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Why does my hedge trimmer stall on start-up or choke on acceleration?

If you’ve ever owned a hedge trimmer, especially a petrol hedge trimmer, you’ve probably asked yourself this question: Why does my hedge trimmer jam or stop? Luckily for you, I’ve taken the time to try and understand why a hedge trimmer can stall, and I’ve written about it in this article.

As all hedge trimmer users know, these tools are not easy to use. It takes time to learn how to use them properly… and even more time to figure out how to solve complex problems like this one!

Carburetor problem

Adjusting screw

You may be wondering why your hedge trimmer chokes on acceleration or stalls when starting. It’s probably because the carburettor is set at the factory and you need to adjust it. This is usually caused by incorrect adjustment of the richness screw.

To solve this problem, follow the steps below:

Locate the adjustment screw (richness screw) on the side of your carburettor – it’s usually hidden in a recess that’s hard to reach. You’ll need a small flat head screwdriver for this job!

Start your bike and pour some fuel into the tank. Gradually close the richness screw as you accelerate and release the throttle. You’ll notice that it takes less time to accelerate than before because you’re putting less fuel into the engine.

If you’ve closed the richness screw too far, you’ll find that the engine stalls when you accelerate. Open the enrichment screw slightly and restart your machine. Then open the screw slowly and test acceleration by opening and closing it a little at a time until you find the perfect setting.

Excess fuel

You’ve cleaned the carburettor and probably dismantled a good part of it. Choke on acceleration can be caused by a lack of fuel, it’s true. But it can also, and often is, caused by too much fuel.

When you start your hedge trimmer, there’s a compression element in the system that pushes fuel back into the carburettor. This has to happen for your hedge trimmer to start and run smoothly. But if there’s too much fuel in the system, it will overflow and stop your hedge trimmer.

Remember, if your hedge trimmer stalls when starting or stalls when accelerating, try draining some fuel from the tank before trying again.

Lack of fuel

The second thing to check is whether your hedge trimmer is experiencing any resistance when starting. If it’s not getting enough fuel from the tank, it may stall or choke on acceleration. If this happens, make sure there’s enough fuel in the tank and that there are no kinks or other obstructions in the fuel line from the tank to the engine.

Hose problem

We’d like to help you answer the question of why your hedge trimmer stalls when starting or stalls when accelerating. After checking the carburettor, let’s check that the hoses are in good condition. It’s sometimes easy to overlook a micro-crack that allows air to enter. If this is the case, there’s a good chance that the diaphragm is also damaged.

Fuel cap problem

We’re sorry you’re still having problems with your hedge trimmer. Here’s one more thing to check before you call for help:

Check the reservoir cap. There’s an air inlet on the cap that doesn’t allow the reservoir to be pressurized. If this inlet allows air to pass through, or if the tank is not properly connected, the motor will have problems and stall.

Reservoir strainer problem

There are several reasons why your hedge trimmer may stall or choke on acceleration.

Another thing to check is the grass catcher. It may be clogged with debris, which can cause your hedge trimmer to stall when you try to accelerate. If this is the case, it should be possible to clean it without removing the entire tank – consult your user manual or call your hedge trimmer brand’s customer service department for more information on how to do this.

Spark plug and/or coil problem

Hedge trimmers can stall when starting or choke when accelerating due to a dry spark plug or flooded engine.

The spark plug is the part that ignites the fuel in your engine, so if it’s dry, you won’t have any power to start your hedge trimmer. To solve this problem, simply inject a little petrol into the spark plug hole and try again.

If your hedge trimmer still won’t start easily with a wet spark plug, check that there is no debris in the fuel tank. If there is, remove it with an old toothbrush, taking care not to scratch the metal parts of the engine!

If your hedge trimmer stalls when starting or chokes on acceleration, the second thing to check is the coil. The coil feeds the spark plug, so if it’s not working properly it could be causing these problems.

To check the coil: remove the spark plug and leave it inserted. Connect it to the engine and try to start it (wearing gloves!). If you get a spark, the coil and spark plug are in good condition.

Piston problem

I’m here to answer your question about why your hedge trimmer stalls when starting or stalls when accelerating.

First of all, I’d advise you to remove the muffler and check that the piston is not scratched. If it is scratched, it means that your mixture is too old or too little.

If you still have problems with your hedge trimmer, don’t hesitate to contact the manufacturer’s after-sales service.

Priming pump problem

The engine won’t start, the hedge trimmer stalls when starting or stutters when accelerating.

If none of the above is the cause of your problem, check that the priming pump is full; if so, a simple carburettor adjustment may help.

Check muffler and tailpipe

First, check the exhaust outlet, clean the piston at the bottom, remove the spark plug, manoeuvre by hand to extract the particles and then add a few drops of engine oil into the cylinder.

Then check the exhaust pipe; if it’s clogged with grass or debris, clean it and reassemble it. If you’re still having problems, check your spark plug again. If all else fails, take it to an authorised workshop for repair!

Quentin Terra Garden
About the author: Quentin, passionate gardener

Founder of the blog dedicated to gardening tools and advice since 2021, I’m Quentin, a gardening enthusiast. My aim is to share practical information and recommendations based on my experience. Join me to explore the world of gardening, try out new tools and share our passion for nature.