9 Lawn Mower Troubleshooting: Common Causes and How to Fix

1. Lawn Mower Won’t Start

• Out of fuel or old fuel: Check the tank and fill with fresh gasoline. Drain and replace fuel if it’s over 30 days old to avoid blockages.
• Dirty or faulty spark plug: Inspect and clean or replace the spark plug if worn or fouled. Ensure correct spark gap and tight installation.
• Clogged air filter: Replace or clean the air filter if dirty or oily to maintain proper airflow.
• Fuel not reaching engine: Check and clean or replace clogged fuel filter and fuel lines to ensure fuel flow.
• Dirty or blocked carburetor: Tap the carburetor to loosen blockage; if needed, remove and clean it with carburetor cleaner or replace it.
• Ignition switch malfunction: Test the ignition switch with a multimeter; replace if faulty to restore proper starting.

Read more: How to Clean A Snow Blower Carburetor 

2. Lawn Mower Starts Then Stops

• Stale or contaminated fuel: Old or dirty fuel can cause the engine to stall shortly after starting. Drain the fuel tank and refill it with fresh gasoline. Also, avoid storing fuel for long periods to prevent contamination.
• Clogged carburetor: Dirt and residue can block fuel flow inside the carburetor. Try tapping the side of the carburetor gently to loosen any blockage. If that doesn’t work, remove and clean it thoroughly using carburetor cleaner spray. In severe cases, a carburetor rebuild or replacement may be necessary.
• Blocked fuel lines or fuel cap: Fuel lines or the vent in the fuel cap can get clogged, restricting fuel flow. Inspect the fuel lines for cracks or debris and clear any blockages. Make sure the fuel cap vent is not sealed shut, allowing proper airflow.
• Overheating engine: Continuous use or insufficient cooling can cause the engine to overheat and shut down. Let the mower cool before restarting. Regularly clean air filters and check oil levels to prevent overheating.

3. Lawn Mower Vibrates Too Much

• Loose or damaged blade: A bent, dull, or unbalanced blade can cause excessive vibration. Inspect the blade, sharpen or replace it if needed, and make sure it’s securely tightened.
• Loose engine mounts or hardware: Check bolts and mounts holding the engine and mower deck. Tighten any loose parts to reduce vibration.
• Debris stuck under the deck: Grass clippings or debris buildup can throw the mower off balance. Clean the underside of the mower deck regularly.
• Worn or damaged belts: Worn belts can cause uneven operation and vibration. Inspect and replace belts if they show signs of wear or damage.
• Engine problems: Internal engine issues, such as misfiring or loose components, can also cause vibration. If other fixes don’t work, consider professional servicing.

4. Lawn Mower Cuts Unevenly or Poorly

• Dull or damaged blades: Blades that are dull, bent, or chipped won’t cut grass cleanly. Sharpen or replace the blades regularly for a smooth, even cut.
• Uneven mower deck: If the mower deck is tilted or damaged, it can cause uneven cutting. Check the deck level and adjust the height on both sides evenly.
• Incorrect cutting height: Setting the mower too low or too high can affect cut quality. Adjust the cutting height to suit your grass type and lawn condition.
• Clogged mower deck: Grass buildup under the deck can block blades and reduce cutting efficiency. Clean the underside of the mower after each use.
• Worn or loose parts: Loose blade bolts or worn mower components can cause uneven cutting. Inspect and tighten all parts regularly.

5. Lawn Mower Is Smoking

• Overfilled oil: Too much oil can cause smoke. Check and drain excess oil if needed.
• Burning grass or debris: Grass stuck on the engine or muffler can smoke when heated. Clean the mower thoroughly.
• Engine problems: Blue or white smoke may indicate engine oil burning due to worn piston rings or valve seals. This requires professional repair.

• Overfilled oil: Too much oil can cause smoke. Check and drain excess oil if needed.
• Burning grass or debris: Grass stuck on the engine or muffler can smoke when heated. Clean the mower thoroughly.
• Engine problems: Blue or white smoke may indicate engine oil burning due to worn piston rings or valve seals. This requires professional repair.

6. Lawn Mower Starter Rope Won’t Pull

• Rope is stuck or jammed: The rope may be caught inside the recoil starter. Remove the starter housing and check for obstructions.
• Broken or snapped rope: Replace the starter rope if it’s frayed or broken.
• Engine seized: If the engine won’t turn over, it may be seized or locked. Inspect and fix engine issues before pulling the rope.

7. Battery-Powered Lawn Mower Problems

• Battery not charged: Ensure the battery is fully charged before use.
• Faulty battery or charger: Test the battery and charger; replace if defective.
• Electrical connections: Check and clean battery terminals and wiring for corrosion or loose connections.
• Motor or controller issues: If the mower doesn’t start or runs poorly despite a good battery, the motor or control system may need professional servicing.

8. Loss of power: faulty governor or clogged exhaust

• Faulty governor: A malfunctioning governor can cause the engine to lose speed or power. Have a professional inspect and repair it if needed.
• Clogged exhaust/muffler: Carbon buildup or debris in the exhaust restricts airflow, reducing power. Clean or replace the muffler to restore proper function.

9. Pull cord issues: too loose or stuck

• Loose pull cord: The recoil spring may be loose or damaged. Adjust or replace the spring to restore proper tension.
• Stuck pull cord: The starter housing might have debris or damage causing the rope to jam. Inspect, clean, and lubricate the starter mechanism as needed.

10. FAQs about Lawn Mower Troubleshooting

10.1. Why does my lawn mower only run for a few seconds then die?

10.2. What is the first thing to check if a lawn mower won't start?

10.3. How do I know if my lawn mower fuel filter is clogged?