Troubleshooting Guide: What to Do When Your Lawn Mower Won’t Start

One of the most frustrating experiences for any homeowner is when their lawn mower refuses to start. It can put a halt to your plans of a neatly manicured lawn and leave you scratching your head in confusion. However, there are common reasons why a lawn mower won’t start, and knowing these may help you troubleshoot the issue effectively.

Checking the fuel and fuel system when lawn mower won’t start

When your lawn mower won’t start, the first section to troubleshoot is the fuel and fuel system. Here are some steps to follow in order to identify and address any issues in this area.

Step 1: Examine the level of fuel

Begin by checking the level of fuel in the tank. It may seem obvious, but sometimes this simple oversight can be the cause of the starting problem. Ensure that the fuel in the tank is plenty to power lawn mower. If the tank is empty, fill it up with fresh, clean fuel.

Step 2: Inspect the fuel lines

Next, inspect the fuel lines for any signs of damage or blockage. Over time, dirt, debris, and other contaminants can accumulate in the lines, causing clogs. Use a flashlight to examine the fuel lines closely. If you notice any blockages or damage, it may be necessary to Clean or change the fuel lines.

Step 3: Clean or change oil filter

Oil filter plays a crucial role in keeping the fuel system clean and free from contaminants. An obstructed or filthy fuel filter can prevent fuel from reaching the engine, causing starting problems. Remove oil filter and inspect it for any signs of clogging or damage. Clean or change the filter as needed to ensure proper fuel flow.

Inspecting spark plug when lawn mower won’t start

Faulty Spark plugs are yet another typical culprit for a lawn mower that won’t start. Spark plug comes in charge of igniting the engine’s fuel, and if it is shabby or broken, the engine may not start. Here’s how to inspect and address any issues with spark plug.

Step 1: Locate spark plug

Spark plugs are often located on the top or side of the engine cylinder. Refer to your lawn mower’s manual if you’re unsure about the exact location. Once you’ve found spark plug, remove the wire connected to it by gently pulling it off.

Step 2: Examine spark plug

Carefully remove spark plug using a spark plug socket or a wrench. Look for any damage indications in spark plug, such as a broken porcelain insulator or a worn-out electrode. If spark plug appears dirty or covered in carbon deposits, it may need to be cleaned or replaced.

Step 3: Clean or change spark plug

If spark plug seems dirty, you can clean it using a spark plug cleaner. Gently scrub away any carbon deposits or dirt to restore its functionality. If spark plug appears damaged or worn out, it is best to put a fresh one in its place. Reinstall spark plug—whether it is new or clean—with the engine, then reattach the wire.

Examining air filter when lawn mower won’t start

A clogged or dirty air filter can also contribute to starting problems in a lawn mower. Air filter prevents dust, dirt, and debris from entering the engine, but over time, it can become clogged and restrict airflow. Here’s how to inspect and address any issues with air filter.

Step 1: Locate air filter

Air filter usually housed in a rectangular or cylindrical box close to the carburetor or air intake. If you’re unsure of the precise position, consult lawn mower’s manual. Once you’ve found air filter, take off the cover or housing to access the filter.

Step 2: Inspect air filter

Examine the air filter carefully for any indications of debris, dirt, or dust. If the filter appears filthy or obstructed, it is likely affecting the airflow with the engine. A clogged air filter can prevent the proper mixture of air and fuel, leading to starting issues.

Step 3: Clean or change air filter

If air filter seems dirty, by lightly tapping it, you may clean it on a hard surface or by blowing away with compressed air the debris. However, should the filter be heavily blocked or harmed, it is best to put a fresh one in its place.. Install the clean or new air filter back into the housing, ensuring a snug fit.

Troubleshooting the ignition system when lawn mower won’t start

If the fuel, fuel system, spark plug, and air filter are all in a good state, but lawn mower still won’t start, it’s time to troubleshoot the ignition system. The spark required to ignite the gasoline in the engine is delivered by the ignition system. Here are some steps to take when troubleshooting the ignition system.

Step 1: Examine the ignition switch

Ensure that the ignition switch is in the “on” position. Sometimes, a slack or faulty ignition switch can prevent the engine from starting. Make sure the switch is securely connected and functioning properly.

Step 2: Inspect the ignition coil

The ignition coil generates the high voltage needed to create a spark. Over time, the coil can become worn out or damaged, leading to starting issues. Inspect the ignition coil for any signs of damage, such as cracks or corrosion. If the coil appears faulty, it may need to be replaced.

Step 3: Test spark plug wire

A faulty spark plug wire can also cause starting problems. Carefully remove spark plug wire from spark plug and check for any signs of damage. If the wire appears worn out or frayed, it is best to put a fresh one in its place.. Ensure the wire is securely connected to both spark plug and the ignition coil.

Cleaning or replacing the carburetor when lawn mower won’t start

The carburetor is a vital component of lawn mower’s engine, as it is responsible for mixing fuel and air in the correct proportions. If the carburetor becomes filthy or obstructed, it can prevent the engine from starting. Here’s how to Clean or change the carburetor when lawn mower won’t start.

Step 1: Remove the carburetor

Begin by disconnecting spark plug wire to ensure safety. Locate the carburetor, which is typically attached with the engine near air filter. Carefully remove the carburetor by disconnecting any mounting bolts or screws.

Step 2: Clean the carburetor

If the carburetor appears filthy or obstructed, it is best to clean it thoroughly. Use a carburetor cleaner and a small brush to clean up any dirt, debris, or varnish buildup. Pay close attention to the small openings and jets within the carburetor. Once cleaned, reassemble the carburetor and reinstall it with the engine.

Step 3: Replace the carburetor

If washing the carburetor does not resolve the starting problem, it may be necessary to put a fresh one in its place.. Ensure you purchase the correct carburetor for lawn mowers make and model. Follow the manufacturer’s instructions to install the new carburetor properly.


In conclusion, a lawn mower that won’t start might be annoying, but by following this troubleshooting guide, you can identify and address common issues. Start by checking the fuel and fuel system, inspecting spark plug, examining air filter, troubleshooting the ignition system, and cleaning or replacing the carburetor if necessary. Regular maintenance and proper care can help prevent starting problems and keep lawn mower running smoothly. Remember, if you are unsure about any repairs, it is always best to seek advice from an experienced professional for assistance.