Replacing Ryobi String Trimmer Fuel Primer Bulb: Step-By-Step Guide

If you're looking to replace the fuel primer bulb on your Ryobi string trimmer, you've come to the right place. This is a relatively easy fix that you can do yourself in about 15 minutes with the right tools and parts. The primer bulb pumps fresh fuel into the trimmer's carburetor, making the engine easier to start. Due to constant exposure to fuel, the primer bulb will eventually deteriorate and need to be replaced. You can find a step-by-step guide on how to replace the primer and hose assembly on a Ryobi trimmer, as well as tune-up kits and replacement bulbs available for purchase.

Remove the rear cover

To remove the rear cover of your Ryobi string trimmer, you will need a screwdriver. The first step is to remove the four screws that are holding the rear cover in place. Once you have removed these screws, you can then take off the rear cover from the engine. It is important to note that before you begin any work on your trimmer, you should drain any excess fuel from the fuel tank. This will ensure that you avoid any accidental spillages while you are working.

Once the rear cover is removed, you will be able to access the carburetor. The next steps will involve detaching the carburetor and removing the fuel lines from the primer assembly. However, as the focus is on removing the rear cover, the next steps are beyond the scope of this response.

Detach the carburetor

To detach the carburetor, you must first drain any excess fuel from the fuel tank. Once this is done, remove the two screws from the carburetor assembly and carefully lift this away from the engine. Next, you will need to remove the choke plate and choke assembly from the carburetor. The throttle cable is then disconnected from the carburetor using a lift-and-twist motion.

Remove fuel lines from the primer assembly

To remove the fuel lines from the primer assembly, you will first need to drain any excess fuel from the fuel tank. This is an important safety step and will also make the process less messy.

Once the fuel tank is empty, locate the two fuel lines connected to the back of the primer assembly. These lines will be attached to the different length inlets/outlets on the primer assembly. The fuel return line (between the primer and the fuel tank) will be attached to the longer stem, and the line between the carburetor and the primer will be attached to the shorter stem.

You can now disconnect the two fuel lines from the primer assembly. They should pull away from the assembly relatively easily by hand. If you are struggling to remove them by hand, you can use long-nosed pliers to gently pull them away.

Before removing the lines, it is helpful to take a photo or draw a diagram of the existing configuration. This will make it easier to remember how to reconnect the lines when installing the new primer assembly.

Remove the primer assembly

To remove the primer assembly, you will need to first drain any excess fuel from the fuel tank. Next, disconnect the two fuel lines from the back of the primer assembly. These lines should be pulled away by hand, but if needed, long-nose pliers can be used to remove them.

The primer assembly is held in place by two plastic locking tabs. Compress these with long-nose pliers to release the primer assembly from its base. Finally, remove the assembly by sliding it toward the back of the trimmer and away from the trimmer head.

It is recommended to take a photo or draw a diagram of the existing configuration before removing the fuel lines, as the connection inlets/outlets on the back of the primer assembly are different lengths.

Install the new primer assembly

To install the new primer assembly, you must first align the tab on the new primer assembly (found beneath the short inlet) with the slot on the mounting base. Then, press or snap the new primer assembly into the mounting base.

The primer kit comes with a new piece of fuel line. To remove the old fuel line, pull the line (which was disconnected earlier) through the carburetor mounting plate (toward the carburetor). It should pull away from the carburetor relatively easily, but long-nosed pliers can be used if necessary.

Now, install the new fuel line onto the carburetor. Pass the new fuel line through the hole in the carburetor mounting assembly.

Finally, connect the new fuel line to the primer assembly. The line from the carburetor attaches to the short inlet on the primer, and the fuel return line attaches to the long inlet.

Frequently asked questions