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14 Reasons a Bobcat Zero Turn Starts Then Dies

A Bobcat zero-turn mower starts then dies due to a clogged air filter, dirty spark plug, faulty ignition coil, clogged fuel line, plugged fuel filter, bad fuel pump, dirty carburetor, or old fuel.

It may also stop running when the engine oil is low or high, the cooling system is plugged, or the mower deck is clogged.

Keep reading and I’ll share a list of items that contribute to your running problem. Follow safety precautions including removing the spark plug wires before performing repairs.

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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.

Your Bobcat Zero Turn Starts Then Dies (Keeps Shutting Down)

1. Bad or Old Fuel

Fuel that has been sitting in your mower for a while can begin to break down and become less effective. Most gasoline sold today contains ethanol, a corn-based product.

This product attracts moisture from the air and is corrosive to the fuel system. When this solution evaporates, it leaves behind varnish that can result in fuel restrictions.

Clogged fuel components prevent your zero-turn from getting the fuel it needs to continue to run. Not only will this solution clog the fuel system, but over time it will separate from the gasoline and sink to the bottom of the fuel tank.

Tips for selecting and storing gas for your Bobcat mower:

  • Purchase and consume fresh fuel within 30 days.
  • Use unleaded gas with a minimum 87-octane rating and minimum 10% ethanol content.
  • Stay away from gas with high ethanol contents line E15 and E85 fuels.
  • Store fuel in a dry location away from combustible products.
  • Mix fresh gas with a fuel additive to keep fuel stable.

SOLUTION: Drain old gas into an approved fuel container. A fuel siphon pump works well for this.

Mix fresh gas with a fuel additive like Sea Foam Motor Treatment. This is to help clean the fuel system and reduce moisture. It also keeps the fuel stable longer.

Add the fuel mixture to the fuel tank. Start and allow the engine to run so the treated fuel works its way through the system.

Read more about the positive effects of Sea Foam here.

2. Clogged Fuel Filter

A fuel filter is used to keep dirt from entering the fuel system and wearing on fuel components and the engine. This filter must be regularly replaced to ensure a good flow of fuel can pass through it.

When the fuel filter becomes plugged with dirt your engine will die from the lack of fuel.

SOLUTION: Replace a plugged fuel filter with a new one. Check the side of the air filter for an arrow printed on the filter housing.

If your filter includes one, the filter must be installed with the arrow pointed in the direction of the fuel flow.

3. Clogged Fuel Lines

A gummy substance from running old fuel can run through the fuel system and create a blockage in the fuel line. This can cause your Bobcat mower to die after it has been running for a while because the engine is no longer getting fuel.

Check for blockages in your fuel lines using the fuel shut-off valve to start and stop fuel flow while checking each section of the fuel line for fuel flow.

SOLUTION: If you find a fuel line that has a blockage, turn off the fuel supply and remove the fuel line from the mower.

Spray carburetor cleaner into the fuel line. This is to loosen up the clog. Follow this by blowing compressed air through the line to remove the blockage.

If you are unable to dislodge the blockage to open the fuel line, install a new fuel line on your mower and turn on your fuel supply.

4. Faulty Fuel Pump

Most fuel pumps used on zero-turn mowers are vacuum pumps. They build pressure off the engine block and pump fuel to the carburetor. Pumps can fail mechanically or from the degradation caused by old gas.

To determine you have a bad fuel pump, confirm you are getting fuel flow to the fuel pump by checking flow through the fuel line. You may have done this in the prior step.

Next, check the fuel flow out from the fuel pump. Turn off your fuel flow and remove the fuel line from the carburetor. With the line placed in a container, turn on your fuel flow and start your Bobcat zero-turn.

SOLUTION: Watch for a steady or pulsating flow of fuel out of the line indicating your pump is working. If you don’t get a good flow, replace the fuel pump.

5. Dirty Carburetor

The carburetor regulates the amount of gas and air allowed into the combustion chamber to form combustion.

The components on your carburetor can become clogged and fail to release the amount of fuel your engine needs to run causing it to run sluggishly or die.

Before you disassemble and clean your carburetor perform these simple checks to determine the problem is in your carburetor:

  • Confirm you have fuel flow to the carburetor. You should have verified this if you check the fuel flow out of your fuel pump.
  • Remove your air filter from the air filter housing.
  • Spray carburetor cleaner into the air intake and start your mower.
  • If the zero turn starts, runs fine, and then shuts down, your problem may be in the carburetor.

SOLUTION: Remove the carburetor from your zero-turn. Disassemble it and clean the carburetor. Refer to this article for carburetor cleaning steps.

Bring your mower to your Bobcat servicing dealer or a small engine repair shop if you choose to have someone else tackle this job for you.

6. Plugged Air Filter

One of the requirements for your engine to run is air. If your zero-turn died while mowing, it can be the result of a plugged air filter. When it becomes plugged, air can no longer pass through the filter and to the engine.

You should replace your air filter once a year and check it several times during the mowing season to keep it clean.

You’ll need to clean it more frequently when you are operating the mower in dusty conditions.

SOLUTION: Follow these instructions to clean your paper air filter:

Clean a Bobcat mower PAPER air filter:

  • Remove your paper air filter element from the housing.
  • Wipe out any dirt remaining in the housing with a clean dry cloth. Don’t allow dirt to fall into the air intake.
  • Tap it against a hard surface to remove as much dirt as you can get to fall out of the filter. Don’t use compressed air as this will damage the paper.
  • Hold your filter up to a light source. Replace your filter with a new one if the light is not shining through the paper element, it is damaged or covered in oil. If it is, go ahead and reuse it.
  • Install your air filter and reattach the filter housing cover.

7. Plugged Engine Cooling System

The engine can overheat when the cooling system isn’t kept clean allowing air to properly circulate around the engine block and cylinder head.


Clean the cooling system:

  • Remove any dirt you find on your cooling fins and replace any broken fins.
  • Remove dirt from around the engine block and from the engine shroud.
  • Make sure your heat shield is correctly installed to help with air circulation.

8. Low Engine Oil Level

It’s important to check the engine oil level in your zero-turn before each use. Many mower owners skip this step. Checking the engine oil level using the oil dipstick is a fairly quick process.

Catching a low engine level before it causes engine damage to your Bobcat mower can save you from a costly repair expense. Running your zero-turn with a low engine level can cause your mower to overheat and shut down.

When there isn’t enough engine oil to lubricate the internal engine components, friction among the parts will build creating heat in the crankcase. This excessive heat can begin burning oil and parts in your engine.

SOLUTION: When you run into a problem with your mower shutting down due to a low engine oil level, you can attempt to add more oil to correct the level and start your mower.

Most of the time, if your mower shut down because of a lack of lubrication, the simple fix of adding more engine oil isn’t going to work.

Most likely, significant engine damage was caused. It is best to have an experienced small engine mechanic take a look at your mower to find out how much damage occurred.

9. Too Much Engine Oil

Not only can low engine oil cause your engine to die, but also too much engine oil can make your zero-turn shut down. Excess oil will cause pressure to build in the crankcase. Read more about the effects of running too much oil here.

SOLUTION: If you find, after checking your engine oil, that your level is too high, remove a little bit of oil.

Oil can be removed out of the drain plug, oil filter, or out of the oil fill area using an oil evacuator or turkey baster. Continue to remove and add engine oil until the level is corrected.

10. Dirty Spark Plug or Loose Connections

A fouled spark plug can cause your zero-turn to die. Check your Bobcat mower for a spark plug that is dirty or isn’t correctly gapped. Loose spark plug wires can also cause your mower runs sluggish or dies.

SOLUTION: Remove the spark plug and clean the spark plug if it is dirty. If it happens to be very dark in color or damaged, install a new spark plug.

Make sure it is correctly gapped according to your engine manufacturer’s specification and the spark plug wires are securely attached.

11. Bad Ignition Coil

The winding on the ignition coil can separate and short out when your mower is hot. When this happens, the spark plugs are unable to get the voltage they need to create a spark.

This can cause your Bobcat mower to die after it’s been running for a while.

SOLUTION: Identify a bad ignition coil using an ohm meter to check for a break in continuity. Replace the ignition coil if you find there is a break.

12. Choke is in the Wrong Position

Your zero turn has a choke to allow more fuel to be allowed into the combustion chamber by restricting airflow. This is needed to start your engine when it is cold.

If you leave your choke on after your engine heats up, your zero-turn will die.

SOLUTION: Make sure your choke lever is in the right position. If you continue to have airflow problems and have confirmed the choke lever position is correct and you have a clean air filter installed, check for a stuck choke plate.

The plate must open and close when the choke lever is moved. Use carburetor cleaner to help loosen a stuck choke.

13. Bad Gas Cap

The gas cap is designed to allow air to pass through the cap. When this vent is plugged, the fuel tank will form a vacuum not allowing gas to flow out of the tank.

Your Bobcat zero-turn may have started with a bad gas cap, but it will shut down once it has run for a while. This is because a vacuum will form in the tank when air isn’t able to pass through the cap.


14. Plugged Mower Deck

A plugged mower deck can make your engine work hard, overheat, and shut down.

When grass collects under your mower deck, extra strain is put on the engine when it must turn the blades through a deck full of debris. Dull mower blades can further magnify the problem.

SOLUTION: Regularly scrape your mower deck and sharpen your mower blades. Not only will a clean deck not put extra strain on your engine, but it will also provide you with a nicer cut.

The deck uses the blades and area under the deck to create air movement to lift and cut your grass.