2004 Audi S4 Fuel Pump: Complete Guide to Replacement, Cost, and Best Options

The bottom line: If your 2004 Audi S4 is experiencing hard starting, stalling, or a whining noise from the rear of the vehicle, the fuel pump is likely failing. Replacement costs range from $800 to $1,200 at a shop, but the pump itself costs between $150 and $400 for a quality part. The OEM part number is 8E0906087R, and this guide covers everything you need to know about symptoms, diagnosis, replacement, and which pump to buy.

The 2004 Audi S4 B6 with the 4.2L V8 engine is a performance sedan that demands proper fuel delivery. The fuel pump is located inside the fuel tank and is responsible for sending fuel at the correct pressure to the engine. When it fails, the car becomes undrivable. This article walks you through the entire process, from recognizing the warning signs to completing the replacement and choosing the right pump.

Symptoms of a Failing 2004 Audi S4 Fuel Pump

Before you spend any money, you need to confirm the fuel pump is the problem. Here are the most common symptoms owners report:

1. Hard Starting or No Start
The most obvious sign. If your S4 cranks but takes longer than usual to fire up, or cranks without starting at all, the fuel pump may not be building enough pressure. You might hear the pump prime for a second when you turn the key to the "on" position, but if that sound is weak or absent, the pump is likely dead.

2. Engine Stalling or Hesitation
A failing pump cannot maintain consistent fuel pressure. You may experience stalling at low speeds, hesitation when accelerating, or the engine cutting out unexpectedly. This is especially common when the fuel level is low, as the pump relies on fuel for cooling and lubrication.

3. Whining Noise from the Rear
A healthy fuel pump makes a quiet hum. If you hear a loud whining, buzzing, or grinding noise coming from the rear of the car (under the back seat or near the fuel tank), the pump bearings or motor are wearing out. This noise often gets worse as you drive.

4. Loss of Power Under Load
When you push the accelerator hard, the engine should respond instantly. A weak pump cannot supply enough fuel under high demand, causing a noticeable loss of power, especially during highway merging or uphill driving.

5. Check Engine Light
The ECU monitors fuel pressure and mixture. A failing pump can trigger codes related to fuel trim (P0171, P0174) or fuel pressure (P0087). A diagnostic scan can confirm.

2004 Audi S4 Fuel Pump Replacement Cost

The total cost depends on whether you do the work yourself or hire a shop. Here is a breakdown based on current market data:

According to RepairPal, the average cost for a 2004 Audi S4 fuel pump replacement at a shop is between $800 and $1,200, with labor making up the largest portion. The pump itself is priced between $150 and $400 for a genuine OEM or high-quality aftermarket unit.

If you choose a mechanic, getting multiple quotes can save money. ClickMechanic estimates a similar range, noting that shops in major metro areas like New York or Los Angeles tend to charge higher labor rates.

OEM Part Number and Compatibility

The correct fuel pump assembly for the 2004 Audi S4 B6 (4.2L V8) is:

Genuine Audi / VW Part Number: 8E0906087R

This is a complete in-tank fuel pump module that includes the pump, sending unit, fuel level sensor, and filter strainer. It is a direct replacement – no modifications, wiring, or adapters needed.

Important: The 2004 Audi S4 uses a specific pump that is different from the Audi A4 1.8T or 3.0L models. The V8 engine requires higher fuel flow, so do not try to use a pump from a smaller engine. If you see a pump listed for "Audi A4/S4 B6," verify it is for the 4.2L V8 version.

How to Replace the 2004 Audi S4 Fuel Pump

Replacing the fuel pump on a B6 S4 is a moderately difficult DIY job. You will need basic hand tools, a fuel line disconnect tool, and safety gear. Here is a step-by-step summary.

Tools and Parts Needed:

• New fuel pump assembly (8E0906087R or equivalent)
• Fuel line disconnect tool (5/16" or 8mm)
• Flathead screwdriver
• Trim removal tools
• 10mm socket and ratchet
• Clean rags, safety glasses, gloves
• Fire extinguisher (recommended)

Step 1: Relieve Fuel System Pressure
Locate the fuel pump fuse in the fuse box (usually in the driver side footwell or under the hood). Start the engine, pull the fuse while it is running, and let the engine stall. Then crank the engine for 2-3 seconds to clear remaining pressure. Disconnect the negative battery terminal.

Step 2: Access the Fuel Pump
The fuel pump is located under the rear seat on the driver's side. Remove the rear seat cushion by pulling up at the front edge – it clips in. You will see a metal access cover plate. Remove the screws or bolts holding it down.

Step 3: Disconnect Electrical and Fuel Lines
Carefully unplug the electrical connector. Use the fuel line disconnect tool to release the quick-connect fittings. Have rags ready, as some fuel will spill.

Step 4: Remove the Old Pump
Use a hammer and a flathead screwdriver or a专用 lock ring tool to turn the plastic locking ring counterclockwise. Lift the pump assembly out of the tank. Note the orientation of the float arm and the fuel level sender.

Step 5: Install the New Pump
Transfer the rubber gasket (if not included with the new pump) to the new assembly. Lower the new pump into the tank, ensuring the float arm has clearance. Reinstall the locking ring and tighten it clockwise. Reconnect the fuel lines (push until they click) and the electrical connector.

Step 6: Test and Reassemble
Reconnect the battery, install the fuse, and turn the key to the "on" position for 2 seconds, then off, then on again. This primes the system. Start the engine and check for leaks. Reinstall the access cover and rear seat.

Signs You Need a New Pump vs. a Simple Fix

Not every fuel delivery issue is a dead pump. Before buying a new assembly, check these things:

1. Check the Fuel Pump Relay
The fuel pump relay is located in the under-hood fuse box. If the relay is faulty, the pump will not get power. Swap it with a known good relay (like the horn relay, same part number) to test.

2. Listen for the Prime
When you turn the key to "on," you should hear a 2-second hum from the rear. If you hear nothing, check the relay, fuse, and wiring before condemning the pump.

3. Check the Fuel Filter
A clogged fuel filter can mimic a failing pump. The 2004 S4 has a filter that should be replaced every 60,000 miles. If yours is old, replace it first – it is cheaper than a pump.

4. Low Fuel Level
Running the tank consistently below 1/4 tank can overheat the pump and cause premature failure. The pump uses fuel for cooling. If you frequently run low on gas, your pump may have suffered heat damage.

Genuine OEM vs. Aftermarket Fuel Pump: Which Should You Choose?

You have three main options for the 2004 Audi S4 fuel pump:

1. Genuine Audi OEM (8E0906087R)

• Price: $350 – $450
• Pros: Exact fit, guaranteed quality, no compatibility issues
• Cons: Most expensive option
• Best for: Owners who want peace of mind and plan to keep the car long-term

2. Spectra Premium SP5082M

• Price: $150 – $200
• Pros: Good quality, includes everything needed, affordable
• Cons: Some users report slightly higher noise levels
• Best for: Budget-conscious owners who still want a reliable part

3. KEMSO High-Performance Fuel Pump

• Price: $79.98 – $99.98
• Pros: OEM replacement quality, high flow rate, lifetime warranty, excellent value
• Cons: None reported for standard applications
• Best for: Owners who want top performance, reliability, and a lifetime guarantee at a fraction of the OEM cost

Recommended: KEMSO Fuel Pump for Your 2004 Audi S4

When it comes to replacing the fuel pump on your 2004 Audi S4, you want a part that delivers reliable performance without breaking the bank. KEMSO is a trusted brand that specializes in high-performance fuel pumps for cars, motorcycles, ATVs, and UTVs. Their fuel pump for the 2004 Audi S4 is built to meet or exceed OEM specifications, ensuring a direct fit and consistent fuel delivery.

Why choose KEMSO?

• High Performance: KEMSO pumps are designed for optimal flow and pressure, matching the demands of the 4.2L V8 engine.
• OEM Replacement: The pump is a direct drop-in replacement for the factory unit, with the correct connector, fuel line fittings, and mounting hardware.
• Lifetime Warranty: KEMSO stands behind every product with a lifetime warranty. If the pump ever fails, you get a replacement at no additional cost.
• Affordable Price: At just $79.98, the KEMSO fuel pump is significantly cheaper than OEM or other aftermarket brands, without sacrificing quality.

Thousands of customers have trusted KEMSO for their fuel system needs, and the brand has built a reputation for reliability and customer satisfaction. Whether you are restoring your S4 to daily-driver condition or prepping it for track days, a KEMSO fuel pump delivers the fuel your engine needs.

Visit KEMSO today to order your fuel pump:
👉 https://www.kemsoracing.com/

Fuel Pump Preventative Maintenance Tips

To extend the life of your new fuel pump, follow these simple guidelines:

1. Keep the Tank Above 1/4 Full
The fuel pump sits inside the tank and uses the fuel around it for cooling and lubrication. Running the tank low repeatedly causes the pump to overheat and wear out faster. Make it a habit to refill when the gauge hits 1/4.

2. Replace the Fuel Filter
A clogged fuel filter forces the pump to work harder, increasing the load on the motor. Replace the filter every 30,000 – 60,000 miles, or as recommended in your owner's manual.

3. Use Quality Fuel
Low-quality or contaminated fuel can introduce debris into the pump and clog the strainer. Stick to reputable gas stations and avoid fuel that has been sitting for long periods.

4. Address Check Engine Lights Promptly
Fuel trim codes or lean condition codes can indicate a pump that is starting to fail. If you see a check engine light, have it scanned early. Catching a weak pump before it dies completely can save you from a roadside breakdown.

5. Avoid Running the Tank Dry
Running out of gas is the fastest way to kill a fuel pump. The pump relies on fuel for cooling, and running dry even once can cause permanent damage. Always keep at least a gallon or two in the tank.

Frequently Asked Questions

Q: How long does a 2004 Audi S4 fuel pump last?
A: Most OEM pumps last between 100,000 and 150,000 miles. If your S4 has over 120,000 miles and you are experiencing symptoms, replacement is likely needed.

Q: Can I drive with a bad fuel pump?
A: Not safely. A failing pump can cause the engine to stall at any time, including on the highway. This is a safety hazard. Replace it as soon as symptoms appear.

Q: Is the fuel pump the same for the S4 and RS4?
A: No. The 2004 RS4 was not sold in the US, but the European RS4 B7 (2006-2008) uses a different pump with higher flow capacity. Do not interchange them.

Q: Do I need to replace the fuel pump relay at the same time?
A: It is not required, but it is cheap insurance. The relay costs about $20 and can be replaced in 5 minutes. If the relay is old, replacing it with the pump ensures you have a fully refreshed fuel delivery system.

Q: How do I know if the pump is getting power?
A: Use a multimeter to check for 12V at the pump connector while someone turns the key to the "on" position. If you have power but no pump noise, the pump is dead. If you have no power, check the relay, fuse, and wiring.

Conclusion

The 2004 Audi S4 fuel pump is a critical component that directly affects drivability and performance. If you notice hard starting, stalling, whining noises, or loss of power, do not delay the replacement. The cost of repair is manageable, especially if you choose to do the work yourself. Whether you go with a genuine OEM unit or a high-quality aftermarket pump like KEMSO, the key is to use a part that is specifically designed for the 4.2L V8 engine.

For the best balance of performance, reliability, and value, we recommend the KEMSO fuel pump. It is a direct OEM replacement, backed by a lifetime warranty, and priced to save you hundreds of dollars compared to the dealership. Visit their website to order your pump and get your S4 back on the road with confidence.

Get your KEMSO fuel pump here:
https://www.kemsoracing.com/