How to start a flooded weedeater engine + trimmer maintenance

Monday, January 30, 2023
Gasoline-based weed eaters can flood when there is an overabundance of fuel in the engine, which prevents it from starting. This can occur when the choke is engaged while trying to start a warm engine, causing more gasoline to enter the combustion chamber than what is needed. The excess fuel can mix with air and cause a rich fuel-to-air ratio, which can flood the engine of your grass trimmer and prevent it from starting.

Flooding in a 'weed whip' can also occur when the primer bulb is pumped excessively, causing too much gasoline to enter the fuel line. This can lead to the same rich fuel-to-air ratio in the combustion chamber, and the engine will not start. 

Excess gasoline can also seep into the spark plug and prevent it from firing, further exacerbating the flooding issue.

To clear the flood, it is necessary to wait until the excess fuel has evaporated, which can take a few minutes. After that, the 'line trimmer' can be restarted and should run normally. If the engine still does not start, it is recommended to check the spark plug for any gasoline residue and clean it if necessary.

Husqvarna 324L 4-Cycle 18" Cutting Path Gas String Trimmer

Step-by-Step Guide to Starting a Flooded Weed Eater:

  1. Wait patiently: Wait a few minutes before attempting to start it. This will allow the excess fuel a chance to evaporate and reduce the risk of further flooding (because you'll simply just add more excessive fuel!).
  2. Remove the spark plug: Take out the spark plug and inspect it for any gasoline residue. If there is any gasoline on the spark plug, clean it with a cloth.
  3. Clear the Fuel Line: Remove the fuel line from the carburettor and drain any excess fuel into a container. This will help to clear the fuel system and prevent further flooding. This one is more of a last desperate measure, you shouldn't generally need to do this.
  4. Prime the engine: Now, you're at the business end of the 'unflooding'. Pump the primer bulb a few times to bring fuel into the carburettor and fuel line. This will help to prime the engine and get it ready to start.
  5. Disengage the Choke: Make sure that the choke is in the off position before attempting to start the engine. Engaging the choke while starting a warm engine can cause it to flood!
  6. Pull the Starter Rope: Pull the starter rope slowly and steadily until the engine starts. If the engine does not start on the first try, wait a few seconds and then try again.
  7. Warm Up the Engine: Once the engine has started, let it run for a few minutes to warm up. This will help to clear any remaining fuel from the combustion chamber and prevent future flooding.

Why do some weedwhacker seem to continually self flood?

Sometimes it's not your fault! 

Garden lawn and edge trimmers can flood repeatedly due to several reasons, including the following:

Carburetor Issues: A clogged or dirty carburetor can cause the engine to flood. A 2-cycle carburettor mixes fuel and air in a specific ratio to provide the engine with the correct fuel mixture. If the carburetor is clogged or dirty, the fuel mixture can become too rich, causing the engine to flood.

Stiff Metering Diaphragm: A stiff metering diaphragm can also cause the engine to flood. The metering diaphragm regulates the amount of fuel that enters the carburetor. If it is stiff, it may not be able to regulate the fuel mixture properly, causing the engine to flood.

Needle Valve: The needle valve is responsible for controlling the flow of fuel into the carburetor. If the needle valve is not adjusted correctly, it can cause the engine to flood.

In order to prevent repeated flooding, it is important to regularly maintain the carburettor and check the metering diaphragm and needle valve for proper function. If the engine continues to flood, it may be necessary to clean or rebuild the carburetor, replace the metering diaphragm, or adjust the needle valve.

Here's a great Youtube lesson on how to remedy such issues.

how to start a flooded weed trimmer

Here are the steps for adjusting the needle valve in a grass trimmer:

  1. Locate the Carburetor: The needle valve is located under the carburettor, so first locate the carburettor on your grass trimmer and remove it and the diaphragm.
  2. Locate the Needle Valve: The needle valve is a small, cylindrical component with a screw that protrudes from the top.
  3. Use a small screwdriver to turn the needle valve screw clockwise to increase the fuel flow or counterclockwise to decrease the fuel flow. In the case of over flooding, you'll want to decrease fuel flow...
  4. Now put it all back together...
  5. Test the Engine: After adjusting the needle valve, start the engine and run it at full throttle for a time. Keenly observe the engine's performance and listen and look for any signs of flooding. You'll know if the flooding problem recurs.
  6. If necessary, repeat the adjustment process until the engine runs smoothly at full throttle.

Here are 7 general tips for maintaining a weed eater:

  • Use Fresh Fuel: Always use fresh fuel and mix it with the recommended oil in the correct ratio to ensure the engine runs smoothly.
  • Clean Air Filter: Regularly check and clean the air filter to prevent clogging and ensure the engine receives enough air.
  • Check Spark Plug: Regularly check the spark plug and replace it if necessary to ensure the engine starts easily and runs smoothly.
  • Lubricate Moving Parts: Regularly lubricate the moving parts to reduce wear and tear and extend the life of the weed eater. We personally use CRC lubricant.
  • Check Fuel Line: Regularly check the fuel line for cracks or leaks and replace if necessary to prevent fuel from spilling. Most garden centres and tool shops carry replacement lines. 
  • Check Fuel Filter: Regularly check the fuel filter for clogging and replace if necessary to ensure the engine receives enough fuel.
  • Store Properly: Store the weed eater properly to prevent damage and extend its life. Clean it after use and store it in a dry place.
  • Check that the spark plug is correctly gapped. You will need to make an adjustment if it is not as your trimmer's engine will perform less efficiently than it could. 
That advice was more related to the engine side of things. 

Your 'brush cutter's trim line needs to be looked after too!

  • Remove the Spool: Locate the spool on the trimmer head and remove it by pressing the release button or turning the spool retainer.
  • Measure the Line: Measure the length of line needed and cut it to size. The length of line needed will depend on the size of the trimmer and the manufacturer's specifications.
  • Load the Line: Load the line onto the spool by winding it around the spool in the direction indicated by the arrow. Leave a small amount of line sticking out from both ends of the spool.
  • Replace the Spool: Replace the spool on the trimmer head and secure it by pressing the release button or turning the spool retainer.
  • Adjust the Tension: Adjust the tension on the trimmer line by turning the adjustment screw on the trimmer head. The line should be tight enough to prevent it from slipping, but not so tight that it is difficult to turn the trimmer.
To maintain the trimmer line, it is important to keep it clean and free of debris. After each use, clean the trimmer head and line to remove any grass clippings or other debris that may have accumulated.

What is the correct fuel and oil mix for a gasoline weed trimmer?

fuel mix bottle
The correct fuel and oil mix for a gasoline weed trimmer depends on the manufacturer's specifications. Generally, a 2-cycle engine requires a mixture of gasoline and oil to lubricate the engine and prevent damage. The ratio of fuel to oil can vary, but a common ratio is 50:1, which means 50 parts gasoline to 1 part oil.

It is important to use a high-quality, unleaded gasoline and a 2-cycle oil specifically designed for air-cooled engines. The oil should be added to the gasoline in a clean container and mixed thoroughly before adding it to the fuel tank.

It is important to follow the manufacturer's instructions for the correct fuel and oil mix. Using the wrong fuel or oil, or not mixing the fuel and oil correctly, can cause damage to the engine.

Here are some general instructions on how to safely use a line trimmer

Always wear safety glasses or goggles, hearing protection, sturdy shoes or boots, and long pants and sleeves to protect your eyes, ears, feet, and skin from debris.

Follow the manufacturer's instructions for starting the trimmer. Start the engine on level ground, away from flammable objects, and with the trimmer head pointed away from you.

 Hold the trimmer with both hands, keeping your arms and legs away from the cutting area. Cut in a sweeping motion, moving the trimmer back and forth to cover the entire area. Avoid cutting too high or too low, which can damage the trimmer or the vegetation.

Be mindful of obstacles such as rocks, roots, or fence posts that can damage the trimmer or cause injury. Stop the trimmer if you encounter an obstacle and check for damage.

Always turn off the engine before setting down the trimmer or making any adjustments. When you need to stop the trimmer, release the throttle and wait for the cutting head to stop rotating before setting it down.

If someone approaches your working space (even your dog!), stop cutting until they have passed away.

Do not remove the 'debris shield' built into your trimmer.

Always cut away from yourself. Don't play any games or cut at odd angles or safe trim whilst at the top of a ladder to trim a tree...

By following these safety instructions, you can reduce the risk of injury and ensure that you use your line trimmer in a safe and effective manner.
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