Replacing Audi A4 Fuel Relay: Step-By-Step Guide

If you're looking to replace the fuel relay on your 2005 Audi A4 convertible, you'll first need to locate the fuel pump relay. This can be found in the relay panel under/behind the engine ECU. The fuel pump relay is one of two relays numbered 614, and you can identify it as the one on the left. Once you've identified the fuel pump relay, you can try swapping the two relays over to see if that fixes the problem. If not, you may need to replace the relay or seek further diagnostics from a mechanic.

Fuel pump relay location

The fuel pump relay and fuel pump fuse should be in the fuse box or power distribution box under the hood of your Audi A4.

To access the fuel pump relay, you will need to remove the side fuse box cover, take out the lower dash, and then unscrew the side fuse box. The relay is located under the driver's side dash knee panel. Specifically, it is under the left knee, in the far left position.

The fuel pump relay is labelled '614' and is the far left one. It has four prongs and is medium grey in colour.

Fuel pump fuse location

The fuel pump relay and fuse are located in the fuse box or power distribution box under the hood.

To replace the fuel pump relay in your 2005 Audi A4 convertible, you will first need to locate the fuse box. The fuse box is located in the engine compartment, on the right side, behind a protective lining. Once you have located the fuse box, you can follow these steps:

• Open the fuse box by releasing the locking tabs or removing any screws securing it.
• Locate the fuel pump relay. It should be labelled on the fuse box diagram, which is usually located on the inside of the fuse box lid.
• Once you have located the fuel pump relay, remove it by pulling it straight out or by releasing any locking tabs or clips holding it in place.
• Insert the new fuel pump relay into the vacant slot, ensuring that it is securely seated.
• Close the fuse box and secure it by engaging the locking tabs or replacing any screws that were removed.

It is important to note that the fuel pump relay is different from the fuel pump fuse. The fuel pump fuse is also located in the fuse box, and it is responsible for protecting the fuel pump circuit from electrical surges. If the fuel pump fuse blows, it will need to be replaced to restore power to the fuel pump.

In addition to locating the fuel pump relay and fuse, you may also need to access the fuel pump itself, which is located in the fuel tank. To replace the fuel pump, you will need to remove the fuel tank and disconnect the fuel lines and electrical connectors before installing the new pump.

Fuel pump relay replacement

To replace the fuel pump relay on a 2005 Audi A4 convertible, you'll first need to locate the relay. According to Audi mechanics, the fuel pump relay is located in the relay panel under/behind the engine ECU.

• Locate the engine ECU: The ECU (Engine Control Unit) is typically located in the engine compartment, often near the firewall or on the passenger side of the vehicle. It is a small, rectangular box with multiple connectors and may be labelled with "ECU" or "ECM" (Engine Control Module).
• Access the relay panel: The fuel pump relay is located under or behind the ECU. You may need to remove any covering or panels to access the relay panel.
• Identify the fuel pump relay: In the relay panel, look for a relay labelled as "Fuel Pump Relay" or "Fuel Lift Pump Relay." It may be numbered as well, so refer to your vehicle's relay diagram to identify the correct relay.
• Remove the old relay: Carefully pull out the old fuel pump relay from the relay panel. It should come out easily, but be gentle to avoid damaging any connectors or neighbouring relays.
• Insert the new relay: Obtain a new fuel pump relay that is compatible with your vehicle. Ensure it is the correct type and amperage rating. Align the new relay with the vacant slot in the relay panel and firmly push it into place.
• Test the fuel pump: Once the new relay is installed, turn the ignition key to the "On" position. You should hear the fuel pump priming for a few seconds. If not, recheck your connections and ensure the new relay is installed correctly.

It is important to note that working on fuel systems can be dangerous due to the flammable nature of fuel. Always exercise caution and refer to safety guidelines when working on any part of the fuel system. Additionally, ensure that you are using the correct tools and safety equipment for the job.

If you are unsure about any part of the process, it is best to consult a qualified mechanic or seek advice from a trusted Audi forum or community.

Fuel pump relay voltage

The fuel pump relay is responsible for supplying power to the fuel pump. The ideal voltage for the fuel pump is 14 volts, but some pumps can work with a voltage as low as 12 volts.

If you are experiencing issues with your fuel pump, it is important to check the voltage at the fuse using a voltmeter. This can be done with the key in the "On" position or while cranking the engine. The fuel pump will initially activate for a few seconds when the key is turned to the "On" position and will then shut off, but it will reactivate during cranking.

If you are not getting the correct voltage at the fuse, there may be an issue with the wiring or the fuel pump relay. In this case, you can try re-wiring the fuel pump to ensure it is receiving a dedicated voltage supply directly from the battery. This can help to prevent voltage fluctuations that may affect the fuel pump's performance.

To re-wire the fuel pump, you will need to locate the fuel pump's wiring and find the 12V supply wire from the ECU to the fuel pump. Once located, cut this wire to create two separate halves: one running to the fuel pump and the other to the factory ECU.

Next, you will need a four-prong relay with at least 14-gauge wiring. Connect pin 85 of the relay to the 12V supply wire from the ECU that you previously cut. This will energize the relay. Then, connect pin 86 to a good ground on the vehicle, ensuring that you use appropriately sized wire to avoid burning up the relay.

After that, run a dedicated wire from the battery to pin 30 on the relay. Finally, connect pin 87 to the factory wire that you cut, which runs to the fuel pump.

By performing this modification, you will ensure that the fuel pump receives a consistent and clean voltage supply directly from the battery, improving its performance and efficiency.

Fuel pump relay corrosion

Corrosion on the fuel pump relay is a common issue that can cause serious problems for your car. The fuel pump relay is an essential component of your car's electrical system, controlling the power to the fuel pump, which pressurises the fuel system. Corrosion on the relay can cause issues with the flow of electricity to the fuel pump, which can lead to start-up issues and even cause the engine to stall.

To diagnose a faulty fuel pump relay, you can start by locating the relay in the fuse box in the engine bay. It is cube-shaped and connects to prongs like an electrical plug. Once located, you can disconnect the relay and inspect the terminals and sockets for signs of corrosion. Remember to wear gloves and eye protection when handling the relay. If you find corrosion, you can attempt to clean it using electrical contact cleaner.

If cleaning the relay does not solve the issue, you may need to replace the fuel pump relay. This process can be complex, as the fuel pump relay is often soldered in place. Therefore, it is recommended that you consult a professional mechanic to avoid causing further issues.

Frequently asked questions