How To Fix A Weed Eater That Won’t Start

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As with any form of machinery, Weed Eaters are subject to mechanical failures and all manner of problems, and as such it is important to know what to do when such a problem rears its ugly head. 

The most common problem has to be a failure to switch on, but what exactly is the cause of a problem like this, and what can be done to remedy it?

What Is A Weed Eater? 

Designed for trimming the edging of lawns, and other pesky areas where weeds and long grass might grow, Weed Eaters are designed to go where lawn mowers cannot, and to grant you a degree of control and perfection that would have otherwise been impossible to achieve. 

Why Won’t Your Weed Eater Start? 

Failure to start is a common problem with many handheld pieces of machinery like this, and there are naturally several reasons why this might have occurred. 


If your Weed Eater is a gas powered model, then it could potentially be an issue with the gasoline. 

This could be down to an insufficient amount of fuel in the tank, or it could be something more serious like the fuel having degraded or spoiled within the tank – something that could have occurred if the machine has been sat with a full tank for a long period of time. 

The problem could also be the ratio of gas to oil, and if this is the case then you might need to amend these ratios, or empty them completely and refill them. 


  • Check there is enough gas – top up if not 
  • If gas has separated, shake machine to mix it up
  • If the gas is old, then empty the fuel tank, and refill with the recommended ratio of oil and gas

Air Filter 

One of the main reasons that lawn mowers and trimmers break is because their air filters become clogged with dust, dirt, and debris. You have to think that, during use, these machines pick up a lot of detritus. 

This is why proper maintenance is required, and by simply changing your air filters – or cleaning them – regularly, you can avoid more headaches down the road. 


  • Located air filter box at rear of Weed Eater, and remove it
  • Brush off the air filter if the dirt is minor
  • Wash with detergent (or other cleaning fluids) if extensive
  • Let the filter dry once more
  • Reattach and fasten the box back on

Spark Plugs

The spark plug could also be the issue. These are what ignite the engine and let the whole thing tick over properly, and if these have become damaged or dirty, then it can be detrimental to the machine in general. 


  • Remove the cover and take out the plug
  • Gently clean the spark plug, removing all grime and debris
  • Check for cracks – these will require a replacement if present
  • Use proper tools – such as spark plug cleaning tools
  • Ensure plug nodule gap is around .025 – .030, and adjust where necessary
  • Reattach plug and cover

Ignition Coil

The ignition coil is inside the trigger handle, and is responsible for sending electronic signals to the engine and allowing it to start up. 

These are unfortunately one of the most fragile parts of the entire machine, and after periods of extensive use they can become worn out and damaged. If everything else is working, then this could be the source of your woes. 


  • Insert spark plug wire into spark tester
  • Attach alligator clips to metallic end of plug
  • Turn ignition on, and monitor through the window
  • Strong, blue sparks indicate healthy ignition switch coil
  • Little to no spark means it needs replacing


The carburetor is another important part of the engine, and if these become dirty or damaged, then your engine is unlikely to start. 

As such, proper cleaning and maintenance is the best way to avoid these becoming damaged over time. 


  • Remove fuel filter and clean with solvent cleaner
  • Allow time for solution to dissolve debris and grime
  • Reattach and secure
  • If worn out, then carburetor needs replacing

Spark Arrestor Screen

These screens are essentially filters that limit the size of the particles that can be expelled from the engine exhaust. These are important, and stop sparks emanating from the engine and causing a fire. 

When these are damaged, they can cause slower speed, lagging engine, or a failure to start. 


  • Remove spark arrestor screen and use butane torch to burn off any carbon that might have become crusted onto the inside
  • Let it cool and then clean further with a sturdy brush
  • Reattach and secure

Flooded Engine

Repeatedly trying to turn the Weed Eater on, or turning it over onto each side, can cause the engine to become flooded – thus stopping it from turning on. 


  • Turn off switch to on
  • Rev the ignition switch to burn fuel away
  • Continue until black smoke fades
  • Allow it to rest and cool down before using again


Of course, if it is not something mechanical or chemical, then it can only be electrical. If your Weed Eater doesn’t start, then it could be a sign of an electrical fault, or a faulty battery – and if so these will need replacing. 


  • Ensure everything is connected and plugged in
  • Ensure electrical outlet is drawing power
  • Check all the fuses and extensions
  • Check circuit breakers
  • Make sure the settings are correct

Final Thoughts

And there we have it, everything you need to know about Weed Eater products, and the best ways to fix them if they refuse to start.

It’s true that Weed Eater products make gardening a lot easier, and make some of the harder tasks a lot simpler and less time consuming. However, as with anything, without sufficient maintenance, things can soon go to rack and ruin. 

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