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Common Lawn Mower Problems: Solved!

There are many problems that are common to most lawn mowers on the market today. I have put together a list of issues that are most problematic over my years of working with lawn mower owners. Many of these items can be prevented with your annual mower maintenance.

The most common lawn mower problems are: 

  • Lawn mower won’t start
  • Lawn mower loses power & dies when mowing 
  • Lawn mower smokes 
  • Lawn mower has a weak hydrostatic transmission
  • Lawn mower won’t drive straight or steer right or left
  • Lawn mower won’t move
  • Lawn mower is cutting uneven
  • Lawn mower is leaking gas

Most of these problems can be easily fixed by you. I’ll go over the common issues and explain the solutions so you can determine whether you want to tackle the task or not.

Always follow safety guidelines outlined in your mower’s operator’s manual to prevent injury while working on your lawn mower.

how to fix common lawn mower problems

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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, knowledge or are not in the condition to perform the repair safely.

Lawn Mower Won’t Start 

A lawn mower may not start due to old fuel, dirty carburetor, bad fuel pump, dirty spark plug, dead battery, faulty safety switch or bad ignition switch.

Detailed information can be found at:
Lawn Mower Won’t Start: Solved!

CauseReason for ProblemSolution
No gas in the fuel tankFuel tank is emptyFill with fresh fuel
Bad or old fuelFuel breaks down overtime making your fuel less efficient and prone to clogging the fuel systemDrain the fuel tank and fill 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 capThe vent in the cap can get clogged causing your tank to form a vacuum restricting fuel flowUse a thin piece of wire to try to clear the clogged vent. Replace the cap if needed.
Bad spark plugExcessively dirty or broken spark plug; bad connection; not gapped correctlyReplace with a new spark plug, secure connections and ensure it is gapped to manufacturer specifications
Plugged air filterDirt and grass can plug the air filter preventing air flowRemove the filter and clean it. Replace the filter if it is in bad condition.
Plugged fuel filterA dirty fuel filter will restrict fuel flowReplace the fuel filter
Bad fuel pumpA failed or leaking fuel pump will no longer create pressure needed to pump fuelReplace the fuel pump
Blocked fuel linesBad fuel deposits and dirt can build up and clog the fuel lines preventing the engine from getting the required fuelUse a carb cleaner and compressed air to clear the clog out of the fuel line. Replace line if necessary.
Dirty carburetorThe carburetor can become dirty and clogged due to bad fuel and ethanol deposits preventing fuel flowClean the components making up the carburetor. Replace if needed.
Bad battery or loose & dirty terminalsA dead battery, loose cables or corroded terminals can cause starting problemsCharge your battery and replace if it won’t hold a charge. Make sure your cables are tight and clean the corrosion from terminals.
Bad safety switchSafety switches is a safety measure that exist 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 coilYour mower will not start when either the ignition switch or coil is badTest and replace a bad switch
Broken recoilA pull start mower may have a damaged or broke recoil preventing the recoil to initiate starting your engineCheck recoil to see if it can be restrung or broke parts, like the pulley, can be replaced. Replace the recoil assembly if needed.
Bad Starter SolenoidAn ignition switch that hums when turning the key indicates you may have a problem with the starter solenoid causing a starting problem.Test the starter solenoid and replace if bad.
Bad charging systemA charging system that can’t keep your mower charged and is constantly draining the battery must be repaired to prevent starting problems.Take your lawn mower to your local lawn mower dealer for assistance identifying which part of the charging system has failed.
Reasons a Lawn Mower Won’t Start

Lawn Mower Loses Power and Dies While Mowing 

Your lawn mower may die while mowing when your fuel system or air filtration system is clogged. This could be from a plugged air filter, dirty carburetor or bad fuel. You’ll also want to take a look at everything that may be failing to keep your keep your engine cool like dirt and grass packed around the engine or broke cooling fins.

Detailed information can be found at:
Your Lawn Mower Dies While Mowing

CauseReason for ProblemSolution
Bad fuelFuel breaks down overtime making your fuel less efficient and prone to clogging the fuel system and engine damageDrain the fuel tank and fill with fresh fuel. Use a fuel additive like Sea Foam to stabilize the fuel and assist with cleaning the fuel system
Plugged air filterDirt and grass can plug the air filter preventing air flowRemove the filter and clean it. Replace the filter if it is in bad condition.
Dirty or broken cooling finsCooling fins get packed with dirt, oil and grass not allowing air to effectively cool the engine blockReplace broken fins and clean the cooling fins.
Clogged fuel linesBad 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 carburetorThe carburetor can become dirty and clogged due to bad fuel and ethanol deposits preventing fuel flowClean all of the components making up the carburetor. Replace if needed.
Reasons a Lawn Mower Dies While Mowing

Lawn Mower is Smoking

Some of the same reasons as mentioned above for your lawn mower shutting down while mowing can be found the reasons your lawn mower is smoking as well. Smoke can develop when your engine is running too rich and you’re burning more fuel than air. Another reason you may notice smoke is when is engine oil is burning off due to an oil leak, insufficient oil level or an internal engine problem.

Detailed information can be found at:
Why Your Lawn Mower is Smoking

CauseReason for ProblemSolution
Plugged air filterDirt and grass can plug the air filter preventing air flowRemove the filter and clean it. Replace the filter if it is in bad condition.
Too much oil in the crankcaseExcessive oil can cause pressure to build in the engine allowing oil to get into the cylinder through the valve trainDrain a little engine oil until it is at the manufacturers recommended oil level.
Engine oil level is too lowLack 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 have this fix your engine problem.
Internal problems including the piston ring, valve train or engine gasketInternal engine problems can have a detrimental effect on your mower if they are not caught soon enough and fixed.Bring your lawn mower to your local small engine repair shop for troubleshooting
Reasons a Lawn Mower is Smoking

Weak Hydrostatic Transmission on a Lawn Mower 

A lawn mower with a hydrostatic transmission may experience a weak transmission when the hydraulic oil is low or old. A bad hydro belt or pulley can also make your transmission seem like it weak.

Note: Some transmissions are non-serviceable. This means you are unable to change the hydraulic oil because the system is sealed. Bring your mower to your local lawn mower repair shop when you have problems with your hydraulic system.

CauseReason for ProblemSolution
Bad drive beltA bad drive belt can cause your pump not to work efficientlyReplace a frayed, cracked or worn belt
Bad tensioner pulleyWhen a tensioner pulley fails, it fails to keep tension on the drive beltReplace the pulley and grease the tensioner arm
Low or old hydraulic oilLow or old hydraulic oil can fail to lubricate the hydraulic system causing your hydraulic system to seem weakChange your hydraulic oil at regularly intervals as recommended by the manufacturer.
Check your hydraulic oil periodically to ensure your hydraulic fluid is full.
Reasons a Lawn Mower’s Hydrostatic Transmission Seems Weak

Lawn Mower Won’t Drive Straight or Won’t Turn Left or Right

It’s frustrating to always have to compensate for your lawn mower pulling a little to the left or a little to the right or your mower just won’t turn left or right when you move the steering wheel. There are some simple adjustments you can make to correct your mower’s steering problem.

CauseReason for ProblemSolution
Incorrect tire pressureUnequal tire pressure can cause your mower to pull to one side.Check tire pressures and keep them filled to the manufacturers spec. Tires on each side of your mower requires equal pressures.
Bad dampers on zero turnBad dampers will cause your mower to jerk to one side when moving forwardReplace with a new damper
Tracking adjustment needed on zero turnWhen one tire is moving faster than the other, your mower can pull to one sideAdjust speed adjustment bolt to change the rotation speed of the tire. Refer to your owner’s manual.
Worn or loose steering components in riding mowerWorn bushings, washers and gears can cause your mower to not steer one way or the otherInspect and replace the parts that failed on your steering system
Reasons a Lawn Mower Won’t Drive Straight or Steer Correctly

Lawn Mower Won’t Move

There are many reasons why a hydrostatic lawn mower will not move. I have listed below the reason why your lawn mower may not move, including old hydraulic oil or a low oil level.

Hydrostatic transmissions are used in most current riding mowers and zero turn mowers, however there are different procedures and steps to servicing each type. Refer to your owner’s manual for details on caring for your hydraulic system.

Detailed information can be found at:
9 Reasons Your Mower Won’t Move or Go Forward

CauseReason for ProblemSolution
Drive release lever in the wrong positionThe drive release lever allows hydrostatic mowers to roll freelyThe drive release lever must be in the operating position.
Missing key in the axleYour riding mower may have a small key in the axle that may have fallen out of placeReplace the key in the axle
Drive pump belt is wornThe 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 pulleyThe bearing in the tensioner pulley can failReplace the tensioner pulley
Missing idler arm springIf the idler arm spring breaks or goes missing, it can no longer place tension on the drive beltReplace the broken or missing spring
Low or old hydraulic oilLow or old hydraulic oil can fail to lubricate the hydraulic system causing your hydraulic system to seem weakChange your hydraulic oil at regularly intervals as recommended by the manufacturer.
Check your hydraulic oil periodically to ensure your hydraulic fluid is full.
Hot hydraulic fluidHot hydraulic fluid can be a sign of damage to your hydrostatic transmission systemLet your hydraulic oil cool. If you find your mower runs fine when it is cold, but does becomes weak when the hydraulic system gets hot, have your mower checked at your local lawn mower dealership.
Air in the hydraulic systemAir must be bled from the hydraulic system after changing your hydraulic fluid or the mower will not be able to move at normal speedsFollow the manufacturer’s procedures for changing hydraulic fluid and bleeding air from the system in your owner’s manual.
Reasons a Lawn Mower Will Not Move or Go Forward

Lawn Mower is Vibrating

There are many reasons a lawn mower may start to vibrate. You could have some missing or broken parts or it could be from debris that is stuck in the mower. It’s important to look your mower over closely as the littlest items can cause a big vibration.

Detailed information can be found at:
How to Stop Your Lawn Mower from Shaking & Vibration

CauseReason for ProblemSolution
Loose or missing engine mounting boltsEngine bolts are used to reduce vibration of the mower when the engine is runningSecure engine bolts and replace any missing bolts
Clutch is badWhen 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 bladesDamaged and unbalanced blades can send a vibration through your mower. Blades must be balanced before installingReplace any damaged blades and make sure they are balanced.
Material wrapped around the blade spindleForeign materials like string or long weeds can get wrapped around your blade shaft causing vibrationRemove all debris and items wrapped around the blade shaft. Check for spindle damage.
Bad spindle housing bearingsVibration can be caused by a bad bearing in the spindle housing.Replace bearing in the spindle housing or replace the whole spindle housing assembly
Worn pulleys or deck beltCheck deck belt and pulleys for wearing of the belt and bearing failure in the pulleysReplace any damaged or worn belts and pulleys
Debris lodged in mowerThe smallest little things can cause your lawn mower 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.
Reasons a Lawn Mower is Vibrating

Lawn Mower Has a Bad or Uneven Cut

An uneven cut with your lawn mower doesn’t always indicate a problem in the mower deck. It can be something as simple as a low tire that can make you’re your mower not sit level. Always check the tire pressure first and then move on to looking at your mower deck.

Detailed information can be found at:
Reasons a Lawn Mower Cuts Uneven

Worn mower bladeUneven tire pressuresEngine speed is too low
Bent mower bladeUnleveled mower deckGround speed is too fast
Blade installed wrongBent blade spindle or spindle bearingDamaged deck shell
Clogged Mower DeckWorn deck pulleys or beltOperator error
Reasons a Lawn Mower is Cutting Uneven

Lawn Mower is Leaking Gas

It can be difficult to find fuel leaks in your lawn mower because fuel evaporates into the air. By the time you realize you have a leak, there may not be a large wet spot giving you a clue to the area of the leak. Your only clue may be the strong odor left in your garage.

When looking for an oil leak, follow your fuel lines starting at the fuel tank. Check every component that makes up your fuel system for leaks.

Detailed information can be found at:
This is Where a Lawn Mower is Leaking Gas

CauseReason for ProblemSolution
Dirty of Failed CarburetorThe carburetor can collect a buildup of substances remaining from old gas that can cause blockages or parts failuresClean the carburetor and replace any damaged parts
Old Fuel FilterFilter can become pluggedReplace fuel filter
Bad Fuel PumpPump can wear and deteriorate over time and may begin leaking at the seamsReplace the fuel pump
Bad Fuel TankA 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 ValveMetal and plastic shut-off valves are prone to leakingReplace the shut-off valve
Cracked Fuel LinesRubber fuel lines become dry and cracked causing gas to leakReplace the fuel lines
Cracked Primer BulbThe rubber of the primer bulb can begin leaking when it cracks or isn’t attached well to the fuel hose.Replace the primer bulb
Bad Seal in the Gas CapThe gas cap seal can fail and no longer seal allowing gas to splash out of the fuel tank around the gas capReplace the gas cap
Places a Lawn Mower May Be Leaking Gas