Why Does My Petrol Lawn Mower Keep Cutting Out?

While there’s nothing quite as frustrating as a petrol lawn mower that keeps cutting out, resist the urge to give your machine a good kick…at least for now. Instead, follow these troubleshooting steps and you should have your mower running well again in no time. 

Take a Look at the Blades

Some petrol lawn mowers will cut out when they’re used on wet grass. This is due to a lack of power – wet grass is much heavier. It’s also more likely to stick to the blades, which puts too much pressure on the engine. 

Take a look at your mower’s blades. If they’ve covered in built-up grass, then chances are that the grass was overly wet when you cut it. Try again once it’s dry – your lawn mower should run without any problems. 

If the blades are worn down, they may also be putting too much strain on the engine, causing it to cut out. You can sharpen mower blades at home if you have the right tools.

Not sure if the blades are blunt? Take a look at our page on sharpening mower blades to see if yours need attention.

Check the Spark Plug 

If your lawn mower runs for several minutes before cutting out, then the first place to look is the spark plug. Give it a clean or replace it with a new one and see if this helps. You might also need to clean or replace the carburettor. 

Replace the Petrol 

If your mower cuts out soon after starting up, or struggles to even start in the first place, stale petrol could be the culprit. After petrol has been sitting in a lawn mower for a while (2 – 3 months), it starts to evaporate, leaving behind a residue that causes clogs and restricts petrol flow. 

You’ll need to remove all of the stale petrol from your lawn mower and replace it with fresh fuel. 

Drain Out Some Oil 

If you were over-enthusiastic when pouring oil into your lawn mower, the result will be white smoke coming from the engine plus the engine cutting out soon after you get it running. 

Use the dipstick in the oil cap to check your oil level, draining away any excess.

If you’re curious about which oil to use in your mower, you’ll find a wealth of information in our article about engine oil.

Check the Carburettor 

If your lawn mower starts but then quickly cuts out, it’s worth checking the carburettor. If this is dirty or clogged, your lawn mower’s engine won’t be able to run for very long after it has been started. 

The best way to clean your carburettor is by purchasing a carburettor cleaner. However, if it looks as though your carburettor is beyond cleaning, it may be time for a new one. 

We’ve written an in-depth guide to servicing a petrol lawn mower, where we’ve covered this process in more detail – it might be a useful read at this stage!

Clear the Air Filter 

Does your lawn mower only cut out when you’re working in long grass? If so, a clogged air filter could be to blame. Long grass and other debris can sometimes block the air flow to the engine of a lawn mower, which is what causes it to cut out. 

Give the filter a tap to dislodge any large pieces of dirt, and make an effort to clean it on a regular basis. If you’re not sure where to find the air filter, take a look at our page on cleaning your petrol mower.

What Next? 

If you’ve tried all of the above and your lawn mower is still cutting out, it’s time to turn to a professional. There are a few other issues that could be at play here, from a faulty choke to a blockage in the fuel line – these more complex matters are best left to the experts. 

Don’t forget to check your lawn mower’s warranty before calling your local repair centre – you never know, the manufacturer may cover the cost of any repairs!

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