Sea Foam or STA-BIL to stabilize the gas and reduce moisture in the fuel system.
Read more about why I choose to use Sea Foam in every tank of gas in “Use Sea Foam Additive in a Lawn Mower to Stabilizer Your Fuel“.
Bad Gas Cap
The gas cap on a Bobcat mower is designed to vent to allow air to pass through the cap. When a fuel cap vent is plugged or damaged, the fuel tank forms a vacuum starving the engine of gas.
A Bobcat mower won’t start when it isn’t getting gas. You may be able to identify a bad gas cap that is no longer venting when the mower doesn’t start until you loosen or remove the fuel cap to allow air into the fuel tank.
If it starts after loosening the cap, tighten the cap and allow the mower to continue to run for some time to see if you can replicate the issue.
You want to see if the mower will shut off and not start again until you loosen the fuel cap.
SOLUTION: When the gas cap is not venting, replace it with a new Bobcat fuel cap.
Bad Spark Plug
A fouled or damaged spark plug can cause intermittent spark problems causing your Bobcat to fail to start. An incorrect electrode gap or loose spark plug wires can also contribute to the problem.
SOLUTION: Remove the spark plugs using a socket wrench. Look for wear and damage including cracked porcelain, burnt electrode, and a dirty plug.
A damaged or excessively dirty plug that is dark in color must be replaced with a new spark plug. If the plug is just a little dirty, you can clean it with a wire brush.
Before installing the clean or new plugs, make sure they are gapped to the engine manufacturer’s specifications. Install the spark plug and securely attach the spark plug wire to ensure it is making a good connection.
Plugged Air Filter
Operating a Bobcat zero turn stirs up a lot of dust and debris. That is why it’s important to always run an air filter to avoid engine damage.
This dirt can plug the air filter restricting the amount of air getting to the engine. A lack of air will prevent your mower from starting.
Running a plugged filter can cause the mower to overheat potentially causing additional engine damage. Never run your Bobcat mower without an air filter, even if it’s only for a short period of time while you finish your mowing task.
SOLUTION: I recommend starting each mowing season with a new air filter. The air filter maintenance doesn’t stop here. You must check and clean it several times throughout the mowing season.
The dustier the mowing conditions, the more often you need to check and clean your air filter.
Clean a Bobcat mower paper air filter:
- Remove your filter from the air filter housing.
- Wipe out any dirt remaining in the housing with a dry clean rag. Don’t allow dirt to fall into the air intake.
- Tap your air filter against a solid surface. Knock as much dirt out of the filter as you can get loose. Don’t use compressed air to clean your filter as this will damage a filter.
- Check for light shining through the paper filter element by holding it up to a light source.
- If you can see light through the paper, reuse the air filter. If you can’t see light, the filter is covered in oil, extremely dirty, or damaged, replace the filter with a new one.
- Install your air filter in the housing and reattach the air filter housing cover.
Plugged Fuel Filter
A fuel filter is used to strain fuel coming out of the fuel tank to remove dirt and other contaminants from the fuel. The filter can become clogged if you haven’t changed the fuel filter regularly or are running dirty gas.
A plugged fuel filter will prevent a steady flow of fuel from passing through the filter keeping your mower from starting. It is good practice to replace the fuel filter annually.
SOLUTION: A clogged fuel filter must be replaced with a new one. When installing a new inline fuel filter on your zero turn, make sure the arrow on the side of the filter is pointed in the direction of the fuel flow.
Clogged Fuel Line
Bad or old fuel can cause clogging and damage throughout your fuel system. This includes the fuel lines as well.
To check for a clogged fuel line, use the fuel shut-off valve or fuel pinch pliers to crimp the line to stop the flow of fuel coming out of the fuel tank.
With your fuel flow stopped, remove one end of a section of the fuel hose (the end furthest from the fuel tank) and place it into a container. Make sure the container is placed lower than the fuel tank.
Fuel cannot flow uphill without the assistance of the fuel pump. Start your fuel flow and check the fuel coming out of the hose you placed in the container. If the flow looks good, reattach the fuel line.
SOLUTION: If you find a clogged line, you must remove the blockage. Do this by stopping the fuel flow and removing the fuel line from your mower. Spray carburetor cleaner into the line to help loosen the blockage.
Follow this with compressed air to blow air into the line to remove the blockage. Repeat this process until the clog is removed. If you are unable to dislodge the clog, you will need to replace your fuel line.
Bad Fuel Pump
A fuel pump can fail over time. Old gas sitting in your fuel pump can degrade it causing it to fail.
The fuel pump will no longer be able to use the engine vacuum to draw fuel from the fuel tank and move it to the carburetor causing your Bobcat mower not to start.
Check for leaks on your fuel pump. If you don’t find a leak, you will need to perform a couple of tests to make sure your fuel pump is operating properly. Before you do this, verify you are getting fuel to the pump.
Once you have verified you are getting flow to the inlet port on the pump, check the flow of fuel being pumped out of the fuel pump.
Do this by disconnecting the fuel hose from the carburetor and placing it in a container. Start your mower and watch the hose for a constant or pulsating fuel flow.
SOLUTION: Replace your fuel pump if you are not receiving a constant or pulsating flow out of the pump.
Dirty Carburetor
Old fuel running through your Bobcat mower can cause the carburetor to fail to function properly because deposits are left behind that clog the fuel jet and gum up the small components that make up the carburetor
The carburetor’s purpose is to regulate the amount of gas mixed with air to create combustion in the engine.
When the carburetor isn’t able to function correctly, it will affect the mower’s ability to start and run. It must be disassembled and cleaned to remove gummy and crusty buildups.
SOLUTION: If you are a little mechanical you should be able to handle disassembling the small parts in a Bobcat carburetor. Just follow the steps in this article to clean the carburetor.
However, if you don’t want to tackle cleaning the carburetor, you can replace it with a new one or have a local small engine mechanic clean the carburetor and reinstall it.
When you find the carburetor is too dirty to clean adequately, you should replace it. Locate the model and spec number of the engine and contact your local Bobcat dealership.
You can also call the engine dealership. For example, if you’re running a Bobcat with a Kawasaki engine, you can contact a Kawasaki engine dealer for parts.
Bad Battery, Loose Cables, or Corroded Terminals
A bad battery or one that won’t hold a charge will keep your Bobcat zero turn from starting. Loose battery cables, loose wiring, and corroded terminals can also contribute to this problem.
Confirm your battery terminals are not corroded and are attached securely to the battery.
SOLUTION: Clean corroded terminals in a baking soda solution containing 2 cups of water and 3 rounded tablespoons of baking soda. Use a wire brush to scrub the terminals clean.
Test your battery with a multimeter. You will want a reading at about 12.7 volts. Charge the battery with a battery charger if you get a reading lower than this.
Read more about the steps and items needed to charge your battery here. When the battery won’t hold a charge, replace it with a new one.
Faulty Safety Switch
Bobcat installs safety switches to prevent the mower from starting when certain events are not met.
It also has a safety switch that disengages your mower deck and shuts off your mower if it no longer senses the operator is present.
When one of the safety switches fails, a mower may fail to start.
SOLUTION: Refer to the operator’s manual to ensure you follow the correct starting procedures so a safety switch isn’t preventing the mower from starting.
If you are following the starting steps correctly and it still doesn’t start, test the safety switches using a multimeter. You can temporarily bypass the safety switch to identify a bad switch but only do this for troubleshooting purposes.
Never operate a mower without the safety switch. Never run a mower when a safety switch is bypassed. A safety switch can save you from serious injury and you never know when you’re going to need it.
Bad Ignition Switch
You insert the key into your ignition switch and turn it only to find your Bobcat doesn’t start or even turn over. The ignition switch could be the problem.
SOLUTION: You can use a multimeter to test the ignition switch. Replace the switch if bad.
Faulty Charging System
While the charging system isn’t the primary reason causing your Bobcat lawn mower not to start, it can contribute to a weak battery. The charging system is important to keep your battery charged.
If you find your battery keeps dying and you have to keep placing it on a charger, you may have problems with the charging system.
When a component of this system fails, your Bobcat mower will not start because the battery will not provide enough power. The bad charging system will fail to charge the battery so it may not start the next time you go to use the mower.
A bad stator or alternator can be a problem. I show steps on how to test your charging system here using an ohmmeter.
SOLUTION: Have an experienced mechanic at your local Bobcat mower dealership or small engine repair shop check the charging system to isolate the problem.
You can attempt to try to solve the problem yourself, however, if don’t have experience with charging systems, you will most likely just be replacing electrical items until you find one that fixes the problem.
This can get very expensive because most parts stores won’t let you return electrical parts if you find a part your purchased doesn’t resolve your starting problem.
Incorrect Operating Procedure
In order to start a mower with a cold engine, the choke must be engaged to restrict airflow to the engine. This is to allow a higher concentration of gas and less air needed to form combustion in a cold engine.
After the mower starts and the engine warms up, the choke lever needs to be adjusted to the off position to allow sufficient air to be mixed with the fuel so the mower continues to run.
SOLUTION: Always make sure you use the choke to start a cold engine and then adjust it to the off position once the engine warms. Check the choke linkages when you find the choke lever isn’t working correctly.