How to Troubleshoot A Push Mower That Won't Start?

19 minutes read

If you're facing issues with your push mower not starting, there are a few troubleshooting steps you can take to identify and potentially fix the problem.

  1. Check spark plug: One common reason for a mower not starting is a faulty spark plug. Remove the spark plug wire and unscrew the plug. Examine the tip and clean or replace it if necessary. Reinstall the plug and reconnect the wire.
  2. Inspect the fuel system: Ensure there is sufficient fuel in the tank. If you suspect old fuel is the issue, drain the tank and replace it with fresh gasoline. Check the fuel lines for any signs of damage or blockage. If needed, clean or replace the fuel filter.
  3. Clean or replace air filter: A dirty or clogged air filter can prevent the engine from starting. Remove the air filter cover and inspect the filter. If it is dirty, clean it with soapy water or replace it with a new one.
  4. Confirm proper starting procedure: Review the operator's manual to ensure you are following the correct starting procedure. Each mower may have specific instructions regarding choke, primer bulb, throttle, or safety mechanisms.
  5. Check safety features: Some mowers have safety features like a blade engagement lever or a presence of a control handle. Make sure these are properly engaged or disengaged (as per the manual) before attempting to start the mower.
  6. Test the ignition system: Inspect the ignition switch and wiring for any damage. If the switch is faulty, it may need to be replaced. Check for proper connection on all electrical contacts and clean if necessary.
  7. Check for clean carburetor: Over time, the carburetor can get clogged with dirt or debris, preventing fuel from reaching the engine. Inspect and clean the carburetor if needed, or consider using a fuel additive to clean the fuel system.
  8. Confirm safety interlock switches: Some push mowers have safety switches that engage when the handle is released or blades disengaged. Ensure these switches are functional and properly aligned.

If you've gone through these troubleshooting steps and the mower still won't start, it might be best to consult a professional or take the mower to a repair shop for further inspection and assistance.

Best Push Lawn Mowers of 2024

YARDMAX 21 in. 170cc 2-in-1 Gas Walk Behind Push Lawn Mower with High Rear Wheels

Rating is 5 out of 5

YARDMAX 21 in. 170cc 2-in-1 Gas Walk Behind Push Lawn Mower with High Rear Wheels

  • Single-lever deck adjustment for quickly setting your mow height
  • MAXFlow Deck Technology – volute spiral deck design for better airflow and mulching
  • Heavy-duty, 16-gauge stamped steel deck
  • Durable, one-piece seamless steel deck reduces vibration
  • Seven cutting heights from 1.25″ to 3.75″
  • Double-ball-bearing wheels for easy, smooth mowing with less pushing effort
  • Adjustable, durable 3-position handle height
  • Folds for space-saving storage
  • 7 in. front and 11 in. rear wheels for stability and control
PowerSmart Gas Lawn Mower 21 Inch 2-in-1 with 144CC 4-Stroke Engine, Push Mower Gas Powered DB2321CR

Rating is 4.9 out of 5

PowerSmart Gas Lawn Mower 21 Inch 2-in-1 with 144CC 4-Stroke Engine, Push Mower Gas Powered DB2321CR

  • 144CC OHV ENGINE: reliable engine, recoil starter for easy start, forced air cooling system continuously deliver unbeatable grass cutting effect.
  • 21 INCH CUTTING DECK: patented cutting system with 21 inch cutting deck, wider mowing path helps you trim sizable yard fast.
  • 2-IN-1 PUSH MOWER: side-discharge easily pass thick grasses for quickest mowing, mulching lawn mower minces grass into super-fine bits for recycle.
  • GRASS HEIGHT ADJUSTABLE: 6 positions for adjust cutting height from 1.5" to 3.9", suitable for all kinds of grasses.
BILT HARD Gas Lawn Mower 20 inch, 2 in 1 170cc 4-Stroke OHV Engine Cordless Lawnmower, 8 Adjustable Cutting Heights Push Mowers for Lawn, Yard and Garden

Rating is 4.8 out of 5

BILT HARD Gas Lawn Mower 20 inch, 2 in 1 170cc 4-Stroke OHV Engine Cordless Lawnmower, 8 Adjustable Cutting Heights Push Mowers for Lawn, Yard and Garden

  • Auto Choke Engine - 170cc 4-stroke OHV engine, 6.5 torque, 20 inch cutting deck.
  • Cutting Height - 8-position single lever four-wheel synchronized height adjustment from 1.2" to 3.2".
  • Mowing Convenience - 7" rear/6“ front double ball-bearing wheels achieve smooth movement, comfortable foam-wrapped angled grip eliminates grasp fatigue.
  • Durable Cutting Deck: 20" cutting deck and specialized blade delivering a clean, even cut. Enjoy years of high efficient mowing with superior cutting quality
Greenworks 40V 16" Cordless (Push) Lawn Mower (75+ Compatible Tools), 4.0Ah Battery and Charger Included

Rating is 4.7 out of 5

Greenworks 40V 16" Cordless (Push) Lawn Mower (75+ Compatible Tools), 4.0Ah Battery and Charger Included

  • CORDLESS LAWN MOWER – Get more done, faster, with Greenworks electric lawn mowers. This 40v push lawn mower provides the power you need with up to 45 minutes of runtime on a fully charged 4.0Ah battery. The battery completely charges in 120 minutes.Brushless motor : No
  • LIGHTWEIGHT, EASY TO USE – A lightweight 16” cutting deck allows for easy maneuvering through small to medium yards (up to ½ acre) more efficiently. Easy push button start and lighter weight make it a great choice for your lawn.
  • VERSATILE – Battery powered lawn mower has a single lever 5-position height adjustment with a cutting height range from 1-1/4" to 3-3/8" for the best cut in all environments. The 2-in-1 feature offers versatile use with mulching and rear bagging options.
  • MAINTENANCE FREE – This walk behind lawn mower is virtually maintenance free, with no gas, no oil and no emissions. It starts instantly and is quiet but delivers gas-like power for your toughest projects.
Yard Machines 11A-02BT729 20-in Push Lawn Mower with 125cc Briggs & Stratton Gas Powered Engine, Black and Red

Rating is 4.6 out of 5

Yard Machines 11A-02BT729 20-in Push Lawn Mower with 125cc Briggs & Stratton Gas Powered Engine, Black and Red

  • A 125cc OHV Briggs & Stratton engine delivers reliable power to quickly tackle your yard
  • Push mower ideal for small yards with minimal obstacles
  • 20-in. deck with side discharge to efficiantly spread grass clippings
  • 7-in wheels provide reliable traction to navigate your yard
  • Choose from 3 cutting heights
BLACK+DECKER Electric Lawn Mower, 10-Amp, Corded (BEMW472BH)

Rating is 4.5 out of 5

BLACK+DECKER Electric Lawn Mower, 10-Amp, Corded (BEMW472BH)

  • Lightweight corded electric mower gasless 10 Amp 15 inch electric mower for powering through rough grass.Ideal for 1/8 acre.Voltage : 120 V. Product Application : Cleaning.
  • Comfort grip bike handlebar design reduces friction and enhances maneuverability for small lawns
  • Enhanced clipping collection winged blade yields 30% better clipping collection
  • Push button start no-hassle startup easy-to- use features
  • Adjustable cutting height 6 adjustable cutting heights ranging from 1 inch to 3 inch
CRAFTSMAN Gas Powered Lawn Mower, 21-inch Push Mower, 140cc (M105)

Rating is 4.4 out of 5

CRAFTSMAN Gas Powered Lawn Mower, 21-inch Push Mower, 140cc (M105)

  • POWERFUL ENGINE: 140cc BRIGGS & STRATTON engine with auto-choke
  • MOWING CONVENIENCE: 21 in., 3-in-1 convertible deck lets you side discharge, mulch, or rear bag grass clippings
  • CLIPPING COLLECTION: Rear bag collects grass clippings for easy cleanup or composting
  • HEIGHT ADJUSTMENT: Dual-lever, 6-position height adjustment makes it easy to change cutting heights from 1.25 in. to 3.75 in. high
  • COMFORT: Adjustable loop handle for comfort while mowing. MULCH KIT: Included to help put nutrients back into soil for a healthy lawn
BLACK+DECKER 3-in-1 String Trimmer/Edger & Lawn Mower, 6.5-Amp, 12-Inch, Corded (MTE912) (Power cord not included), Black/Red

Rating is 4.3 out of 5

BLACK+DECKER 3-in-1 String Trimmer/Edger & Lawn Mower, 6.5-Amp, 12-Inch, Corded (MTE912) (Power cord not included), Black/Red

  • 3N1 DESIGN – Electric mower easily converts to string trimmer and edger via a built-in foot pedal for versatile use.
  • 6.5 AMP MOTOR – Supplies the ideal amount of power when trimming grass, weeds, and overgrowth.
  • GEAR DRIVE TRANSMISSION – For tackling tougher, thicker grass without getting bogged down.
  • AFS AUTOMATIC FEED SPOOL – Continuously feeds trimmer line without bumping for seamless, uninterrupted trimming.
  • ADJUSTABLE MOWER DECK AND TRIMMER HANDLE – Lawn mower deck and string trimmer handle are adjustable for ideal grass- cutting height and added comfort.
  • CORDED – Corded design offers unlimited runtime for even the biggest jobs.
  • INCLUDES – (1)GH912 trimmer/edger, (1) MTD100 detachable mower deck, (1) AF-100 spool, (1) auxiliary handle, (1) guard.
  • Note: Item requires power cord. Power cord not included

How to test the charging system in a push mower?

To test the charging system in a push mower, you can follow these steps:

  1. Start the engine: Make sure the push mower is in a safe location, then start the engine by pulling the recoil cord or using the electric start, depending on the model.
  2. Check the battery voltage: Use a multimeter to measure the voltage across the battery terminals. It should be around 12 volts for a 12-volt battery. If the voltage is significantly lower, it may indicate a problem with the charging system.
  3. Test the alternator: Locate the alternator on the mower engine. It is usually a small, round component with wires connected to it. With the engine running, use the multimeter to measure the voltage across the alternator terminals. It should be around 13-14 volts. If the voltage is significantly lower or there is no voltage at all, it may suggest a faulty alternator.
  4. Inspect the wiring: Check the wires connecting the alternator to the battery for any signs of damage or loose connections. Ensure all the connections are tight and free from corrosion. If there are any issues, repair or replace the wiring as necessary.
  5. Test the battery charging: Start the engine and let it run for a few minutes. Then, measure the voltage across the battery terminals again. If the voltage has increased, it indicates that the charging system is working properly. If the voltage remains the same or decreases, it suggests a problem with the charging system.
  6. Consult a professional: If you are unable to identify or fix any issues with the charging system, it is advisable to take the push mower to a professional technician for further troubleshooting and repair.

Note: Ensure all safety precautions are followed while working on the mower, such as disconnecting spark plugs, wearing protective gear, and referring to the mower's manual for specific instructions.

What are some symptoms of a worn-out piston or piston rings?

Some symptoms of a worn-out piston or piston rings are:

  1. Engine misfires: A worn-out piston or piston rings can lead to inefficient combustion, causing the engine to misfire. This is usually characterized by a noticeable loss of power, rough engine idle, and intermittent stumbling or hesitating during acceleration.
  2. Excessive oil consumption: If the piston rings are worn, they may not be able to create a proper seal, resulting in oil leaking into the combustion chamber. This can lead to increased oil consumption and visible blue smoke from the exhaust.
  3. Decreased engine performance: Worn-out pistons or piston rings can lead to reduced compression in the cylinders. This can cause a decrease in engine performance, including reduced power, slower acceleration, and difficulty maintaining higher speeds.
  4. Engine noise: As the piston and piston rings wear out, they may create excessive noise, often described as a knocking or tapping sound. This noise is usually more noticeable at lower engine speeds and can indicate a loss of compression in the cylinder.
  5. Poor fuel efficiency: When the piston rings are worn, the engine may not be able to maintain proper compression, leading to decreased fuel efficiency. This can result in increased fuel consumption and reduced mileage.

It is important to note that these symptoms can also be caused by other issues, so it's best to have a professional mechanic diagnose the problem to determine the exact cause.

What is the significance of the flywheel key in a push mower?

The flywheel key in a push mower is a small metal piece that links the flywheel to the crankshaft. Its significance is to ensure proper timing and synchronization between the engine's valves and the piston's movement.

The flywheel key is designed to fit in a specific slot on both the flywheel and the crankshaft. It prevents any slippage or misalignment between these two components during operation. This alignment is crucial because it determines the opening and closing of the engine's valves at the correct time.

If the flywheel key becomes damaged or shears off, the timing between the valves and piston can be disrupted. This can result in various issues, such as loss of power, difficulty starting the engine, or even engine damage.

Replacing a damaged flywheel key is a relatively simple task that involves removing the flywheel and installing a new key in its designated slot. Ensuring the proper installation and alignment of the flywheel key is essential for maintaining the efficient and reliable operation of a push mower.

What are the steps for sharpening a dull mower blade?

  1. Preparation: Ensure the mower is turned off, the spark plug is disconnected, and the fuel tank is empty to prevent any accidents. Wear protective gloves and eye goggles to ensure personal safety.
  2. Remove the blade: Locate the mower blade underneath the mower deck. Use a wrench or socket set to loosen and remove the nut or bolt securing the blade to the mower deck. Carefully slide the blade out from under the mower deck.
  3. Clean the blade: Use a wire brush or a stiff bristle brush to remove any built-up grass, debris, or rust from the blade. It is important to clean the blade thoroughly to ensure a precise sharpening.
  4. Inspect the blade: Check for any severe damage, bends, or cracks. If the blade is severely damaged, it is recommended to replace it rather than attempting to sharpen it.
  5. Choose a sharpening method: There are several methods available for sharpening a mower blade, including using a file, a grinding wheel, or a professional sharpening service. Choose the method based on your preference and available tools.
  6. File sharpening method: Secure the blade in a vise to hold it steady for sharpening. Use a flat file to sharpen the blade, following the original cutting angle. File in one direction only, using long, smooth strokes along the cutting edge of the blade. Repeat the filing process until the cutting edge is sharp.
  7. Grinding wheel method: Secure the blade in a vice and use an angle grinder or bench grinder with a sharpening stone attachment. Hold the grinder steady and slowly move the cutting edge of the blade against the grinding wheel at the same angle as the original bevel. Repeat the grinding process until the cutting edge is restored and sharp.
  8. Balance the blade: After sharpening, it is important to balance the blade to ensure smooth and efficient operation. Hang the blade on a nail or use a balancing tool to check if it remains level. If one side is heavier, gently grind or file a small amount of metal from the heavier end until the blade balances.
  9. Reinstall the blade: Slide the sharpened blade back under the mower deck, ensuring it is correctly aligned with the mounting holes. Use the wrench or socket set to tighten the nut or bolt securely, making sure the blade is held firmly.
  10. Test the mower: Reconnect the spark plug and fill the fuel tank if required. Start the mower and allow it to run for a few minutes to ensure the blade is functioning properly and cutting evenly.

Remember to always consult the specific instructions in your mower's manual and exercise caution when sharpening the blade. If you are unsure or uncomfortable with the process, consult a professional.

What is the proper fuel mixture for a push mower?

The proper fuel mixture for a push mower typically consists of gasoline and engine oil. However, the specific ratio of gasoline to engine oil may vary depending on the manufacturer's instructions.

Commonly, a 2-stroke push mower requires a fuel mixture of gasoline and oil at a ratio of 50:1, meaning 50 parts gasoline to 1 part oil. This ratio ensures proper lubrication of the engine while minimizing smoke and emissions.

On the other hand, a 4-stroke push mower usually operates on pure gasoline, without the need for mixing oil. In this case, you should use regular unleaded gasoline with an octane rating of 87 or higher.

It is important to refer to the owner's manual or manufacturer's instructions to determine the exact fuel mixture requirement for your specific push mower model, as it can vary.

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