Why My Lawn Mower Won’t Start After Sitting? Easy Fixes

There are several reasons why your lawn mower might not start after remaining idle for an extended period. Some of the most common issues include fuel-related problems, spark plug issues, and problems with the carburetor.

In this comprehensive guide, we’ll explain these issues in detail, discuss their possible causes and symptoms, and provide clear instructions on troubleshooting them. Let’s jump right in.

What Causes A Lawnmower Won’t To Not Start After Sitting?

When spring arrives, many people realize that their lawnmowers may have been neglected and left to sit during the colder months. Unfortunately, this can lead to a lawnmower not starting despite all efforts.

There are numerous reasons why a lawn mover won’t start after sitting idle for a while, so let’s look into some common ones. It is essential to remember that protective gear must be worn when performing any maintenance on a lawn mower and that safety measures must be taken if any warnings appear. Additionally, caution should always be exercised when dealing with sharp blades or engine components. Let’s understand it:

1. Your Mower Runs Out Of Gas Or Gas is Too Old

If your gas-powered lawn mower isn’t performing as expected, you may have to consider the fuel. Without gas, the lawnmower can’t run – so if there’s none in the tank, fill it up! But if the gas has been sitting there for over a month, it’s considered too old and will need replacing.

Draining all the fuel is essential before filling it with fresh gasoline. Cleaning the fuel tank and bowl are necessary steps to ensure that no old residue remains. After completing this process, you can refill with new gas.

TrueFuel is an excellent choice for anyone looking to purchase some fuel. You will find it at your local hardware store, which contains no ethanol. The advantage of TrueFuel is that it runs clean and never gets old, so you don’t have to worry about draining the gas tank every time you use the mower. Although it may be more expensive than regular gasoline, this healthier option will help your machine last longer in the long run.

If you do not use your lawn mower often, adding a fuel stabilizer can keep the freshness of the gasoline for up to two years. However, make sure that you only add a stabilizer to the new gas — if applied to the old gas, it will stop it from worsening but not restore its original freshness.

Sta-Bil fuel stabilizer is an excellent choice due to its effectiveness with all types of gasoline and its corrosion prevention in fuel tanks. Plus, it can be safely used in any engine that takes gasoline.

2. Proper Check The Carburetor 

Keeping your lawn mower’s carburetor clean is essential, whether you use it regularly or occasionally. Failure to do so could result in a faulty engine, a corroded carburetor, and frequent parts replacement. A practical solution is to use a carburetor cleaner spray which can easily be purchased at an affordable price.

To begin cleaning the dirty carburetor, remove the air filter and spray it with the cleaner. Allow time for the grime and dirt to break down before wiping them off with a clean cloth. If your carburetor has a float bowl, make sure this gets cleaned by emptying fuel from the drain plug and then using the spray.

The spray may not always work well enough to clear all the dirt, so you should take your carburetor apart and give it a deeper clean.

When disassembling your carburetor, be extra careful when reassembling it as an incorrect installation could cause gas leakage, which is not ideal. Properly cleaning your lawn mower’s carburetor will help maintain its performance and ensure it lasts many years.

3. Inspect The Spark Plug

Replacing a faulty spark plug is one of the most cost-effective lawn mower parts and can be done quite quickly. Before beginning, ensure the engine is cool and remove the wire from the spark plug. Clean off any dust or dirt, and rust from metal parts. Use a socket wrench to unscrew the old spark plug and replace it with a new one–it should be firm but not too tight.

Reattach the spark wire and test out the engine. It’s essential to check for signs of corrosion or discoloration at the end of the spark plug that fits into the mower; if so, definitely replace it! If there’s a dry deposit around electrodes or the fuel-to-air ratio appears imbalanced, it could suggest the engine seal is broken. Spark plugs often break first and require replacement; however, if you feel an excellent clean might do the trick, try it! When all else fails, go ahead and get yourself a new one.

If the spark plug of your lawn mower is faulty, you can easily remove it using a wrench and wiping away any black deposits with a clean cloth. Brown deposits are normal and not to worry about.

Once the spark plug is back in the socket, ensure it’s firmly connected so it won’t come loose. On the other hand, if you find a fuel leak causing wetness on your spark plug, you must seek professional assistance for servicing and investigation.

Before conducting any type of lawn mower maintenance or repairs, be sure to remove the spark plugs to avoid accidental starts permanently. If you feel like it’s not good enough even after cleaning, just go ahead and buy a new one.

4. Check The Main Jet

The main jet of your lawn mower is an essential component for it to run correctly. Remove the spark plug cap and shut off the fuel valve to ensure its cleanliness. Then, drain the fuel tank and inspect it for any dirt or old gas.

If blockages are detected in the main jet, use carburetor spray and insert a wire to clear them out if necessary. Once done, give another spray of cleaner before proceeding further.

It should be noted that for most lawnmowers, fuel passes through the main jet into the carburetor and combustion chamber; thus, cleaning or changing these parts should be prioritized if they require attention so that your mower can start up without any issues.

5. Change The Oil

Checking the oil in your mower is just as important as having enough fuel to make it run. Pay attention to its quality, any residue present, and if there’s enough. Small engines power most mowers, so they don’t require much lubricant.

To determine whether or not an oil change is necessary, start by cleaning the area around the fuel cap on the crankcase before opening it up. Then inspect using a clean cloth or dipstick.

When changing the oil, remove the spark plug first, then locate and unscrew the drain plug. Place a pan or newspaper beneath the mower and tilt it sideways so that all of the old oil drains out. Make sure that no dirt or debris goes into the crankcase.

Once all of the oil has been drained, replace the drain plug tightly; it’s essential that no new oil leaks out. Find out what oil is needed for your specific mower by consulting its owner’s manual and then filling it out accordingly. Make sure to test it for any possible leaks by running it briefly.

6. Check The Air Filter

A steady flow of oxygen is essential for a lawnmower to run optimally. A clogged intake filter can significantly affect the performance of your mower and even prevent it from starting up altogether.

There are two types of air filters for lawnmowers: foam only and dual element. The foam filter traps dirt particles when motor oil is used and should be cleaned every three months. This air filter also serves as a guard to prevent debris and dust from entering the engine’s inner workings. If left uncleaned for too long, it will impede the engine’s functioning, rendering the mower inoperable.

To ensure optimal usage, clean or replace your air filter regularly- say after every 25 hours. The methods for pushing and riding lawnmowers may vary, so consult the user manual to discover the best way to replace a clogged intake filter.

To change out the foam filter, remove the screw and old filter first. Then discard the old one and clean up the area before inserting a new one. After that, soak the new filter in fresh oil and wipe away any excess with a cloth. Then, you can reassemble the filter and reinstall the carburetor.

Regarding dual filters, remove the knob first and then use foam pre-cleaner on the filter. If it’s too worn out or full of dirt, better to replace it instead. Dirt won’t hesitate to pass through even the slightest crannies or holes, so replacing a filter is always the safest option.

7. Check The Brake Cable

If your lawnmower refuses to start, it could be because the brake cable is too loose. You can test this theory by holding the brake handle and pulling on the cable – if there’s any given present, you’ll know it needs tightening.

To determine whether this is the cause of your mower’s starting issues, try starting it while keeping the cable tight. If it starts, you’ll know the brake cable is the problem. Adjusting it can be quickly done using a crescent wrench and some vice grips.

8. Inspect The Flywheel Key

The flywheel key in mowers is the wheel that begins spinning when you start it. If a solid object like a stone impacts it with full power, this could lead to a broken flywheel key, which will stop the lawnmower from starting when you pull the cord.

To assess if the flywheel key is the problem, you must first remove it from your mower. This can be challenging as the nut that keeps it in place inside the mower is usually very tight, but to loosen and remove it, you must ensure it is immobile.

9. Clean Out The Mower Deck

The mowing deck is where grass clippings are usually collected as the lawnmower works through your garden. These clippings can easily clog the deck without regular cleaning, especially when mowing wet grass. A blocked mowing deck will stop the lawnmower blade from turning. Signs that this has happened include a starter rope that’s hard to pull or seems to be stuck.

To sort out the clog, place the mower on its side and carefully inspect it underneath. If you have a riding mower, it’s best to avoid this step altogether. Use a trowel to eliminate any clumps of grass clippings and prevent future blockages by cleaning your mower after every use.

How To Recheck Your Lawnmower Starts After Sitting?

  1. Safe Storage: If your lawnmower isn’t used for a while, such as through winter, you must ensure it’s stored in a safe spot to protect it from harsh weather. An ideal place would be inside a garage or shed, away from any furnaces and water heaters.
  2. Use Without Ethanol Gas: Ethanol is known to damage carburetors in small motors over time. While gas without ethanol may be more expensive, it’s worth spending the extra money as this will save you from buying new parts or taking regular trips to a lawnmower mechanic.
  3. Professional Lawn Maintenance: While there are many tasks, we can do ourselves when it comes to maintaining our lawnmowers, getting annual servicing and major repairs done by a professional is best for the long-term health of your machine. This may incur additional costs, but it’s an investment that will extend its life span and keep you away from buying a new one for years.
  4. Preventive Maintenance Tips: To avoid similar problems in the future, follow these expert tips for maintaining your lawn mower:
  • Store your lawn mower in a dry, well-ventilated area to prevent corrosion and water contamination.
  • Drain or stabilize the fuel during extended periods of inactivity. Use a fuel stabilizer when storing your mower for more than 30 days.
  • Replace the spark plug as the manufacturer recommends, typically every 100 hours of mower use or annually.
  • Clean the carburetor regularly to prevent buildup and blockage.
  • Remember to follow the mower manufacturer’s specific maintenance guidelines.

By following these troubleshooting steps and maintaining your lawn mower properly, you should be able to keep it in optimal working condition, ensuring a quick start every time you need it.

Related FAQs

Why My Briggs and Stratton Lawn Mower won t start after sitting?

If your Briggs & Stratton lawn mower isn’t starting up correctly after being inactive for some time, there could be several reasons behind it: from running out of gas to needing an engine oil change, from having clogged air filters or carburetors to disconnected spark plugs. All these issues should be inspected to solve the problem.

Why won t my lawn mower start after sitting for a long time?

After sitting idle for a while, a lawn mower can develop some issues preventing it from starting. One common problem is the buildup of dirt, debris, and oil in the carburetor. Another issue can be a dead battery or spark plug.

Why does my lawn mower take forever to start?

The carburetor float bowl may contain old or bad fuel that has evaporated over time, leaving behind a thick and sticky substance. This can clog the carburetor, making it hard to start the engine. To solve this problem, use a carburetor cleaner to clean the blockage.


Lawn mower won’t start after sitting for a while can be a common problem. To prevent this, it’s essential to maintain and store the lawn mower correctly.

This includes draining or stabilizing fuel during extended periods of inactivity, replacing spark plugs, and cleaning carburetors regularly. If your lawnmower doesn’t start after sitting, inspect the brake cable, flywheel key, and mower deck and check for clogs.

Lastly, having annual servicing done by a professional is recommended to keep the lawn mower in optimal working condition.

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