Replacing The Fuel Pump In A W211 E55: Step-By-Step Guide

Replacing a fuel pump on a W211 E55 can be a complex task and should only be attempted by those with the necessary knowledge and experience. The fuel pump is located inside the fuel tank on the passenger side of the vehicle. Before beginning any work, it is important to disconnect the battery and to work in a well-ventilated area due to the risk of gas fumes and leaks. Once the necessary safety precautions have been taken, the next steps are to access the fuel pump by removing the rear seat and protective liner, followed by unscrewing the bolts holding the fuel pump assembly cover in place. The fuel pump can then be removed by disconnecting the wiring harness, fuel line, and holding brackets. When installing the new fuel pump, the process is reversed, ensuring that all components are securely connected and bolted down. It is also important to note that there may be variations in the specific steps and tools required depending on the model year of the vehicle.

Disconnect the battery

Disconnecting the battery is the first step in replacing the fuel pump on your W211 E55. This is a critical safety precaution as you will be exposed to gas fumes and potential fuel leaks during the fuel pump replacement process.

Step 1: Before disconnecting the battery, ensure you have the appropriate tools. For the W211 E55, you will need a 10mm socket, a 13mm socket with a ratchet and extensions, and a 10mm wrench.

Step 2: Locate the battery. The battery is positioned on the right side of the trunk.

Step 3: Start by disconnecting the negative (black) terminal first. Loosen the 10mm fastener and pull the battery cable off the negative battery terminal. It is important to always disconnect the negative terminal before the positive to prevent short circuits.

Step 4: Cover the negative battery terminal with insulating material to prevent accidental contact. This is an essential safety precaution.

Step 5: Next, move to the positive (red) terminal. Loosen the 10mm fastener and pull the battery cable off the positive battery terminal.

Step 6: At this point, the battery is disconnected. However, there is an additional step to ensure the battery is completely isolated.

Step 7: Pull the vent tube off its port on the back of the battery. This will ensure the battery is fully disconnected from the vehicle's electrical system.

By following these steps, you will have safely disconnected the battery in your W211 E55, allowing you to proceed with the fuel pump replacement process. Remember to work in a well-ventilated area and take the necessary precautions to avoid any potential hazards associated with handling fuel and electrical systems.

Prep access to the fuel pump

To prep access to the fuel pump, you must first make your way into the rear of the car. Start by lifting up the bottom of the passenger seat. The seat will snap at the front edge and will pop out with force. Once the seat is out, remove the protective liner and metal lid on top of the fuel pump assembly.

This will expose six bolts; use your ratchet and socket to remove those. Be sure to have the correct tools for the job. For the W211, you will need an 8mm socket. For the E-Class AMG, you will need a 13/32" socket.

At this point, you will be exposed to gas fumes and possibly fuel leaks. It is imperative that you aren't near any static electricity, smoke, or fire. Make sure to work in a well-ventilated area and have access to a fire extinguisher.

Remove the pump

To remove the fuel pump, you must first expose it. Start by accessing the rear door and lifting up the bottom of the passenger seat. The seat will snap at the front edge and will pop out with force. Once the seat is out, remove the protective liner and metal lid on top of the fuel pump assembly. This will expose six bolts; use your ratchet and socket to remove those.

There are a few details you must know before removing the fuel pump. These are the components that make up the fuel pump assembly:

• Fuel line: rubber black hose
• Wiring connector: white plastic wiring harness
• Holding Brackets: two metal rods that hold the fuel pump in place

Use the needle-nosed pliers to unclip the wiring harness, then use the flat-head screwdriver to unlock the fuel line and slide it off the pump. Lastly, use your fingers to snap off the holding brackets, then you can slide the fuel pump out of its housing. Remember that at this point, some fuel may leak out, so be prepared with a shop rag or a small bowl.

Install the new pump

Now that you have removed the old fuel pump, you can install the new one.

First, connect the wiring harness. This is the white plastic wiring harness that you unclipped with the needle-nose pliers when removing the old pump.

Next, replace the six bolts that hold the cover in place. These are the six 13/32" bolts that you removed with your ratchet and socket.

Finally, replace the protective liner. This is the protective liner and metal lid that you removed to expose the six bolts.

Once you have installed the new pump, fill the fuel tank with about 2 gallons of fuel before attempting to start the car. Once you are sure that the fuel pump is operating normally, fill the remainder of the fuel tank and check for leaks.

Test the new pump

To test your new fuel pump, you should first ensure that you have reconnected the wiring harness and tightened the threaded collar. Then, fill the fuel tank with about 2 gallons of fuel before attempting to start the engine. Once you are sure that the fuel pump is operating normally, fill the remainder of the fuel tank and check for leaks.

If you are still experiencing issues with your fuel pump, you can test the fuel pump relay with a multimeter. First, turn off your vehicle and remove the key from the ignition. Locate the fuel pump relay in your vehicle's fuse box, which is usually located underneath the hood near the front of your vehicle. Pull the relay straight out from the fuse box to remove it.

Next, clean the relay prongs with a wire brush to remove any rust or corrosion. You can also try cleaning the terminal ports on the fuse box with the wire brush. If necessary, wet a cloth with an electrical contact cleaner and rub it into the prongs.

Now, read the circuit diagram on the relay to know which prongs to connect the power and multimeter to. Set your multimeter to the ohm setting and attach jumper wires to the terminals on your vehicle's battery. Connect the jumper wires to the positive and negative relay terminals.

Listen for a clicking sound when you attach the power to know if the relay still works. If you don't hear a clicking sound, unclip the wire from the prong and touch the end of the jumper wire to the prong repeatedly so you can hear the clicking noise.

Finally, hold the multimeter probes against the other two prongs on the relay. Check the multimeter for a 0 reading to know that the relay still functions. If the reading is greater than 0, the circuit inside the relay is faulty.

Frequently asked questions