Replacing The Fuel Pump Relay In Your E46: A Step-By-Step Guide

The fuel pump relay in the BMW E46 is located behind the glovebox, which can be removed to expose the relays. The fuel pump relay is green in colour and is usually the first in a bank of four. However, in some models, it may be located elsewhere, such as behind a trim panel near the fuel pump or in the boot. It is important to consult a wiring diagram or a repair manual to correctly identify the fuel pump relay and perform any necessary maintenance or replacements.

How to locate the fuel pump relay in an E46

Locating the fuel pump relay in an E46 is a crucial step in performing maintenance or repairs on your BMW. Here is a detailed guide to help you find it:

Step 1: Locate the Glove Box

The first step is to identify the glove box or dashboard compartment of your E46. This is usually located on the passenger side of the vehicle, below the dashboard.

Step 2: Remove the Glove Box

Removing the glove box will give you access to the area behind it, where the fuel pump relay is typically located. The process of removing the glove box may vary slightly depending on your specific E46 model, but it usually involves unscrewing or unclipping the glove box and carefully disconnecting any electrical connectors attached to it. Make sure to have a safe place to store the items inside the glove box temporarily.

Step 3: Identify the Fuel Pump Relay

Once the glove box is removed, you should see a bank of relays and fuses. The fuel pump relay is usually located in this area. It may be green in colour, but this can vary depending on the model year and region.

On some E46 models, the fuel pump relay is the first or leftmost relay in the bank. However, on other models, it may be located elsewhere, such as behind a trim panel near the fuel pump or in the boot. If you are unsure, refer to a diagram or schematic specific to your E46 model, or seek advice from a BMW specialist.

Step 4: Confirm with Voltage Testing

To confirm that you have located the correct relay, you can perform voltage testing. Disconnect the relay and turn the ignition to the "ON" position. If you can no longer hear the fuel pump priming, you have likely found the fuel pump relay.

Additionally, you can use a digital volt-ohm meter (DVOM) to test the voltage at the fuel pump terminals. If the correct voltage is present but the pump does not activate, the fuel pump may be faulty and require replacement.

Step 5: Reassemble and Test

Once you have located and addressed any issues with the fuel pump relay, carefully reassemble the glove box and any other components you removed. Start the vehicle and observe whether the issues you were experiencing have been resolved. If not, you may need to consult a BMW mechanic or specialist for further diagnosis and repair.

How to test the fuel pump relay

To test the fuel pump relay of your BMW E46, you will need a multimeter. This device will allow you to check the resistance going through the relay's circuit. Here is a step-by-step guide on how to test the fuel pump relay:

Removing and Cleaning the Relay for Testing:

• Turn off your vehicle and remove the key from the ignition.
• Find the fuel pump relay in your vehicle's fuse box. The main fuse box is usually located underneath the hood near the front of your vehicle, but there may also be a smaller fuse box under the steering column inside your car. Pull the cover off the fuse box and look at the diagram to locate the fuel pump relay. It is usually coloured green or grey.
• Pull the relay straight out from the fuse box to remove it. Grab the relay firmly on either side and pull it straight up and out from the terminals of the fuse box. If the relay doesn't come out right away, try rocking it back and forth to loosen the connection.
• Clean the relay prongs with a wire brush. Hold the relay upside down so the prongs point up and firmly scrape them 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.

Testing the Relay's Resistance:

• Read the circuit diagram on the relay to know which prongs to connect the power and multimeter to. Look for the 2 points on the diagram that have a box in between them. These are the prongs that control the power and are usually labelled 85 and 86. The prongs that you need to test are labelled 30 and 87 and have a break in the line connecting them.
• Set your multimeter to the ohm setting. This setting will allow you to measure the resistance between the terminals on the relay to check if they are working properly.
• Attach jumper wires to the terminals on your vehicle's battery. Clip one of the jumper wires to the positive terminal and the other to the negative terminal.
• Connect the jumper wires to the positive and negative relay terminals. Flip the relay over so the prongs point up and clip the wire from the negative terminal to the terminal labelled 85, and the wire from the positive terminal to the pin labelled 86.
• Listen for a clicking sound when you attach the power. As soon as you attach both jumper wires, a switch on the internal circuit will close and make an audible noise. If you don't hear the clicking sound, the circuit inside the relay isn't working properly.
• Hold the multimeter probes against the other two prongs on the relay. Plug the multimeter probes into the ports on the bottom of the machine and hold either of the probes against one of the prongs labelled 30 or 87. Then, press the second probe against the last prong on the relay.
• Check the multimeter for a 0 reading to confirm that the relay still functions. When the circuit inside the relay has power, the prongs should not have any resistance between them. If the reading is greater than 0, the circuit inside the relay is faulty.

How to remove the fuel pump relay

To remove the fuel pump relay on a BMW E46, you will first need to locate the relay. The fuel pump relay is typically located behind the glovebox, although its exact position may vary depending on the model of your E46.

Once you have located the fuel pump relay, which should be light green in colour, you can proceed to remove it. Here is a step-by-step guide:

• Open the glovebox and remove all items from within.
• Locate the relay panel, which is held in place by a 10mm panel support fastener.
• Remove the 10mm panel support fastener using a socket set.
• Pull the relay panel out of the top clips and pull it down.
• Identify the fuel pump relay. It should be light green and may be labelled or marked.
• Remove the fuel pump relay from the relay panel.
• If necessary, you can now test the relay or replace it with a new one. Ensure that any replacement relay is compatible with your vehicle.

It is important to exercise caution when working on your vehicle, especially when dealing with electrical components. Always disconnect the battery before beginning any work on the electrical system. Keep yourself and your surroundings protected by wearing appropriate safety gear, such as gloves and eye protection.

How to replace the fuel pump relay

Step 1: Locate the Fuel Pump Relay

Before you can replace the fuel pump relay, you must first locate it. The fuel pump relay is typically located behind the glovebox, but the exact location may vary depending on the model of your E46. For example, for a 2002 E46 318i Convertible, the fuel pump relay is not the first in the bank of four relays, as commonly believed, but rather the third.

Step 2: Access the Fuel Pump Relay

To access the fuel pump relay, you will need to remove the glovebox. This process may vary depending on your specific model, but generally involves removing screws and disconnecting wiring harnesses.

Step 3: Identify the Fuel Pump Relay

The fuel pump relay is typically green in colour, but again, this may vary depending on your model. It is important to properly identify the fuel pump relay before proceeding with the replacement.

Step 4: Disconnect the Fuel Pump Relay

Once you have located and identified the fuel pump relay, you will need to disconnect it. This typically involves unplugging the electrical connector from the relay.

Step 5: Obtain a Replacement Relay

It is important to obtain a suitable replacement relay that is compatible with your specific E46 model. This may involve consulting a parts specialist or referring to a parts diagram.

Step 6: Connect the Replacement Relay

Finally, connect the replacement relay in the same manner as the original relay was connected. Ensure that all electrical connections are secure before replacing any removed components and closing the glovebox.

Additional Notes:

• It is recommended to consult a repair manual or a trusted mechanic if you are unsure about any part of this process.
• Ensure that you take appropriate safety precautions when working on your vehicle, including wearing protective gear and disconnecting the battery before working on the electrical system.
• Keep in mind that vehicle models may vary, and the specific steps and locations may differ slightly from those described above. Always refer to the appropriate documentation for your specific model when performing any maintenance or repairs.

How to test the fuel pump

To test the fuel pump of a BMW E46, you will need a digital volt ohm-meter (DVOM) and a wiring diagram for your specific model. You can then follow these steps:

• Confirm that the fuel pump has received the correct voltage when commanded on by the fuel pump relay using the DVOM.
• If the correct voltage is present but the pump does not activate, the pump is likely faulty.
• Use the DVOM in conjunction with the wiring diagram to determine the correct terminals for testing.
• Access the terminals under the rear seat cushion, below the access panel.
• Start or attempt to start the engine. Fuel pressure should be 3.5 bar +/- 0.2 (50 psi +/- 3).
• Recharge the fuel system by cycling the key or running the fuel pump, noting the fuel pressure.
• Allow the fuel system to sit under pressure for 15 minutes. Pressure should drop no more than 0.5 bar in that time. If it drops, you could have a faulty fuel pump check valve or a leak in the fuel system.

Frequently asked questions