What Should I Do if My Lawnmower Won't Start: A Complete Troubleshooting Guide

Nothing is more frustrating than pulling the starter cord on your lawnmower only to hear silence or sputtering when you're ready to tackle your weekend yard work. If you're wondering "what should I do if my lawnmower won't start," you're not alone. This common problem affects millions of homeowners every spring and throughout the mowing season.

Before you consider expensive repairs or buying a new mower, there are several simple troubleshooting steps you can take to diagnose and potentially fix the issue yourself. Most lawnmower starting problems stem from just a few common causes that are surprisingly easy to address.

Check the Fuel System First

The most frequent culprit when your lawnmower won't start is old or contaminated fuel. Gasoline begins to break down after just 30 days, creating gum and varnish that can clog your engine's fuel system.

Start by checking if there's fuel in the tank. If the tank is empty, add fresh gasoline. If you see old fuel that's been sitting for months, drain it completely and replace it with fresh gas. Old fuel often appears darker or has a sour smell compared to fresh gasoline.

Water contamination is another common issue, especially if your mower was stored in a damp location. Water in the fuel will prevent proper combustion and must be drained before the engine will start.

Inspect the Spark Plug

A faulty spark plug is the second most common reason for starting problems. Remove the spark plug using a spark plug wrench and examine it closely. Look for signs of wear, corrosion, or carbon buildup on the electrode.

If the spark plug appears dirty or corroded, clean it with a wire brush or replace it entirely. A new spark plug typically costs just a few dollars and can make the difference between a mower that starts easily and one that won't start at all.

Check that the spark plug gap matches your engine's specifications, usually found in the owner's manual. An incorrect gap can prevent proper ignition even with a new plug.

Examine the Air Filter

A clogged air filter restricts airflow to the engine, making it difficult or impossible to start. Locate the air filter housing and remove the filter for inspection.

If you have a paper air filter, hold it up to the light. If you can't see light passing through, it needs replacement. Foam filters can often be cleaned with warm soapy water, rinsed thoroughly, and allowed to dry completely before reinstalling.

Never run your mower without an air filter, as this can allow dirt and debris to enter the engine and cause serious damage.

Prime the Engine Properly

Many modern lawnmowers have a primer bulb that helps inject fuel into the carburetor for easier starting. If your mower has a primer bulb, press it firmly 3-5 times before attempting to start the engine.

Over-priming can flood the engine, so avoid pressing the primer bulb more than necessary. If you suspect flooding, wait 15-20 minutes before trying to start the mower again, allowing excess fuel to evaporate.

Check the Oil Level

While low oil won't always prevent starting, many newer mowers have safety features that shut down the engine when oil levels are too low. Pull out the dipstick and check that the oil level falls between the minimum and maximum marks.

If the oil is low, add the appropriate type and amount specified in your owner's manual. If the oil appears black or contains debris, consider changing it completely.

Test the Pull Cord and Recoil System

Sometimes the problem isn't with the engine but with the starting mechanism itself. If the pull cord feels loose or doesn't retract properly, the recoil spring may need adjustment or replacement.

Pull the cord slowly and feel for resistance. The cord should pull smoothly and return to its starting position when released. If it sticks or doesn't retract, you may need to service the recoil assembly.

Look for Clogs in the Fuel Line

Inspect the fuel line running from the gas tank to the carburetor for kinks, cracks, or clogs. A blocked fuel line will prevent gasoline from reaching the engine.

You can often clear minor clogs by disconnecting the fuel line and blowing compressed air through it. Replace any damaged or severely clogged fuel lines.

Consider the Carburetor

If you've checked all the above items and your mower still won't start, the carburetor may need cleaning or adjustment. The carburetor mixes fuel and air in the proper ratio for combustion.

Over time, old fuel can leave deposits that clog the tiny passages in the carburetor. While carburetor cleaning can be more complex, many homeowners can handle basic cleaning with carburetor cleaner spray and compressed air.

Safety Switches and Kill Switches

Modern lawnmowers have various safety features that can prevent starting. Check that the blade engagement lever is in the "off" position and that you're holding the safety handle while pulling the starter cord.

Some mowers also have seat switches or other safety interlocks that must be properly engaged before the engine will start.

When to Call a Professional

If you've worked through this troubleshooting checklist and your mower still won't start, it may be time to consult a small engine repair shop. Complex issues like internal engine problems, carburetor rebuilds, or electrical system faults often require professional expertise and specialized tools.

Preventive Maintenance Tips

To avoid future starting problems, establish a regular maintenance routine. Use fresh fuel with fuel stabilizer, change the oil annually, replace the spark plug each season, and clean or replace the air filter regularly.

Proper storage also prevents many starting issues. Before winter storage, run the mower until the fuel tank is empty or add fuel stabilizer to prevent fuel degradation.

Conclusion

Most lawnmower starting problems have simple solutions that don't require professional repair. By systematically checking the fuel, spark plug, air filter, and other basic components, you can often get your mower running again in just a few minutes.

Remember that regular maintenance prevents most starting issues from occurring in the first place. With proper care and attention, your lawnmower should provide years of reliable service and easy starting every time you need it.