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Lawn Mower Will Not Start After Running Out Of Petrol - Here's What Could Be Why?

Written by William
Last Updated on January 24, 2023

Why Is My Lawnmower Not Starting After Running Out Of Fuel?

Due to lawnmowers not having a fuel gauge, they can easily run of fuel before you know it, this isn't typically an issue as your mower can just be refilled, however, what do you do when your mower won't start again?

If your mower is giving you start-up issues after you run out of fuel, it could be due to many potential causes such as; a dirty or bad carburettor, damaged choke, faulty coil or old gas. 

To help you troubleshoot and figure out what's causing no start-up issue in your mower, we have listed out the common causes that could be affecting your mower and how to fix them below.

Common Causes As To Why Your Mower Is Not Starting After Running Out Of Fuel

When a lawnmower does not restart after running out of gas, most of the time the cause is a dirty carburettor bowl, as its sucking up any debris which is at the bottom of your mower due to it running out of fuel.

However, there is the potential for some other coincidences to occur that could be causing this issue.

We have listed these issues and their solutions below.

A Dirty/Faulty Carburettor

If your lawnmower is not starting after running out of petrol, then one of the first causes you should troubleshoot is the carburettor.

When your mower runs out of fuel it will be sucking the debris and dirt that is sitting in the bottom of your tank, not everything will be caught by the gas filter in your mower, causing issues like this when you run out of fuel.


The solution to this is to simply clean your mowers carburettor bowl, you can do this by draining the bowl which is located behind your lawnmowers air filter.

This fuel bowl is where you will find the dirt that has made it past the filter on your mower, you can drain it by using the drain bolt if your mower has one.

If this cleaning method does not work, then you may simply just have a failed carburettor that needs replacing so your mower can start-up again.

There Is An Air Lock

One of the other most common causes as to why your mower is starting up after running out of fuel is an airlock in the fuel system.

An airlock can occur in your mower when your machine runs out of fuel as the lines are filled with air instead of petrol. As you refill your mower, this could push the gas towards your mower's carburettor and block the new gas from getting to the engine of your mower.


To fix this, make sure your mower's tank is filled right to the top with gas or use the carburettor bowl draining method above, this draining should help release the airlock in the carburettor on top.

Your Choke Is Not Working

On many mowers nowadays there is an auto choke function, this auto choke has the potential to flood your mower's engine if it sticks in the on position and can cause starting issues with your mower.

This is not directly related to running out of fuel but could be a potential coincidence as to why your lawnmower is not starting.


Firstly, you should determine if your mowers choke is working the way it should be by removing the air filter while the mower is hot and seeing if the choke plate is closed, which is an indication something is wrong if it is.

You may need to replace/repair the auto choke if you find it is giving your mower issues.

Bad Fuel

Another reason why your mower might not be starting in this situation is bad gas.

If you have recently filled your mower with old petrol then you know why your lawnmower is not starting, as fuel starts to degrade after just 30 days.


Drain the bad fuel from your mower and replace it with fresh instead, try using a stabiliser next time to prevent your petrol from going bad so quickly and avoid using old fuel.

Other Reasons As To Why Your Lawnmower Is Not Running

Now we have covered the most common causes that can explain why your mower is not starting after running out of fuel, you should also consider a few other reasons that could be stopping your mower from running, just in case these steps above don't work.

These issues below may not be directly related to running out of fuel but could happen at the same time as your mower runs out of fuel, preventing it from starting back up again or shutting down quickly.

Tall Grass

When mowing through very tall grass your lawnmower may get clogged and stop running, even when you try to turn it back on, this can happen if your lawnmower has a lower cutting height than the grass itself.

Smaller engine mowers may also not be suitable for tall thick grass and can prevent the mower from starting up when under strain.

To fix this simply adjust the cutting height on your mower or use an appropriate model for tougher and taller grass in the future.

Dirty Spark Plug

A dirty spark plug can be a reason why your mower is not restarting, if your spark plug is not in the right position or dirty, then you will need to clean and reposition it.

You may have to replace the whole spark plug which can fix the problem easily too.

Low Oil

Oil top-up is a requirement on your lawnmower and can cause an issue if the oil level is allowed to become too low, however, this problem can be easily fixed as topping up the oil should help to start up the mower again.

Bad Blades

Very dull blades could potentially stop your mower from running, this problem is more of a coincidence but can be solved by simply sharpening or replacing your blades, then your mower should be working as brand new again.

Damaged blades or unbalanced blades will additionally need to be replaced or refitted to allow your mower to function again correctly.

Frequently Asked Questions About Why Your Lawnmower Is Not Starting After Running Out Of Petrol

What safety precautions should I follow before checking my mower? 

Always disconnect the spark plug and tip your mower the right way when checking it to avoid any gas and oil leaks occurring.

You should always wear gloves when handling and checking the blades of your mower, as well as removing any sources of ignition as the gas is highly flammable.

Why is my fuel reaching my engine so slowly? 

This could be due to an airlock as we mentioned above or a dirty carburettor bowl/filter, both can be easily fixed by draining the carburettor bowl as we mentioned above.

How do I check the spark plug on my mower? 

You can test to see if the spark plug on your mower is working by replacing it with another and seeing it works, also closely inspect your plug for any signs of damage or corrosion that could be causing issues.

Last Words

Overall, if your lawnmower is not starting after it runs out of fuel then most likely, it's due to there being an airlock or debris at the bottom of your carburettor, luckily, both can be fixed easily by draining the bowl.

If this does not fix your mower, then the other reasons above could also be giving potential start-up issues and maybe a coincidence.

About the author
Written by William
I have always had a passion for gardening and that with a background in selling lawn mowers for the past 10 years, I have become very knowledgeable in all types of gardening tools. The site was created as a hub where I can review and write about all of the tips around gardening.
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