Replacing Fuel Pump Relay In Bmw E46: Step-By-Step Guide

If you're looking to change the fuel pump relay in your BMW E46, you'll first need to locate it. The fuel pump relay is located behind the glove box, above the right shock tower, or behind the passenger side rear door panel. Once you've found it, you can then proceed to change the relay. It's important to note that you should disconnect the battery before beginning any work on your vehicle's electrical system. Additionally, when prying out trim panels, switches, or electrical accessories, use a plastic prying tool or wrap a screwdriver tip with masking tape to avoid marring the trim.

Locating the fuel pump relay

It is worth noting that the location of the fuel pump relay may vary depending on the model of your BMW E46. For example, on the M3 Coupe, the fuel pump relay is located right above the right shock tower, while on the M3 Convertible, it is believed to be placed behind the passenger-side rear door panel.

Removing the glove box

To access the fuel pump relay, you will first need to remove the glove box. Here is a step-by-step guide on how to do this:

• Open the glove box.
• Remove the five Phillips-head screws from the glove box.
• Lower the glove box, disconnect the flashlight electrical connector, and detach the wiring harness from the back.
• Remove the glove box from the dashboard.
• Lower the plastic trim panel and disconnect the footwell light electrical connector.
• Remove the trim panel from the vehicle.

Now that the glove box has been removed, you can access the fuel pump relay. It is located behind the fuse box and can be a bit tricky to reach. There should be a couple of Torx screws holding the fuse box in place. Remove these screws and push the fuse box out of the way to reveal the relays. The fuel pump relay is one of the light green relays.

Testing the fuel pump relay

The fuel pump relay is located behind the glove box in the control module rack. To access it, you will need to remove the glove box.

The first step in testing the relay is to verify it is getting power. The relay gets power at two of its four terminals; at terminal 8 from the E-box fuse block, and at terminal 6 from the glove box fuse block.

Use a 12V test light or multimeter to verify that the relay is receiving power. The relay is receiving power if the test light lights up for approximately one second when the key is turned to the second ("start") position.

If the test light confirms there is power at the pump, proceed to the next step. If the test light shows there isn’t power at the pump, the next step is to check the fuses and the relay.

If you determine power is not being supplied to the pump, then you will have to check the fuse and the relay to find the culprit. Usually, one (or both) has failed and will need to be replaced.

Checking the fuel pump fuse is simple. It is located in the glove box. Checking the fuel pump relay is a little more time-consuming. The glove box will have to be removed and the control module rack lowered from the dashboard to gain proper access to the relay. Once the relay is removed, you can use a 12V test light or multimeter to verify that it is receiving power. Finally, you will need to "jump" the relay with a piece of wire to confirm the relay is bad.

If neither of the fuel pump fuses are blown, or if you still do not have power at the fuel pump after replacing a blown fuse, then most likely, the power issue is due to a faulty relay.

Replacing the fuel pump relay

The fuel pump relay in a BMW E46 is located behind the glovebox. To access it, you will need to remove the glovebox and the fusebox. There are a few torx screws holding the fusebox in place, so you will need a torx screwdriver to remove them. Once the fusebox is removed, you will see the relays behind it. There should be three lime-green relays: one for the horn, one for the fuel pump, and one for the lights.

Before replacing the fuel pump relay, you should check if the fuel pump is working by lifting the rear seats and turning on the ignition. If the fuel pump is functioning correctly, you should hear a constant buzzing noise under the insulation for about 30 seconds. If the fuel pump is not working, you may need to replace it.

To replace the fuel pump relay, start by disconnecting the battery. Then, locate the fuel pump relay behind the glovebox and fusebox. Remove the old relay by pulling it out of its socket. Insert the new relay into the empty socket, making sure it is securely connected. Once the new relay is in place, you can reconnect the battery and turn on the ignition to test if the fuel pump is now working.

If you are unsure which relay to replace, you can try swapping the fuel pump relay with another relay of the same colour. If the problem persists, then you may need to replace the fuel pump itself. This is located under the rear seat on the driver's side. To access it, remove the rear seat and the access panel to the fuel tank. Disconnect the fuel lines and electrical connector from the fuel pump, then unscrew the fuel pump from the fuel tank. Install the new fuel pump by screwing it into the fuel tank and reconnecting the fuel lines and electrical connector.

When working on your vehicle, always take the necessary safety precautions. Ensure you are wearing protective gear, including eye protection and gloves. It is also important to disconnect the battery before beginning any electrical work. Additionally, be mindful of fuel spills when working with the fuel system, and always dispose of fluids and parts properly.

Testing the fuel pump

One way is to use a multimeter to check for power running to the pump. Insert the multimeter leads into the harness connector at the fuel pump and turn the ignition to the "on" position. If the voltage drops from 12V to 0V, then there may be an issue with the relay or the pump itself.

Another method is to perform a fuel pressure test. Attach a fuel pressure gauge to the Schrader valve on the fuel rail. When the car is idling, the pressure should be around 3.5 bar (50.8 PSI). After switching off the car, you can observe how the pressure drops over time. A significant drop in a short time may indicate an issue with the fuel pump or a leak in the system.

You can also try clamping the return hose from the fuel filter after priming the fuel rail to see if that impacts the pressure. If clamping the hose slows down the pressure loss, then the issue may lie with the check valve in the fuel pump or a restriction in the delivery side.

Additionally, you can test the fuel pump by connecting it directly to a battery outside of the tank. If the pump works, then the issue may lie elsewhere, such as with the relay or a fuse.

It is important to note that fuel pump issues can be complex, and it is recommended to replace the fuel pump if your car is over eight years old.

Frequently asked questions