Lawn Mower Won’t Start After Sitting? (Briggs and Stratton Fixes)

Lawnmowers are commonly deployed when the grass is actively growing. These machines usually idle in a garage or shed during winter and severe drought. If you did not prepare well before storage, you’d have problems starting the mower.

A lawn mower may not start after sitting due to dirty or air filters, insufficient or bad fuel, damaged or foul spark plugs, a clogged carburetor, or a flat battery.

CAUTION: Fix your lawn mower in a well-ventilated area. Stale fuel can spew toxic fumes. Always disconnect the spark plug cable to prevent the engine from accidentally starting.

Why Lawn Mower Won’t Start After Sitting

The following are reasons why a lawn mower won’t start after sitting idle for many weeks and possible fixes.

1. Fuel problem

Fuel is needed to power a gas lawn mower engine. The engine will not start when out of gas, the fuel has gone bad, or there is a clog in the fuel line. Unused gas left in a lawn mower over the winter can get stale, gum up parts and invite rust. This is the reason why fuel should be stabilized when winterizing a lawn mower.

How to Fix

To be sure that fuel is the problem, see if there is any fuel in the tank. Next, if you did not stabilize the remaining fuel before storage, you have to drain it and add a new one. Then try to start the engine. If nothing happens, try the next hack.

2. Bad engine oil

Engine oil is helpful in lubricating moving parts in the engine. After long storage, engine oil may go bad or gum up. This will definitely lead to problems starting your engine.

How to Fix

To inspect this, use the provided dipstick to check if the available engine oil in the crankcase is enough and if it’s in a good state. How often to change your lawn mowers engine oil may depend on the manufacturer’s recommended hours of runtime or the lawn conditions.

Ideally, change the oil in your brand-new lawn mower’s first 5 hours of operation. For your existing push lawn mower, do it after every 40 to 50 hours of run time. Tractors and riding lawn mower engine oil need to be changed at the start of every season.

3. Clogged carburetor

A carburetor helps mix air and fuel before being channeled into the ignition chamber of the engine. Sometimes dirt and debris can end up in the carburetor when the air filters are clogged or damaged. Lawn mower not starting is one of the signs of a troubled carburetor.

How to Fix

To solve this problem, remove the lawn mower casing and the air filter. You will then be able to access the carburetor, Clean your lawn mowers carburetor and fuel lines. Replace the rusty bowl and its nut, pin, and floating gasket.

4. Corroded or disconnected spark plugs

Spark plugs ignite the air/fuel mixture to create an explosion that makes an engine produce power. During the long storage of your mower, spark plugs can get corroded or disconnected from their socket. It is obvious that your engine will not start without the proper functioning of the spark plugs.

How to Fix

To fix this problem, install a new spark plug for your lawn mower type. Once you locate the plugs, simply use the spark plug socket wrench to remove the old plug and install the new one. Tighten the plug but don’t overdo it to the point of causing damage.

5. Damaged or clogged air filter

Air filters clean the air to remove debris before it’s allowed to mix with fuel in the carburetor. A damaged or clogged air filter can lead to several problems in a lawn mower engine, including not starting, burning rich fuel, and sputtering.

How to Fix

If you suspect the air filter is why your lawn mower is not starting, then you should replace or clean it as directed in the user manual. Briggs and Stratton lawn mower air filters are affordable, and you can get them in nearby hardware or order them online.

6. Battery problem

If your lawn mower relies on battery power to ignite the engine, then there is a chance that your lawn mower battery is flat or the terminals are corroded. This usually happens when you forget to remove the battery before the long storage of your lawn mower.

How to fix

Simply remove the lawn mower battery and clean its terminals using a wire brush. Check the level of water and top it up where necessary. Recharge the battery and connect it back, then try to start the engine again.

How to Prepare your Lawn Mower for Storage

As part of winterizing, the following are important things before storage of your lawn mower.

Use fuel stabilizer

Some resources will tell you to drain gas from a lawn mower for winter storage. We found this to be inappropriate. An empty fuel tank is open to condensation. Water droplets may form and corrode the tank and fuel lines.

You need to fill the fuel tank to about 95% with stabilized fuel. Then run the engine for about 5 to 10 minutes so the stabilized fuel can work in the fuel line. This additive will stop any chemical reaction or breakdown of the fuel from happening.

Change engine oil

Your lawn mower has been working during the entire mowing season. By now, the engine oil is now dirty and worn out. This old oil can gum up or go bad if stored with your lawn mower for longer.

For everything to start off well the next season, drain the oil from your lawn mower and add a fresh one. Be sure to use a dipstick to avoid adding less or excess engine oil.

Remove the battery

Remove a battery from your lawn mower before storing it. Clean the terminals with a wire brush to remove any corrosion. Use a cloth on the casing with soapy water and dry it with another piece of cloth. Store the battery indoors, away from heat, gas cylinders and water.

Change air filters

Before storing your lawn mower for winter, replace the old air filters. By now, the current air filters are clogged or worn out. New or clean air filters will ensure that your engine starts well when you start your lawn mower in the coming season.

Replace spark plugs

This will be the ideal time to replace your mower’s spark plugs with new ones. Storing it with the current worn-out plugs may make it difficult to start your lawn mower after sitting for a long. Cleaning the oxidation layer may be an option if you recently replaced them.

Clean the mower

Disconnect spark plugs and hose your lawn mower to remove grass, leaves, and mud. Let it dry completely before storing it in a clean, dry place. Your garage, warehouse, or shed are the ideal places to store your lawn mower.

Final Thought

We have seen what can make your lawn mower not start after sitting and how to fix it. You can avoid the problem by adequately preparing your lawn mower for storage as directed in this guide or by the manufacturers.

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