Replacing The Fuel Tank Pressure Sensor In A W204: Step-By-Step Guide

If you're experiencing poor engine performance or hard starting problems with your Mercedes-Benz W204, you may need to replace the fuel pressure sensor. This is a fairly common issue with this model, and it can cause significant engine problems if left unattended. The fuel pressure sensor is located in the lid of the fuel filter, under the left rear seat. It's important to note that there are several different types of filters and pumps for the W204 family, so it's recommended to have your VIN handy when ordering parts.

Remove the rear bench seat to access the sensor

To remove the rear bench seat of a Mercedes-Benz W204, you will need the following tools: a trim removal tool, an E12 socket, and a T45 Torx driver. This process will take around two hours.

First, remove the rear seat cushion. There are two friction clips on each side of the bench. Grab the bench at the front by the clips and pull straight up. With the bench lifted, you will see a metal hoop attached to the bench that sits in a friction clip in the chassis.

Next, slide the bench back and lift it up and then pull it forward and out. There is a metal hook on the bottom of the bench that you cannot see, but it is approximately where the red arrow is on each side in Figure 9 of the Pelican Parts DIY Maintenance Article.

Now, you will need to remove the rear seat back section. Use a T25 Torx and remove the Torx screw that holds the side of the seat back (one on each side), and then remove the two 16mm nuts (one shown).

Open the trunk and climb in. Use a flathead screwdriver to release the two latches. Insert the screwdriver into the two holes under the rear chassis cross member, and slide the screwdriver to the left. This will release the upper latches that hold the seat backs in place. You can now remove the seat back from the vehicle.

Please note that installation is the reverse of removal.

Disconnect the electrical connection from the sensor

To disconnect the electrical connection from the sensor, you will first need to open the fuel filler door and remove the gas cap to relieve the pressure in the system. This is an important safety step as fuel and fuel vapors are highly combustible.

Next, you will need to remove the rear bench seat to access the sensor. Please refer to our article on seat removal for detailed instructions on this step. Once the seat and padding have been removed, you will see the access cover for the filter and sensor under the rear left seat.

Use an 8mm socket to remove the four bolts securing the access cover in place. Lift the cover off and carefully peel back the sealant around the wiring pass-through. This will expose the fuel pressure sensor, which is located in the lid of the fuel filter.

Now, you can proceed to disconnect the electrical connection from the sensor. This step requires careful handling as you will be working in close proximity to fuel. Ensure that you are wearing proper clothing, gloves, and safety glasses. It is also recommended to work in a well-ventilated area, preferably outdoors.

After disconnecting the electrical connection, you can continue with the next steps of the replacement procedure. Remember to work with caution and always prioritize your safety when working with automotive systems, especially those involving fuel.

Remove the sensor by pulling back the metal clip

To remove the sensor, you will need to apply hand pressure to the metal clip to pull it back out from the lid. You should not need to use excessive force to do this. The metal clip is holding the sensor in place in the lid, so once you have pulled it back, you can carefully lift the sensor straight up and out from the lid.

Be sure to clean around the sensor and the lid before removing the sensor. There will be a small O-ring that seals the sensor to the lid, so be careful not to damage this when removing the sensor. When you reinstall the sensor, place a small amount of clean gas on the O-ring.

Clean around the sensor and lid

To clean around the sensor and lid, you will need to carefully remove any dirt or debris that has accumulated in the area. This is important to ensure that no contaminants enter the fuel system when the sensor is removed.

Start by using a soft, clean cloth to wipe down the area. You can lightly dampen the cloth with a small amount of water or a mild cleaning solution if needed, but be careful not to let any liquid come into contact with the electrical components of the sensor.

If there is any built-up grease or grime, you may need to use a mild solvent to help break it down. Apply the solvent to a clean cloth and gently rub the affected areas until the grease is removed. Be sure to choose a solvent that is safe for use on automotive components and avoid getting it on any plastic or rubber parts, as it may cause damage.

Once you have finished cleaning, use a dry cloth to wipe away any remaining residue or moisture. It is important to ensure that the area is completely dry before proceeding with the sensor replacement.

Additionally, it is recommended to wear proper clothing, gloves, and safety glasses when working with fuel system components, as well as working in a well-ventilated area to avoid inhaling fumes.

Pull the sensor straight up and out from the lid

Now that you have cleaned around the sensor and lid, you are ready to remove the sensor. Pull the sensor straight up and out from the lid. You will notice a small O-ring that seals the sensor to the lid. When you are reinstalling the sensor, place a small amount of clean gas on this O-ring. The installation is the reverse of the removal process.

It is important to note that when working with gas, you should wear proper clothing, gloves, and safety glasses. It is also recommended to work in a well-ventilated area, preferably outdoors. Do not use incandescent work lights or power tools, and refrain from smoking as fuel and fuel vapors are highly combustible.

Additionally, before beginning the replacement process, ensure that you have the correct parts for your specific vehicle. The fuel pressure sensor is VIN-specific, and there are several different types of filters and pumps for the W204 family. Have your VIN handy when ordering parts.

Frequently asked questions