Checking Fuel Pressure: Audi A4 2009 Guide

If you are experiencing issues with your Audi A4 2009 such as a loss of power, engine performance problems, or difficulty starting the car, you may need to check the fuel pressure. Fuel pressure issues can cause a range of problems, from a simple sputter when going uphill to a complete loss of engine power. Checking the fuel pressure can help identify whether the issue lies with the fuel pump, fuel filter, fuel lines, or another component of the fuel delivery system. While a fuel pressure test can be done at home with the right tools, it is important to prioritize safety when working with fuel.

Check the fuses and relays before replacing parts

To check the fuel pressure in your 2009 Audi A4, you will need to check the fuses and relays before replacing any parts. This is because a loss of fuel pressure can be caused by a number of issues, and it is important to identify the root cause before taking action.

The first step is to locate the fuse boxes. Your Audi A4 has three fuse boxes: one under the hood, one in the passenger compartment, and a relay box in the passenger compartment. The fuse boxes are located behind covers on the left and right sides of the dash panel, and the relay box is in the passenger compartment. Once you have located the fuse boxes, you can begin your checks.

For the 2009 model, the fuses you should be checking are the 5A, 10A, 15A, 20A, 30A, 35A, 40A, 60A, and 110A fuses. These fuses correspond to various electrical circuits in the vehicle, including the engine management system, engine control module, fuel pump control module, and power steering.

To check the fuses, you will need to remove the fuse box covers and inspect the fuses for any signs of damage or corrosion. A blown fuse will typically have a broken wire or a burnt appearance. If you find any damaged fuses, you will need to replace them with new ones of the same amperage.

In addition to checking the fuses, you should also verify the condition of the relays. Relays are electrical switches that control various functions in the vehicle. To check the relays, you will need to locate the relay box in the passenger compartment and remove the cover. Then, inspect the relays for any signs of damage or corrosion. If any relays appear faulty, you can try swapping them with other relays of the same type to see if that resolves the issue.

By checking the fuses and relays before replacing parts, you can narrow down the potential causes of the low fuel pressure issue and make a more informed decision about the necessary repairs. This can save you time and money, as well as help ensure that the correct issue is addressed the first time.

Check for a blown fuse or faulty relay at pin 3

If you're experiencing issues with your 2009 Audi A4's fuel pressure, there are a few things you can check to diagnose the problem. One potential issue could be a blown fuse or faulty relay at pin 3, which is related to the fuel pump control module. Here's a step-by-step guide to help you check for this issue:

First, locate the fuel pump control module. It should be in the engine compartment, specifically in the box in the centre of the plenum chamber. Once you've found it, you'll want to refer to the fuel pump control module's five wires. Identify pin 3, which should be a B+ with the key on. This power source comes from fuse 28 and the ECM power supply relay.

Now, you'll want to check if you're receiving 12 volts at pin 3. If you're not getting the expected voltage, this could indicate a blown fuse or a faulty relay. To confirm this, you should check the fuse box and inspect fuse 28. A blown fuse will need to be replaced. If the fuse looks intact, the issue may lie with the relay, which may need to be repaired or replaced.

It's important to note that fuse boxes can vary depending on the year of your Audi A4. For the 2009 model, the fuse box is typically located in the engine compartment, either in the centre of the plenum chamber or on the switchgear fuse board. Be sure to consult a repair manual or a trusted mechanic if you're unsure about the location of your fuse box or the procedure for checking and replacing fuses and relays.

Additionally, remember to exercise caution when working with any electrical components in your vehicle. Ensure the car is turned off, and if you're uncomfortable or unfamiliar with automotive electrical systems, it's best to seek professional assistance.

Check for corrosion in the plug

To check for corrosion in the plug of your 2009 Audi A4, you will first need to locate the plug. The plug is accessed under the rear seat. Pull up on the front of the seat and then remove the seat. This should expose three screws that hold a cover in place; remove these screws and you will be able to see the plug.

Once you have located the plug, you can begin to inspect it for signs of corrosion. Corrosion may present as a green or white substance on the spark plug, or as rust. Corrosion can cause engine misfires, reduced gas mileage, slow acceleration, and trouble starting the engine. If you notice any of these issues, it is important to check your spark plugs for corrosion.

If you notice any corrosion on the spark plug, it is important to clean it or replace it. You can use an appropriate cleaning agent to remove the corrosion, or consult a mechanic for guidance.

Additionally, it is important to address the underlying cause of the corrosion to prevent it from recurring. Corrosion may be due to a variety of factors, including a dirty air filter, excessive driving at low speeds, a rich fuel-air mixture, or idling your vehicle for too long. In some cases, corrosion may be due to more serious issues, such as worn pistons or valve guides, or a coolant leak. If you suspect any of these issues, it is important to consult a mechanic for further diagnosis and repair.

Check the camshaft and follower for wear

To check the camshaft and follower for wear on your 2009 Audi A4, you will need to remove the cam follower and inspect it for signs of wear. This is a critical component in your car's fuel system, serving as a barrier between the high-pressure fuel pump and the camshaft lobe that drives it.

Step 1: Locate the Cam Follower

The cam follower is located near the high-pressure fuel pump and the camshaft lobe. You will need to remove any necessary components to access this area, such as the fuel pump and its cover.

Step 2: Remove the Cam Follower

Once you have located the cam follower, you will need to remove it carefully. Make sure to note how it is positioned for reinstallation.

Step 3: Inspect the Cam Follower for Wear

Visually inspect the cam follower for any signs of wear or damage. Look for areas where the cam follower has worn down, especially if it has worn through the black coating. Check if the cam follower has worn down to the base metal. If there are no signs of wear and the coating is intact, the cam follower is likely in good condition.

Step 4: Decide on Replacement

If the cam follower shows signs of wear, it is recommended to replace it. Even if there is no visible damage, some owners choose to replace the cam follower as part of regular maintenance to avoid the costly consequences of a worn-out cam follower. The cam follower is not an expensive part, and replacing it can provide cheap insurance against potential damage to other engine components.

Step 5: Check the Camshaft

While you have access to the camshaft, it is a good idea to inspect it for any signs of wear or damage. Look for areas of premature wear, especially on the lobe that drives the high-pressure fuel pump. If the camshaft shows signs of wear, it may need to be replaced as well.

Step 6: Reinstall or Replace Components

If the cam follower and camshaft show no signs of excessive wear and are within acceptable limits, you can reinstall them. If you choose to replace the cam follower or camshaft, use genuine OEM parts or high-quality aftermarket alternatives. Ensure all components are properly secured and reassembled.

It is recommended to check the cam follower regularly, with some owners checking it every 10,000 to 20,000 miles or every year or two. This proactive approach can help prevent unexpected failures and costly repairs.

Check the fuel tank or rear seat for removal

To check the fuel tank or rear seat for removal, you will first need to pull up on the front of the rear seat to release the connectors. If your Audi A4 has rear seat heaters, carefully lift the rear seat bottom to find the wires and disconnect them. Pull the seat bottom out of the car and set it aside to allow for easier access to the pump area.

Next, on the passenger side, find the pump cover where the back seat cushion would normally sit. Remove the three Phillips-head screws and take off the plate. You should now be able to see the fuel pump assembly head.

At this point, you can disconnect the pump by first disconnecting the fuel filter located in the front of the passenger side wheel well. Use a bucket to collect the fuel as it releases the pressure. Then, disconnect the power connector from the fuel pump head. Push down on the gas line fitting and, using a set of modified needle-nose pliers or a couple of small flat-tip screwdrivers, squeeze the side catches and pull up on the fuel line to disconnect it from the fuel pump head.

Finally, you can remove the pump by first marking the fuel pump ring with a Sharpie marker to indicate its position when putting it back together. Then, using a fuel tank wrench, turn the fuel pump ring counterclockwise to release it from the tank. Alternatively, you can use a flat-tip screwdriver and a hammer to lightly tap the ring until it releases. Pull up on the pump head slightly to reveal the rest of the pump, which sits inside the tank.

Frequently asked questions