Stihl Trimmer Won’t Start—What To Do?

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If your Stihl trimmer won't start then, it can put a pause on your yard chores. So what could cause this problem, and how do you fix it? We have laid out the possible reasons your Stihl trimmer won't start in this article.

If your Stihl trimmer doesn't start, it could be due to the following:

  • Flooded Carbeurator
  • Clogged Air Filter
  • Clogged Fuel Filter
  • Clogged Spark Arrestor
  • Bad Spark Plug
  • Bad Gas/Oil Mixture
  • Engine Seized
  • Bad Recoil Starter
  • Faulty Recoil Pulley
  • Broken Rewind Spring
  • Damaged Flywheel
  • Bad Piston Rod Seal

As you can see, there are various reasons why your Stihl trimmer won't start. But, don't worry, because in the article we will talk about each issue and how to troubleshoot them. In addition, we will discuss other frequently asked questions about the Stihl trimmer, so read on!

A grass trimmer cutting unwanted grass in front of his lawn, Stihl Trimmer Won't Start—What To Do?

Stihl Trimmer Won't Start—What To Do?

A trimmer is a gardening tool used to cut grass and other plants around objects, such as trees, borders, and sidewalks. It is also used to edge lawns.

Trimmers typically have two sharpened metal blades powered by a gasoline engine. Some trimmers have a straight shaft, while others have an adjustable shaft. A bumped head is another feature on a trimmer that allows the user to drive more lines without stopping.

If you own a Stihl trimmer, but you are having issues starting it up, then there are a couple of things you can do. First, make sure that you are following the proper starting procedure. If you have done the proper starting procedure accorded to Stihl, you need to check the following parts.

Man using a red weed trimmer to remove overlapping weeds on the driveway

Flooded Carbeurator

One likely reason why your Stihl trimmer isn't starting is that it is flooded. If you are familiar with the operation of these engines, then you know that when they are flooded, they will either start after three or four pulls of the starter cord.

However, if your Stihl trimmer is not starting after multiple pulls, then it may be due to a flooded carburetor. Try turning the choke off and holding down the throttle while pulling the cord several times until it turns over.

Clogged Air Filter

This is another possible reason why your Stihl trimmer won't start. If the air filter is clogged, then it restricts airflow and prevents the ignition from taking place.

This also causes incomplete combustion. You need to replace the air filter or clean it to remove any debris to fix this issue.

Clogged Fuel Filter

A basic rule of thumb is that your Stihl trimmer should only be filled with fresh gasoline, not leftover gasoline from the previous season. If you use old gas, clogs will form in the fuel filter.

The good news is that these can be cleaned out. But if this doesn't work, you need to replace the fuel filter.

Clogged Spark Arrestor

Another possible reason your Stihl trimmer won't start is that it has a clogged spark arrestor. The spark arrestor prevents debris from getting sucked into the engine and causing damage, but this also prevents air and fuel mixture from taking place.

You need to replace the spark arrestor or clean it out by removing any debris to fix this issue.

Bad Spark Plug

If the spark plug is in bad condition, it may cause your Stihl trimmer not to start. The bad spark plug can happen when water is dropped into the cylinder, when the unit is left idle for a long time, or when too much oil accumulates on the electrode.

Bad Gas/Oil Mixture

If the gas-oil mixture is bad, then this also causes your Stihl trimmer not to start. As mentioned earlier, gasoline should be used up ultimately, and leftover gasoline from last season should never be used.

In addition, using oil that isn't from a quality brand can cause issues with your engine's ability to start.

Engine Seized

If you've tried all the possible solutions above, then the chances are that your Stihl trimmer engine is seized. You will need to take your Stihl into a service center and repair or replace the unit.

Bad Recoil Starter

If you have issues starting your Stihl trimmer, it may have a bad recoil starter. To test the recoil starter, you need to engage it by pulling the cord without pressing down on the throttle.

Remove any debris in the way of the generator rotor and housing; make sure both ends of the spring are hooked on. Also, make sure that the starter spring is not bent out of place too much, or else it will scrape the housing and cause damage.

Faulty Recoil Pulley

The recoil pulley is part of the starter mechanism and makes sure that the spring hooks onto the flywheel to provide optimum power. If this part is faulty, you won't be able to engage your Stihl trimmer's starter mechanism.

Broken Rewind Spring

A red weed trimmer trimming grass

The rewind spring is responsible for putting tension on the starter cord. This part can break and cause your Stihl trimmer not to start correctly.

If this part breaks, you will need to replace it immediately as it can lead to severe injury or damage if mishandled.

Damaged Flywheel

It may seem like a broken flywheel engine issue, but it is the recoil starter itself. If this part has any damage to it, then you won't be able to engage your Stihl trimmer's starter mechanism.

You need to replace the flywheel if there are any cracks, or else the piston cannot move freely and generate less power.

Bad Piston Rod Seal

If the piston rod seal is damaged, then this will cause your Stihl trimmer not to start. This part ensures that oil lubricates the engine, and a break or leak can make it difficult for you to engage your starter mechanism.

You need to replace the piston rod seal if there are any leaks, and you should also consider replacing the piston rod.

A Stihl trimmer not starting is a common problem for many users, but you can fix it by following the tips above. If all else fails, take your Stihl to the nearest service center to have them do any necessary repairs or replacements.

How do you check the spark on a Stihl trimmer?

The easiest way to check a spark on a Stihl trimmer is by using a spark plug tester. To do this, follow these steps:

  1. First, remove the boot to the spark plug housing.
  2. Next, attached one end of the spark plug tester to the inside of the boot.
  3. Now, attached the other end of the spark plug test to the spark plug.
  4. Lastly, pull the cord to see if a spark is coming from the spark plug.
  5. If it doesn't show a spark, the spark plug is worn and needs to be replaced.

So, how to Start a Flooded Stihl Weedeater?

To start a flooded Stihl weedeater, you will need to place the weedeater so the spark plug reservoir is facing down. Next, turn the choke on and pull the cord 15 or more times until the engine turns over. You may need to repeat these steps several times to unflood the engine.

Stihl Trimmer Won't Start When Hot

Grass debris scattered on the weed trimmer

A Stihl trimmer won't start when hot means an issue with the engine. To troubleshoot this problem, try the following steps:

First, check to ensure your choke or throttle is not in position.

Next, open up the spark plug housing and check to ensure you have a good spark coming from the spark plug. Also, make sure the spark plug is dry if you are using a new one, and attach it firmly to the engine.

Next, see if there is any oil coming from the bottom of your Stihl trimmer's air filter housing; if it looks like it has oil, then you probably need to replace your piston rod seal.

You may also have a blockage in one of the passages. Again, check the intake passage for any debris, and clean it out if necessary.

Make sure that the carburetor is clean and try replacing your fuel lines in a worst-case scenario; it will fix the issue in a best-case scenario.

Lastly, check your fuel/oil mixture. That might be the issue if you have old fuel in the tank.

Stihl Weedeater Won't Stay Running

Worker using a grass trimmer for the backyard lawn

If your Stihl weedeater will start but won't stay running, it could be several different problems. First, make sure there is gasoline in the fuel tank; if not, fill it up with fresh gas.

Next, check your carburetor for any obstructions or cracks, and clean it out if necessary. Also, check that the air filter, oil filter, or spark arrestor aren't clogged. If any of these are clogged, it will cause your Stihl weedeater not to stay on.

Final Thoughts

A grass trimmer cutting unwanted grass in front of his lawn

If you follow these tips, a Stihl trimmer not starting isn't always an easy problem to fix. First, try troubleshooting the parts mentioned in this article. If all else fails, take your Stihl to the nearest service center or with a dealer for any necessary repairs.

For more articles like this one, then check out our website:

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