9 Common Zero Turn Problems: How to Fix Them
Owning a zero-turn lawn mower doesn’t come without its problems. Owners must accept the fact that some items on their zero-turn will fail over time.
With a good maintenance routine, you can prevent some of these problems. However, if you own the same zero turn long enough, components will eventually begin to wear and fail.
Some of the most common zero-turn problems and owner complaints are:
- Zero-turn won’t start
- Zero-turn dies while mowing
- Zero-turn is smoking
- Zero-turn has a weak hydrostatic transmission
- Zero-turn won’t drive straight or steer correctly
- Zero-turn won’t move
- Zero-turn is shaking or vibrating
- Zero-turn is cutting uneven
- Zero-turn is leaking gas
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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.
Table of Contents
Zero Turn Lawn Mower Problems
Zero Turn Mower Won’t Start
Your zero-turn lawn mower may not start because of fuel system problems such as bad fuel, a dirty carburetor, or a bad fuel pump. A bad spark plug, battery, safety switch, and ignition switch can also cause your zero-turn not to start.
Detailed information can be found at:
Why Your Zero Turn Won’t Start
| Cause | Reason for Problem | Solution |
| No gas in the fuel tank | Fuel tank is empty | Fill with fresh fuel |
| Bad or old fuel | Fuel breaks down overtime making your fuel less efficient and prone to clogging the fuel system | Drain the fuel tank and fill it with fresh fuel. Use a fuel additive like Sea Foam to stabilize the fuel and assist with cleaning the fuel system. Use the right fuel. |
| Faulty or clogged fuel cap | The vent in the cap can get clogged causing your tank to form a vacuum restricting fuel flow | Use a thin piece of wire to try to clear the clogged vent. Replace the cap if needed. |
| Bad spark plug | Excessively dirty or broken spark plug; bad connection; not gapped correctly | Replace with a new spark plug, secure connections, and ensure it is gapped to manufacturer specifications |
| Plugged air filter | Dirt and grass can plug the air filter preventing airflow | Remove the filter and clean it. Replace the filter if it is in bad condition. |
| Plugged fuel filter | A dirty fuel filter will restrict fuel flow | Replace the fuel filter |
| Bad fuel pump | A failed or leaking fuel pump will no longer create the pressure needed to pump fuel | Replace the fuel pump |
| Blocked fuel lines | Bad fuel deposits and dirt can build up and clog the fuel lines preventing the engine from getting the required fuel | Use a carb cleaner and compressed air to clear the clog out of the fuel line. Replace the line if necessary. |
| Dirty carburetor | The carburetor can become dirty and clogged due to bad fuel and ethanol deposits preventing fuel flow | Clean the components making up the carburetor. Replace if needed. |
| Bad battery or loose & dirty terminals | A dead battery, loose cables, or corroded terminals can cause starting problems | Charge your battery and replace it if it won’t hold a charge. Make sure your cables are tight and clean the corrosion from terminals. |
| Bad safety switch | Safety switches are a safety measure that exists to prevent your mower from starting in certain situations. When a switch fails, your mower may not start. | Test and replace faulty safety switch |
| Bad ignition switch or coil | Your mower will not start when either the ignition switch or coil is bad | Test and replace a bad switch |
Zero Turn Mower Starts Then Dies
Some of the same items that cause your zero-turn to not start are also items that can cause your mower to die while mowing. When your mower can’t get enough air and fuel it will shut down.
You could have a clog that moved through your fuel system or your air filter is blocking air.
An issue that can present itself after mowing for a little while is a bad fuel cap that doesn’t allow air to pass through the cap’s vent. A plugged cap causes your fuel tank to form a vacuum so fuel is unable to flow out of the tank.
When your engine overheats, your mower can shut down. Inspect your cooling fins to ensure they are not broken or plugged with dirt. The fins keep air moving around your engine block and cylinder head.
Detailed information can be found at:
Zero Turn Mower Starts Then Dies
| Cause | Reason for Problem | Solution |
| Bad fuel | Fuel breaks down overtime making your fuel less efficient and prone to clogging the fuel system and engine damage | Drain the fuel tank and fill it with fresh fuel. Use a fuel additive like Sea Foam to stabilize the fuel and assist with cleaning the fuel system |
| Plugged air filter | Dirt and grass can plug the air filter preventing airflow | Remove the filter and clean it. Replace the filter if it is in bad condition. |
| Dirty or broken cooling fins | Cooling fins get packed with dirt, oil, and grass not allowing air to effectively cool the engine block | Replace broken fins and clean the cooling fins. |
| Clogged fuel lines | Bad fuel deposits and dirt can build up and clog the fuel lines preventing the engine from getting the required fuel. | Use a carb cleaner and compressed air to clear the clog out of the fuel line |
| Dirty carburetor | The carburetor can become dirty and clogged due to bad fuel and ethanol deposits preventing fuel flow | Clean the components making up the carburetor. Replace if needed. |
Zero Turn Lawn Mower Smokes
It can be quite alarming when you see smoke emitting from your zero-turn mower. A plugged air filter, wrong engine oil level, or other internal engine problems can cause smoking.
When your engine doesn’t receive the correct air-to-fuel ratio or oil becomes hot and burns off, your zero-turn will begin to smoke.
Detailed information can be found at:
Reasons Your Lawn Mower May Be Smoking
| Cause | Reason for Problem | Solution |
| Plugged air filter | Dirt and grass can plug the air filter preventing airflow | Remove the filter and clean it. Replace the filter if it is in bad condition. |
| Too much oil in the crankcase | Excessive oil can cause pressure to build in the engine allowing oil to get into the cylinder through the valve train | Drain a little engine oil until it is at the manufacturer’s recommended oil level. |
| Engine oil level is too low | Lack of oil can increase friction in your engine causing extreme heat. | Bring to a small engine repair shop to inspect engine damage. You can try adding oil, but it is often too late to this fix your engine problem. |
| Internal problems including the piston ring, valve train, or engine gasket | Internal engine problems can have a detrimental effect on your mower if they are not caught soon enough and fixed. | Bring your zero-turn to your local dealer or small engine repair shop for troubleshooting |
Zero Turn Mower Has a Weak Hydrostatic Transmission
Zero-turn mowers have intervals when you must change your hydraulic fluid for the best performance. When you run a low level of hydro oil or your oil is getting aged, you can develop transmission problems.
Your zero-turn’s transmission may seem weak. Weakness can also be caused by a bad drive belt or tensioner pulley.
| Cause | Reason for Problem | Solution |
| Bad drive belt | A bad drive belt can cause your pump not to work efficiently | Replace a frayed, cracked, or worn belt |
| Bad tensioner pulley | When a tensioner pulley fails, it fails to keep tension on the drive belt | Replace the pulley and grease the tensioner arm |
| Low or old hydraulic oil | Low or old hydraulic oil can fail to lubricate the hydraulic system causing your hydraulic system to seem weak | Change your hydraulic oil at regular intervals as recommended by your zero-turn manufacturer. Check your hydraulic oil periodically to ensure your hydraulic fluid is full. |
Zero Turn Mower Won’t Drive Straight or Steer Correctly
| Cause | Reason for Problem | Solution |
| Incorrect tire pressure | Unequal tire pressure can cause your mower to pull to one side. | Check tire pressures and keep them filled to the manufacturer’s spec. Tires on each side of your mower require equal pressure. |
| Bad dampers on zero turn | Bad dampers will cause your mower to jerk to one side when moving forward | Replace with a new damper |
| Tracking adjustment needed on zero-turn or stand-on mower | When one tire is moving faster than the other, your mower can pull to one side | Adjust the speed adjustment bolt to change the rotation speed of the tire. Refer to your owner’s manual. |
Zero Turn Lawn Mower Won’t Move
Old hydraulic oil or an insufficient oil level can also cause your zero-turn to not move or, if it does, it may move slowly. Check the drive belt, tensioner pulley, and spring. If any of these items are worn or missing, your zero-turn mower may not move.
Another item to check is the hydraulic release lever. You may have recently had to manually move your mower and use the drive release lever to release the hydros.
Make sure your drive release levers are in the operating position. If they are not, your mower will not move.
Detailed information can be found at:
Zero Turn Mower Won’t Move or Go Forward
| Cause | Reason for Problem | Solution |
| Drive release lever in the wrong position | The drive release lever allows hydrostatic mowers to roll freely | The drive release lever must be in the operating position. |
| Drive pump belt is worn | The mower won’t move if your drive belt has fallen off. It could also not move if the belt is worn. | Replace a worn or cracked belt. Make sure the belt is securely around the pulleys. |
| Bad tensioner pulley | The bearing in the tensioner pulley can fail | Replace the tensioner pulley |
| Missing idler arm spring | If the idler arm spring breaks or goes missing, it can no longer place tension on the drive belt | Replace the broken or missing spring |
| Low or old hydraulic oil | Low or old hydraulic oil can fail to lubricate the hydraulic system causing your hydraulic system to seem weak | Change your hydraulic oil at regular intervals as recommended by your zero-turn manufacturer. Check your hydraulic oil periodically to ensure your hydraulic fluid is full. |
| Hot hydraulic fluid | Hot hydraulic fluid can be a sign of damage to your hydrostatic transmission system | Let your hydraulic oil cool. If you find your mower runs fine when it is cold, but becomes weak when the hydraulic system gets hot, have your mower checked at your local zero-turn dealership or repair shop. |
| Air in the hydraulic system | Air must be bled from the hydraulic system after changing your hydraulic fluid or the mower will not be able to move at normal speeds | Follow the zero-turn manufacturer procedures for changing the hydraulic fluid and bleeding air from the system in your owner’s manual. |
Zero Turn Mower is Vibrating
There is always some vibration that comes from running the engine. However, there are times when you may feel a severe vibration that isn’t the typical vibration. This is something that needs to be addressed to minimize mower damage.
There are many things you need to check including engine mounting bolts, debris caught in the mower deck, and worn or damaged components.
Detailed information can be found at:
Your Zero Turn is Shaking & Vibrating
| Cause | Reason for Problem | Solution |
| Loose or missing engine mounting bolts | Engine bolts are used to reduce the vibration of the mower when the engine is running | Secure engine bolts and replace any missing bolts |
| Clutch is bad | When there is bearing failure and it falls out of the clutch it can cause vibration. A manual engagement clutch can have a bushing and linkages that can fail. | Replace the clutch |
| Unbalanced or damaged mower blades | Damaged and unbalanced blades can send a vibration through your mower. Blades must be balanced before installing | Replace any damaged blades and make sure they are balanced. |
| Material wrapped around the blade spindle | Foreign materials like string or long weeds can get wrapped around your blade shaft causing vibration | Remove all debris and items wrapped around the blade shaft. Check for spindle damage. |
| Bad spindle housing bearings | Vibration can be caused by a bad bearing in the spindle housing. | Replace the bearing in the spindle housing or replace the whole spindle housing assembly |
| Worn pulleys or deck belt | Check deck belt and pulleys for wearing of the belt and bearing failure in the pulleys | Replace any damaged or worn belts and pulleys |
| Debris lodged in mower | The smallest little things can cause your zero-turn to excessively vibrate. Check over your mower for debris stuck in the deck or mower. Don’t overlook the small stuff. | Check over your mower deck and mower for any place small items can be stuck in your mower. Remove these foreign materials. |
Zero Turn Mower Has a Bad or Uneven Cut
When your cut is uneven or just bad, you need to fix it so you can continue to have a great-looking lawn. There are many items that can affect cuts including low tire pressures, worn deck components, clogged mower deck, and incorrect operating procedures.
Detailed information can be found at:
Your Zero Turn Lawn Mower is Cutting Uneven
| Worn mower blade | Uneven tire pressures | Engine speed is too low |
| Bent mower blade | Unleveled mower deck | Ground speed is too fast |
| Blade installed wrong | Bent blade spindle or spindle bearing | Damaged deck shell |
| Clogged Mower Deck | Worn deck pulleys or belt | Operator error |
Zero Turn Mower is Leaking Gas
When you smell a strong odor or see spots of burnt grass in your yard, you need to follow your fuel lines out of the fuel tank to find a fuel leak. Leaks can be hard to find because fuel often evaporates and you’re left only with smelling gas fumes.
A common area where zero turns develop leaks is in the carburetor. The gasket around the carburetor bowl can become dry losing its sealing ability or the float can become stuck.
Old gas can also cause plastics to degrade in your components developing leaks in your fuel filter, fuel pump, or fuel tank seams.
Detailed information can be found at:
Your Zero Turn Mower is Leaking Fuel
| Cause | Reason for Problem | Solution |
| Dirty of Failed Carburetor | The carburetor can collect a buildup of substances remaining from old gas that can cause blockages or parts failures | Clean the carburetor and replace any damaged parts |
| Old Fuel Filter | Filter can become plugged | Replace fuel filter |
| Bad Fuel Pump | Pump can wear and deteriorate over time and may begin leaking at the seams | Replace the fuel pump |
| Bad Fuel Tank | A metal tank can develop a rust hole. A poly tank can leak at the seams of the tank. | Replace the fuel tank. Sometimes, a rust hole can be repaired if you can no longer find a replacement tank. |
| Bad Fuel Shut-Off Valve | Metal and plastic shut-off valves are prone to leaking | Replace the shut-off valve |
| Cracked Fuel Lines | Rubber fuel lines become dry and cracked causing gas to leak | Replace the fuel lines |
| Bad Seal in the Gas Cap | The gas cap seal can fail and no longer seal allowing gas to splash out of the fuel tank around the gas cap | Replace the gas cap |
Perform Regular Maintenance on Your Zero Turn
Taking time to check your mower before each mowing and performing routine service on your zero-turn will prevent some of these issues or allow you to catch the problems before they develop into costly repairs.
See my article on servicing your zero-turn for a list of items you need to check when performing routine maintenance.
