Replacing The Fuel Filter On A Stihl Fs90r: Step-By-Step Guide

The Stihl FS90R is a 4-Mix string trimmer that uses a fuel filter to remove contaminants from the fuel before it enters the carburetor. The fuel filter is located inside the fuel tank at the end of the incoming fuel line. When the trimmer becomes difficult to start or stalls frequently even with a full tank of fuel, it may be time to change the fuel filter. This guide will cover the steps to change the fuel filter on a Stihl FS90R trimmer.

Identify the fuel filter

To identify the fuel filter on a Stihl FS90R, you will first need to locate the spark plug and plug wire on the trimmer engine housing. The spark plug is situated near the top rear of the housing, and the spark plug wire boot is the part of the wire that connects to the top of the plug. Once you've located these, you can grasp the sparkplug wire boot with your fingers and pull it off the sparkplug.

Next, you will need to remove the fuel cap by twisting it counterclockwise. Siphon the fuel from the tank into a container using a hand siphon and dispose of the fuel appropriately. Now, look inside the fuel tank for the fuel line lying at the bottom of the tank. The fuel filter, or pickup, will be found at the end of this fuel line.

The fuel filter is a small, disk-shaped component, usually black in colour, attached to the end of the fuel line inside the fuel tank. It can be removed using needle-nose pliers or long-nose tweezers. To replace the fuel filter, simply pull the old one off the end of the fuel line and push the new one on until it is firmly in place.

Empty the fuel tank

Emptying the fuel tank of your Stihl FS90R is a crucial step in changing the fuel filter. Here is a detailed guide on how to do it safely and effectively:

Firstly, locate the spark plug and spark plug wire on your trimmer engine. The spark plug is situated near the top rear of the engine housing, and the spark plug wire boot connects to the top of the plug. Using your fingers, carefully grasp the spark plug wire boot and gently pull it away from the spark plug. Bend the wire to the side to ensure that the boot doesn't accidentally touch the spark plug while you work.

Next, you will need to remove the fuel from the tank. Twist the fuel cap counterclockwise and lift it off the tank. Now, using a hand siphon, carefully siphon the fuel from the tank into an appropriate container. It is essential to dispose of the fuel responsibly and according to local regulations.

With the fuel safely removed, you can now focus on the fuel line and filter. Look inside the fuel tank, and you will see the fuel line lying at the bottom of the tank. The fuel filter, also known as the pickup, is attached to the end of this fuel line.

To remove the fuel line and filter, you can use a pair of needle-nose pliers. If needed, tilt the trimmer to move the fuel line closer to the tank opening, making it easier to grasp with the pliers. Gently pull the fuel line and filter out of the tank, being careful not to spill any remaining fuel.

Now that the fuel tank is empty, you can proceed to the next steps of changing the fuel filter on your Stihl FS90R. Remember always to dispose of old fuel and filters properly and to take necessary safety precautions when working with fuel.

Remove the spark plug wire boot

To remove the spark plug wire boot, start by locating the spark plug and plug wire on your Stihl FS90R trimmer. The spark plug is situated near the top rear of the trimmer engine housing. The spark plug wire boot is the part of the wire that connects to the top of the plug.

Using your fingers, grasp the spark plug wire boot and gently pull it straight off the spark plug. Be careful not to pull on the wire itself, as this could cause damage. Once the boot is removed, bend the wire to the side and away from the spark plug to prevent accidental contact.

It is important to keep the spark plug and wire away from the fuel tank and any fuel lines during this process to avoid any accidental sparks that could cause an explosion or fire. Ensure you are working in a well-ventilated area and that the engine is turned off before proceeding.

Now that the spark plug wire boot is removed, you can continue with the next steps of changing the fuel filter. Remember to keep the wire away from the spark plug until you are ready to reassemble the parts.

Remove the fuel cap and siphon the fuel

To remove the fuel cap and siphon the fuel from your Stihl FS90R, follow these steps:

First, locate the spark plug and spark plug wire on your trimmer. The spark plug is situated near the top rear of the trimmer engine housing. The spark plug wire boot is the part of the wire that connects to the top of the plug. Grasp the spark plug wire boot with your fingers and gently pull it away from the spark plug. Set it aside carefully, bending the wire to the side to avoid any accidental contact with the spark plug.

Now, you can twist the fuel cap counterclockwise and remove it from the fuel tank. Before siphoning the fuel, it is important to have a suitable container ready. Use a hand siphon to carefully draw the fuel from the tank into the container. Ensure that you dispose of the fuel in a proper and safe manner.

At this stage, you have successfully removed the fuel cap and siphoned the fuel. You can now proceed to locate the fuel line and gas filter inside the fuel tank.

Pull out the fuel line

To pull out the fuel line, you will need to first remove the carburetor. Spray the connector with WD-40 and carefully pry up the tab of the connector until it pops out. This will expose the fuel line.

Now, you can use a small hook or needle-nose pliers to pull out the fuel line. If you are struggling to reach the fuel line, tilt the trimmer to move the fuel line closer to the tank opening. Once you have a good grip on the fuel line with your pliers, carefully pull it out.

It is important to note that the fuel line is not one continuous piece. It is separated by a connector on the fuel tank. Be gentle when pulling out the fuel line to avoid any damage.

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