How To Know: Replacing The Fuel Bulb In A Weed Wacker

A weed wacker, also known as a string trimmer, is a gardening tool that draws fuel from its tank to the carburetor via the primer. The primer bulb is a small plastic bulb with an attached line that feeds the trimmer fuel. Over time, the bulb can become clogged or tangled, and cracks or holes can appear in the plastic. If the bulb is damaged, it is important to replace it. Primer bulbs are cheap and easy to replace. To do so, you will need to drain the remaining gas from the trimmer tank into a fuel container, pull out the fuel line and fuel filter from the engine using a pair of needle-nose pliers, and then replace them with new ones, ensuring that they fit your brand.

Clogged Primer Bulb and Line

A clogged primer bulb and line is one of the most common reasons why a string trimmer won't prime. The primer is a small plastic bulb with an attached line that feeds the trimmer with fuel. Pressing the primer a few times before starting the trimmer delivers the fuel. If the primer is not pressed enough times, it may be the reason for the engine not running.

To fix this, first, fully press and then release the primer for another 10 times to see if that solves the problem. If the issue persists, the bulb may be damaged. Check the primer bulb for any damage, such as cracks or holes, as these can appear in the plastic over time. If the bulb is intact, examine the visible line to ensure it is not tangled or pulled. The primer is used for "cold" starts, so if you're running out of fuel or if the primer is being used after warming up, the carburetor or fuel line may be damaged and need to be serviced.

If the bulb is damaged, it is recommended to replace it. Primer bulbs that are cracked can be easily and cheaply replaced. Replacement primer bulbs can be purchased online or at a local hardware store. Ensure that the replacement bulb fits your brand of the string trimmer.

Faulty Carburetor

A faulty carburetor could be the reason why your weed wacker won't start. The carburetor is located near the choke and primer bulb, and it combines air and gas into a combustible mixture that ignites in the cylinder to power the engine. If your weed wacker's gas tank is full but the engine won't start, the carburetor is likely the problem.

Identifying a Faulty Carburetor

Before you begin, disconnect the spark plug wire and drain the fuel tank into an approved storage container.

• Remove the air filter and add a small amount of fuel (about a teaspoon) to the carburetor.
• If the engine starts and then quickly dies when you pull the starter cord, the carburetor is likely faulty.
• Check the fuel lines connected to the carburetor. If they are blocked, gently pull them off using needle-nose pliers, turn the trimmer upside down, and check if there are drops of fuel.
• If there are no fuel drops, the fuel is not reaching the carburetor, and the fuel lines will need to be replaced.
• If the fuel lines are intact, the carburetor may be clogged and need to be cleaned or replaced.

Cleaning the Carburetor

• Remove the air filter and spray carburetor cleaner into the intake.
• Let the cleaner sit for several minutes to loosen and dissolve any varnish or debris.
• Replace the filter and attempt to start the trimmer.

Disassembling and Rebuilding the Carburetor

If cleaning the carburetor does not solve the problem, you may need to disassemble and rebuild it. This process can be challenging, as it involves delicate components, so proceed with caution:

• Take pictures with your phone throughout the process to aid in reassembly.
• Clean all the openings and passages with carburetor cleaner.
• If you are uncomfortable with disassembling the carburetor, take it to a servicing dealer.

Replacing the Carburetor

If cleaning or rebuilding the carburetor does not work, you may need to replace it. Install a manufacturer-approved carburetor that fits your specific weed wacker model.

• Disconnect the fuel lines and the throttle control cable from the carburetor.
• Remove the carburetor mounting screws and pull off the air filter housing.
• Lift the carburetor off the engine.
• Insert the throttle cable on the new carburetor the same way it was installed on the original one.
• Position the gasket on the engine mount nipples and hold the carburetor in place.
• Install the filter housing and secure it with the mounting screws. Tighten the screws with a torque wrench to 25 in./lbs. of torque, or reasonably tightly if you don't have a torque wrench.
• Reconnect the fuel lines, referring to your pictures or diagrams for correct placement.
• Reinstall the air filter and spark plug, and refill the gas tank with the fuel mix.
• Test the weed wacker to ensure it is now functioning properly.

By following these steps, you can identify and address a faulty carburetor in your weed wacker, ensuring it starts and runs smoothly.

Fuel Return Line

The fuel return line is an important component of a weed wacker, ensuring the efficient flow of fuel from the tank to the carburetor. Here's a comprehensive guide to understanding the fuel return line and when to replace it:

Understanding the Fuel Return Line

The fuel return line is a vital part of the weed wacker's fuel system. It is one of two lines that connect the fuel tank to the primer bulb and the carburetor. The fuel return line is typically thicker than the fuel feed line, which is the thin line that supplies fuel from the tank to the carburetor. The return line serves as a breather, allowing air to enter the tank and facilitating the flow of fuel.

When to Replace the Fuel Return Line

Over time, the fuel return line can become damaged or worn, requiring replacement. Here are some signs that indicate it's time to replace the fuel return line:

• Visible Damage: If you notice any cracks, cuts, or holes in the fuel return line, it needs to be replaced. Such damage can disrupt the proper flow of fuel and ventilation in the system.
• Disconnection from the Tank: If the fuel return line is no longer connected to the fuel tank or primer bulb, as in the case of a sheared-off connection, replacement is necessary. This issue can prevent fuel from returning to the tank properly.
• Clogging or Tangling: In some cases, the fuel return line may become clogged or tangled, impeding the normal flow of fuel and ventilation. If cleaning or untangling the line does not resolve the issue, replacement may be the best option.
• Age and Performance Issues: If your weed wacker is experiencing performance problems, such as frequent stalling or difficulty starting, and the fuel return line is older, it may be wise to replace it. This is especially true if the line shows signs of deterioration or brittleness.

Replacing the Fuel Return Line

When replacing the fuel return line, it is essential to purchase a compatible replacement kit that includes both the fuel filter and the correct type of fuel line for your specific weed wacker model. Here are the general steps to replace the fuel return line:

• Disconnect the Old Line: Start by carefully detaching the old fuel return line from the primer bulb and fuel tank. You may need to cut or remove any remaining portions still connected.
• Prepare the New Line: Cut the new fuel line to the appropriate length, ensuring that it fits securely between the fuel tank and the primer bulb.
• Connect the New Line: Attach one end of the new fuel return line to the primer bulb, following the specific connection method for your weed wacker model. Then, insert the other end of the line into the fuel tank. Ensure that the line has sufficient slack inside the tank to move freely and reach the fuel.
• Secure the Connection: Some weed wacker models may require an additional locking washer or similar mechanism to secure the fuel return line connection at the fuel tank. Refer to your weed wacker's instructions or seek advice from a small engine repair specialist.

By following these guidelines and staying vigilant about the condition of your weed wacker's fuel return line, you can ensure optimal performance and extend the life of your equipment.

Fuel Filter

The fuel filter in a weed wacker is an important component that ensures the smooth flow of fuel from the tank to the carburetor. It is connected to the primer bulb and plays a crucial role in the fuel delivery system. Over time, the fuel filter can become clogged or damaged, leading to poor engine performance or even failure. Here are some signs that indicate when it is time to replace the fuel filter in your weed wacker:

• Clogged Fuel Filter: The primary function of the fuel filter is to prevent impurities and debris from entering the carburetor. However, the filter itself can become clogged over time, restricting the flow of fuel. If you notice that your weed wacker is not receiving enough fuel or is struggling to start, it may be due to a clogged fuel filter.
• Damage or Wear: Visual inspection of the fuel filter can reveal signs of damage or wear. If you notice cracks, holes, or any other form of degradation on the filter, it is essential to replace it. A damaged fuel filter will not effectively filter the fuel, allowing contaminants to enter the carburetor and potentially causing engine damage.
• Engine Performance Issues: If your weed wacker is experiencing performance issues, such as rough running, loss of power, or frequent stalling, a faulty fuel filter could be the culprit. A restricted or clogged fuel filter can disrupt the optimal fuel-air mixture, leading to poor engine performance.
• Fuel Leakage: If you notice fuel leaking from the weed wacker, it could be due to a faulty or damaged fuel filter. Leaks can occur if the filter is not securely connected or if it has degraded over time. In such cases, replacing the fuel filter and ensuring proper connections can remedy the issue.
• Difficulty Starting the Engine: A weed wacker that is challenging to start, especially after extended periods of inactivity, may indicate a problem with the fuel delivery system. A clogged or faulty fuel filter can impede the flow of fuel, making it difficult for the engine to start.

Replacing the fuel filter in your weed wacker is a relatively straightforward process. Here are the general steps to replace the fuel filter:

• Purchase a compatible replacement fuel filter for your specific weed wacker model. Ensure that the new filter is designed to fit your machine and is of good quality.
• Drain the remaining fuel from the tank to avoid spills or mess during the replacement process. This can be done by safely transferring the fuel to an appropriate container.
• Disconnect the fuel lines from the carburetor and primer bulb, taking note of the routing and connections. You may need to use needle-nose pliers to carefully detach the lines.
• Remove the old fuel filter from the fuel tank. This may require some manipulation with tools to carefully extract the filter without damaging any surrounding components.
• Install the new fuel filter by following the reverse steps of removal. Ensure that the filter is securely connected to the fuel lines and positioned correctly inside the tank.
• Reattach the fuel lines to the carburetor and primer bulb, mirroring the original setup. Ensure that all connections are secure and that there is no leakage.
• Refill the fuel tank with fresh fuel and check for any signs of leakage around the fuel filter and lines. Start the weed wacker and observe if it runs smoothly, indicating a successful fuel filter replacement.

It is important to consult your weed wacker's user manual or seek guidance from a qualified technician if you are unsure about the replacement process. Regular maintenance and timely replacement of the fuel filter will help ensure the optimal performance and longevity of your weed wacker.

Fuel Tank

The fuel tank in a weed wacker is connected to the primer bulb by a fuel line. The primer bulb pumps air into the tank, which then pushes the gas into the carburetor. The fuel tank should not be more than 90% full, and the contents should not be more than 90 days old. The fuel tank has a thick line and a thin line running to it from the carburetor. The thin line is the fuel feed, and the thick line is the fuel return/breather.

The fuel tank should be examined for damage, and the gas vent should be open. If the fuel tank is damaged, it may need to be replaced. If the connection to the fuel tank has been sheared off, as in the case of a Ryobi 750r weed wacker, it is possible to buy a filter/line kit that includes a fuel filter and a fuel line. The fuel tank can also be replaced.

When replacing the thin line, it is important to connect it to the filter inside the tank. Pull out about 1" of fuel line from the fuel cap opening and attach the filter. Replace the line back into the tank, allowing the fuel filter/line to flop around inside the tank. The same line then goes from the tank to the bottom connector on the carburetor.

It can be challenging to insert the rubber hoses into the tank, and a long pair of needle-nose pliers may be needed to pull the lines through. One trick is to cut the tips of the hoses at a sharp angle to make a V-shape, drill a small hole in the V-shape, insert wire through the hole, and then use the wire to pull the hose through.

If the fuel lines are intact but fuel is not reaching the carburetor, the carburetor may need to be cleaned of buildup or replaced.

Frequently asked questions