8 Reasons Why Your Weed Eater Wont Start (2022)

A weed eater is an important gardening tool that makes it easy to trim and maintain your lawn. The problem is that sometimes your weed eater wont start simply.

Imagine trying to start your trimmer after a long store-away or sometimes even after you just used it the day before and it refuses to crank. Unfortunately, this is a very common issue that happens to almost all owners at least once. So, what are you going to do? Trim your weeds with a scythe? Well before you get out that sometimes almost impossible to use scythe or pack your weed eater up to the store, have a look at our list of common problems that can cause weed eater malfunctions.

Common Reasons Why Weed Eater Wont Start: Issues and How to Solve them

If your weed eater isn’t starting it could be:

  • Gasoline problem
  • Dirty air filter
  • Faulty spark plug
  • Faulty Ignition coil
  • Malfunctioning carburetor
  • Dirty spark arrestor
  • Flooded Engine
  • Electrical or battery malfunctions

1) Gasoline Related Problems

Gasoline Related Problems weed eater

This is the major problem that could cause a weed eater to malfunction. Sometimes it’s because:

  • The gas tank is empty or almost empty.
  • The gas is old. Oxygen can break down unstabilized ethanol-containing gas in under a month.
  • Using the incorrect ratio of gas and oil.


The above-listed issues are easily resolved. To solve them:

  • First, check whether there’s enough gas in the weed eater to power it. If there’s not enough gas top it off.
  • If there is gas in it and it is recently been added, there’s a chance it’s separated so you want to slightly shake your weed eater to remix it.
  • If there is gas in it but it’s old or leftover from last season, then you need to empty the fuel from the gas tank and mix one with the correct ratio of 2 cycle oil at a ratio of 40 parts unleaded gasoline to 1 part 2-cycle oil (check the gas cap or fuel tank to confirm your gas to oil ratio).


  • The gas you use should be 87% octane with no more than 10% alcohol.
  • Use oil designed for 2 cycle engines, not regular motor oil.
  • Invest in a good 2 stroke oil like the STIHL High Performance Engine Oil.
  • Do not mix the oil and gas in the gas tank, mix in a container beforehand to get a comprehensive blending.
  • Do not use gas that’s been in the tank for more than 90 days.
  • If you use the wrong ratio, it can cause your engine to seize, sputter, or overheat.
  • Always try to shake the fuel in the tank before every use of your weed eater.
  • If you’ve tried to start your trimmer too many times, let it rest for a few minutes before trying again.

2) Air Filter Issues

Air Filter Issues weed eater

The job of an air filter is to make sure air gets to the engine. This mixture of fuel and oxygen produces the initial spark and the power to get your engine running. The air filter also has a filter cover and a filter element that makes sure dirt in the air doesn’t get in the engine thereby causing damages. If after using your weed eater for a long time or maybe after taking it out of storage you can’t get your weed eater to stay running and it just starts and stops abruptly then the problem is most likely the air filter.


  • Find the black air filter box usually located at the back of the weed eater.
  • Unscrew the air filter box and pull it off.
  • There’s a thumbscrew that keeps the air filter box together. Unscrew that and expose the air filter which is made of re-useable cell foam.
  • Brush off any visible debris on the air filter.
  • Wash the filter with mild detergent and warm water, gasoline, or acetone.
  • If you use detergent, make sure it’s fully rinsed off and then squeeze off any excess liquid
  • Let the filter dry completely in a safe place
  • Put the filter back into the box and tighten the thumbscrew. Replace the box into the motor and then re-screw it back in.


  • If your filter foam is too dirty, then it’s better to buy a new one.
  • There’s a chance the filter might be paper instead of foam, these are not washable or reusable.
  • Change or clean your air filter at the beginning of every season.

3) Spark plug Problems

Spark plug Problems weed eater

Even with an air filter or gasoline-related issues the weed eater still responds but if there is no sign of your weed eater starting then the reason is most likely because of a faulty or dirty spark plug. The spark plug is what ignites your engine, sending that spark that causes it to start so when it’s faulty you probably won’t even get a small sputter out of your weed eater.


  • Remove the spark plug cover and take out the spark plug.
  • Clean the surrounding area of the spark plug.
  • Look at the spark plug to see if there are any cracks, if there are then it needs to be replaced with a new one which is usually pretty inexpensive.
  • If there aren’t any cracks and it’s simply dirty, clean with sandpaper, a wire brush, or spark plug cleaner.
  • Check to make sure the gap between the plug nodules is around .025 – .030. If it isn’t then adjust or replace it.
  • Refix the spark plug


  • Low-quality oil usually causes a faulty spark plug
  • Clean or change your spark plug after bringing it out of storage for the season or after your weed eater has been running for over 20 hours
  • If after the spark plug has been cleaned or replaced and it still doesn’t work, check the coil.

4) Ignition coil Problems

weed eater Ignition coil Problems

The ignition coil is what sends electrical current to the spark plug which in turn starts your engine. If the weed eater is still running rough or not starting after cleaning a replacing the spark plug then it’s time to check the ignition coil.

You can check the ignition coil with an ignition system tester, a cheap device that you can buy at the hardware store. Follow the following steps:

  • Insert the spark plug wire lead into the spark test.
  • Attach the alligator clip to the metal end at the tip of the spark plug.
  • Turn the ignition switch on
  • Pull the starter plug and check the window in the spark tester
  • If the spark is strong and blue then the ignition coil is fine. If there is little to no spark then the ignition coil needs to be replaced.


  • Except you really know your way around the engine, it’s better to take it to the shop for fixing.
  • Go ahead and watch this youtube video that shows you how to replace an ignition coil.

5) Carburetor Problems

weed eater Carburetor

The carburetor is an essential part of the engine and is the main reason your machine starts. That means if there’s a problem with it then you won’t be able to get your engine started. The problems that can occur with the carburetor include:

  • Clogged or dirty fuel filter. The carburetor has a fuel filter that might get clogged and full of debris over time. Some signs of this include sputtering of the engine, engine misfires, or strong odors.
  • Broken Priming Bulb. A priming bulb sends gas into the carburetor so it can create a fuel and air mixture that can go right into the cylinder to the engine running.
  • Worn out carburetor.


Clogged or Dirty Fuel filter. To clean out a fuel filter:

  • Remove the fuel filter and clean with the carburetor or solvent cleaner.
  • Wait for a few minutes to allow it to dissolve the debris.
  • Refix the fuel filter

Broken Priming Bulb and Worn-Out Carburetor:

The only option is to replace it with a new part. These are generally inexpensive and easy to get.


  • There are a lot of parts so make sure you know you’re capable of replacing the carburetor before disassembling it.
  • Consider cleaning other parts of the carburetor with a solvent cleaner for a more thorough cleaning.
  • If you’ll be cleaning or replacing the carburetor yourself, remember to disconnect the spark plug and protect yourself with gloves and goggles.

6) Spark Arrestor Screen Issues

Spark Arrestor Screen Issues

A spark arrestor is a screen that covers the exhaust outlet of a weed eater limiting the size of the particles in the exhaust gases coming out of the muffler which can cause a spark that leads to a fire. Signs include poor acceleration, lack of power, and a higher than normal “spit back” through the carburetor.


  • Take out the spark arrestor (you can refer to the manual to find where it is) and remove all screws blocking access to it.
  • Hold it with a small plier then use a butane torch to burn off all carbon on it.
  • Let it cool.
  • If there is still some residue on it, then you can clean it off with a non-metallic brush.
  • Refix the spark arrestor screen.


  • It’s better to simply buy a new one than to clean an old one.
  • If you do want to clean it, make sure you’re safe by wearing gloves and goggles.
  • Do not use a wire brush to clean as this can lead to faster plugging of dirt.
  • Clean it monthly or after long storage.

7) Flooded Engine Issues

Flooded Engine Issues

If you’ve repeatedly tried to turn on your weed eater or you’ve sat it on its side then you might have a flooded engine causing your weed eater not to start.


  • To unflood a weed eater:
  • Turn the on/off switch to “ON”.
  • Position the weed eater’s choke lever to run.
  • Pull the coil several times to remove the fuel. You will have to do this several times but continue until all the black smoke leaves the weed eater.
  • Let it rest for about 20 minutes before trying to turn it on again.

8) Electrical or Battery Problems

weed eater Electrical or Battery Problems

In the case that you have an electrical trimmer sometimes the fault is the most obvious one and that is the power source.


  • Make sure that the electrical outlet is drawing power.
  • Make sure all the cords are plugged in, on one side to the weed eater and on the other to the electrical outlet.
  • Check the extension, circuit breaker, and fuses to make sure they’re all functioning.
  • Make sure your weed trimmer is in the “ON” position.


  • Try not to overcharge the batteries as this reduces their lifespan.
  • Be careful not to drop the batteries because this damages them.


If you weed eater wont start, above are the most 8 common causes, A weed eater can last between 3-8 years with correct usage and maintenance. To make sure your weed eater lasts that long. You should:

  • Store the weed eater safely.
  • Use Ethanol-free fuel.
  • Invest in a better stroke oil.
  • Make sure you mix the gas and oil properly. If you can’t then go for one of the store-bought premixes.
  • Regularly maintain the weed eater by cleaning or changing the spark plug, air filter, fuel filter, and spark arrestor screen.

Do all these things and you’ll be able to use your machine for quite some time with no issues.

Leave a Comment