Key Takeaways
- A riding lawn mower that won’t start after sitting can be caused by several issues, including fuel quality, incorrect oil, battery problems, and clogged components.
- Before attempting any repairs, check simple things first, such as the throttle control cable, mower deck, gas cap, and any loose or stuck parts.
- Ensure you use fresh, high-octane gasoline and the correct type of oil for your mower’s engine (four-stroke or two-stroke).
- Check the battery and charge or replace it if necessary.
- Clean or replace the air filter according to the manufacturer’s guidelines.
- If the carburetor is suspected to be the issue, clean it with carburetor cleaner and check for any improvement in starting.
- Inspect the fuel line and filter for clogs, replacing the filter if needed.
- Remove and inspect the spark plug for any dirt, debris, or loose connections.
Table of Contents
A riding lawn mower that won’t start after sitting can be caused by various issues.
In this post we go over some base steps to troubleshoot and fix the problem.
Check the Simple Things First
- Ensure the throttle control cable isn’t compressed or pinched, especially if you fold the handle when not in use.
- Clear any grass clippings and debris from under the mower deck to prevent the blades from bogging down the motor.
- Check the gas cap for clogged breather holes that may impede gas flow.
- Look for loose bolts, rusted or jammed springs, and parts tightened due to rust. Use penetrating lubricant to loosen stuck components.
Check the Fuel Quality
Old, degraded gasoline can cause starting issues, especially if the mower has been sitting all winter. Gasoline with ethanol can separate, leaving water in the fuel tank. To fix this:
- Add fuel stabilizer to the tank to prevent degradation and separation.
- Treat old gas with a product like Iso-Heat.
- Top up the tank with fresh, high-octane gasoline.
Use the Correct Oil
Newer mowers typically have four-stroke engines that require periodic oil changes. Older models may use two-stroke engines that need a fuel-oil mixture. For two-stroke engines:
- Use the manufacturer-recommended two-cycle oil, preferably rated for air-cooled engines.
- Mix the oil and fuel in the proper ratio as specified on the mower.
- Thoroughly blend the oil and gasoline in a separate gas can before adding to the mower.
Check the Battery
Riding mowers often have a 12-volt battery to provide the initial spark. A dead or degraded battery may prevent the mower from starting. To address this:
- Charge the battery on a trickle charge setting the night before use.
- If charging doesn’t help, replace the battery with a new one from a hardware store.
Clean the Air Filter
A clogged air filter can restrict air flow to the spark plug. Clean or replace the air filter according to the manufacturer’s guidelines.
If the air filter is the issue, then they are pretty cheap online.
Inspect the Carburetor
A gummed-up carburetor can make starting difficult. To check if the carburetor is the issue:
- Ensure there’s gas in the tank, the fuel valve is on, and the spark plug is good.
- Spray a one-second burst of carburetor cleaner into the carburetor throat.
- Engage the handle control and pull the cord several times.
- If the engine sputters and dies, it’s likely a fuel problem. If it doesn’t start at all, the issue may be the carburetor or spark plug.
Check the Fuel Line and Filter
If the engine starts briefly then dies, check the fuel line and filter for clogs. Replace the fuel filter if necessary, following these steps:
- Locate the filter inside the fuel tank or attached to the fuel line.
- Drain the gas tank if the filter is inside.
- Remove the old filter and clean any residue from the housing.
- Install the new filter, ensuring the metal clips are securely connected.
- Check for leaks before using the mower.
Inspect the Spark Plug
A dirty or loose spark plug can prevent the engine from starting. Remove and inspect the spark plug for any issues.
By systematically addressing these common problems, you can often get your riding mower running again without the need for professional service.
FAQ
References
From his childhood obsession with gardening to the decade he spent operating a hobby farm, Eric has developed over four decades of experience in self-sufficiency. Not only does this include the organic elements of growing and tending plants, but it also includes a wealth of experience in lawn care, landscaping, and gardening equipment.