You're all set to mow your lawn, but when you pull the starter cord, your lawn mower won't start. Frustrating, right? It's a common headache many homeowners have faced at one point or another. The good news is, most of the time, it's due to a simple problem you can fix yourself.
In this post, we'll dive into some common reasons why your mower might not be firing up, give you a step-by-step guide on how to troubleshoot, and help you figure out when it’s time to call in the pros. Let's get to the bottom of this and have you mowing in no time!
Why Won't My Lawn Mower Start?
A lawn mower not starting can be caused by many factors, ranging from simple maintenance oversights to more complex mechanical issues. Here are some of the most frequent reasons why your mower may be giving you trouble:
- Out of Fuel or Old Fuel:If your mower is low on gas, it obviously won't start. But even if you have fuel in the tank, old or stale gasoline can cause starting problems. Gasoline sitting for weeks or months can break down and clog up the system.
- Dead or Weak Battery:For electric or battery-powered mowers, a dead or weak battery can prevent your mower from starting.
- Dirty or Clogged Spark Plug:Over time, spark plugs can get dirty or worn out, causing poor ignition or preventing your mower from starting altogether.
- Blocked Air Filter: A clogged air filter can restrict airflow to the engine, making it harder for the mower to start.
- Fuel Line Issues: If there's a problem with the fuel line—whether it's clogged, cracked, or leaking—it can stop fuel from getting to the engine.
- Faulty or Sticking Carburetor:The carburetor mixes air and fuel before it enters the engine. If it's clogged or malfunctioning, your mower won't get the proper fuel mixture, which can make starting difficult.
- Clogged Mower Deck: Grass clippings, dirt, and debris can build up under the mower deck, especially if you've been mowing wet grass. This buildup can block the mower blade from turning properly, which might cause the engine to stall or fail to start.
- Safety Switch Issues:Many lawn mowers have built-in safety switches (such as the blade engagement switch or the handlebar safety switch). If these switches aren't engaged properly, the mower won't start as a safety precaution.
- Flywheel Problems:The flywheel helps spin the engine when you pull the starter cord. If the flywheel is damaged or if its components are rusted, misaligned, or obstructed, it can prevent the engine from turning over, making it impossible to start the mower.
How to Troubleshoot a Lawn Mower That Won't Start?
Now that you know the common reasons why a lawn mower won't start, there are several steps you can take to troubleshoot and possibly fix the problem on your own. Here's how to get your mower up and running again:
Check the Fuel Level and Quality
The first and easiest thing to check is whether you have enough fuel in the tank. If the fuel level looks good and you're wondering, why is my lawn mower turning over but not starting, check whether the fuel is old or contaminated. This is especially likely if you didn't add a fuel stabilizer before storing it for the season.
If the gas has been sitting for more than 30 days, drain it responsibly and refill with fresh gasoline. It might take a few pulls to get the new gas into the carburetor, and you may also need to clean and dry the spark plug a couple of times before it will start working properly again.
Assess the Battery and Electrical Connections
For electric-start mowers, inspect the battery terminals for corrosion and ensure all connections are tight. Clean any corrosion with a mixture of baking soda and water, then dry thoroughly. Use a multimeter to check the battery voltage; if it's below the recommended level, recharge or replace the battery as needed.
Inspect and Replace the Spark Plug
Remove carefully the spark plug wire and use a socket wrench to unscrew the plug. Inspect it for carbon buildup or damage. Clean the plug with brake cleaner if necessary or replace it if worn. Properly reinstall the spark plug, ensuring it's tightened correctly. A functioning spark plug is essential for igniting the fuel-air mixture in the engine.
Examine and Clean the Air Filter
Find the air filter housing, usually positioned near the top or side of the engine. Open the housing and remove the air filter. If it's a foam filter, wash it with mild detergent and water, then allow it to dry completely before lightly oiling and reinstalling. For paper filters, tap them gently to remove debris or replace them if excessively dirty. A clean air filter ensures proper airflow, aiding in engine start-up.
Clear the Vent in the Fuel Cap
Remove the fuel cap and check for a clogged vent. Clean any debris from the vent to allow proper air flow. A clear vent prevents vacuum formation in the fuel tank, which can impede fuel flow to the carburetor. If cleaning doesn't resolve the issue, consider replacing the fuel cap.
Inspect the Fuel Line and Filter
Trace the fuel line from the tank to the carburetor, looking for any signs of cracks, leaks, or blockages. Detach the fuel line carefully and observe if fuel flows freely. If the flow is restricted, the line or filter may be clogged. Clean the fuel line with compressed air and replace the fuel filter if necessary to ensure unobstructed fuel delivery to the engine.
Check and Clean the Carburetor
Check whether the carburetor is clogged with varnish and debris, especially if old fuel has been left in the tank. To clean it, first, turn off the fuel valve or clamp the fuel line to prevent spills. Remove the carburetor from the engine, disassemble it carefully, and use a carburetor cleaner to spray all components, ensuring all passages are clear. Reassemble and reinstall the carburetor, then test the mower.
Clear the Mower Deck
Tip the mower onto its side (following safety precautions) and inspect the underside for grass clippings and debris. Use a trowel to scrape away any buildup, then spray the deck with water to remove the remaining residue. Ensure the deck is completely dry before attempting to start the mower again.
Examine the Safety Interlock System
Inspect the safety interlock systems, such as seat switches or brake levers, to ensure they are functioning correctly. For example, if your mower has a dead man's control (a safety bar that must be held down for the engine to run), ensure the cable connected to it is not damaged or stuck.
If any part of the safety system is faulty, consult your owner's manual for guidance on adjustments or replacements. Properly functioning safety features are crucial for both operation and user protection.
Inspect the Flywheel and Flywheel Key
If the mower blade hits a hard object, the flywheel key can shear, disrupting timing and preventing the engine from starting. To inspect, remove the engine cover to access the flywheel. Use a flywheel puller to remove the flywheel and examine the key for damage. If the key is sheared or damaged, replace it with a new one specified for your mower model. Reassemble the components and attempt to start the engine.
When to Seek Professional Repairs?
Sometimes, despite your best efforts, your lawn mower still won't start. Here's when it's time to call in a professional:
- Persistent Starting Issues:If you've tried all the troubleshooting steps—checking the fuel, spark plug, air filter, and carburetor—and your mower still won't start, it might be a deeper mechanical problem. A professional can inspect and diagnose engine issues that are beyond basic DIY fixes.
- Engine Problems or Strange Noises:Unusual sounds like grinding, knocking, or loud sputtering indicate serious internal engine issues, such as a damaged crankshaft, piston failure, or valve problems.
- Oil Leaks or Smoke:If you notice oil leaks, excessive smoke, or a burning smell coming from the engine, stop using the mower immediately. These are signs of a more serious issue, such as damaged seals or overheating.
- Electrical Failures in Electric-Start Mowers:For electric or battery-powered mowers, electrical failures—such as wiring problems, dead motors, or faulty ignition switches—require expertise.
Conclusion
A lawn mower won't start can really throw a wrench in your day, but the good news is that many of the issues are simple to fix with a little troubleshooting. Now that you've got a better idea of what might be causing the problem, you can start checking things off the list. By following the troubleshooting steps to change the fuel, clear clogs, or replace damaged components, you can systematically identify and resolve the issue. However, if your mower still won't start after all your efforts or shows signs of serious damage, it's best to seek professional help.
FAQ
What should I check first if my lawn mower won't start?
If your lawn mower won't start, you should check first the fuel supply. Make sure that there's enough fresh gasoline in the tank and that the fuel line isn't clogged. If the fuel looks old or contaminated, drain it and refill with fresh gas. Next, inspect the spark plug to see if it's clean and properly connected. A dirty or faulty spark plug can prevent the engine from starting. Also, check the air filter to make sure it's not clogged with debris, as this can restrict airflow and prevent starting.
Why is my mower engine turning over but not starting?
If your mower engine is turning over but not starting, the most likely culprit is a fuel-related issue. The carburetor may be clogged, or the fuel may be stale, preventing proper combustion. Another possibility is a faulty spark plug that's not providing the necessary spark to ignite the fuel. Also, check the choke setting, as an incorrect position can flood the engine or prevent it from getting enough fuel.
Why is my lawn mower not starting after sitting?
When a lawn mower doesn't start after sitting for an extended period, it's often due to stale fuel. Gasoline can degrade over time, especially if it contains ethanol, leading to gum and varnish deposits that block the carburetor and fuel system. To fix this, completely drain the old fuel and replace it with fresh gasoline. You may also need to clean or replace the carburetor if it's severely gummed up. Additionally, check for any fuel line blockages or cracks that may have developed during storage.
