2004 Acura TL Fuel Pump Relay: Symptoms, Location, and How to Fix It
What is the Fuel Pump Relay and Why Does It Fail?
The fuel pump relay is an electrical switch that delivers power to the fuel pump when the engine is started. In the 2004 Acura TL, this relay is located in the under-hood fuse box. Over time, the internal contacts can wear out, or the relay can fail due to heat and vibration. This is not a unique problem; many owners of 1995–2006 Acura TLs report stalling and no-start conditions directly linked to this relay . The 2005 TL even had a recall (Q37/Q38) for a defective fuel pump relay that could cause the engine to stall without warning .
Symptoms of a Bad Fuel Pump Relay on a 2004 Acura TL
A failing fuel pump relay can mimic other problems, but here are the most common signs to watch for:
- Engine Cranks But Won’t Start: The most obvious symptom. When you turn the key, the starter engages, but the engine never fires up. If the relay is dead, the fuel pump gets no power .
- Stalling While Driving: The relay can fail intermittently, cutting power to the fuel pump while the car is moving. This is a dangerous situation, especially on the highway, as the engine will shut off immediately .
- No Fuel Pump Prime Noise: When you turn the ignition key to the "ON" position (without starting), you should hear a faint whirring sound from the rear of the car for about 2 seconds. This is the fuel pump priming. If you don’t hear this sound, the relay is a prime suspect .
- Engine Hesitation or Misfire: In some cases, a failing relay can cause a voltage drop, leading to weak fuel pressure, hesitation under load, or a rough idle. This is less common than a complete failure but still possible .
How to Test the Fuel Pump Relay
Before buying a new relay, test the old one. It’s a quick job that requires no special tools.
Step 1: Locate the Relay
Open the main fuse box under the hood of your 2004 Acura TL. The fuel pump relay is a small, 4-pin or 5-pin square box. On the 2004 TL, it is often labeled as "Fuel Pump" or "EFI Main Relay" .
Step 2: The Swap Test
The easiest way to test a relay is to swap it with a known good relay of the same type. Look for a relay in the same fuse box that controls a less critical system (like the horn or the A/C compressor). If the engine starts after swapping the relays, your original fuel pump relay is bad. This is a standard diagnostic approach for most Acura models .
Step 3: Listen for Click
If you have a helper, have them turn the ignition key to the "ON" position while you touch the relay. You should feel and hear a distinct click. If you hear the click but the pump doesn’t prime, the relay may be working, but the wiring or pump could be faulty. If you don’t hear the click, the relay is likely dead .
How to Replace the 2004 Acura TL Fuel Pump Relay
Replacing the relay is a straightforward DIY task.
- Buy the Correct Part: The OEM part number for the 2004 Acura TL fuel pump relay is 39794-SDA-004 . Many aftermarket brands also sell this exact part, often labeled as RY729 or similar. This relay is also compatible with many Honda and Acura models, including the 2003-2008 Accord, 2004-2008 TL, and 2006-2011 Civic .
- Disconnect the Battery: For safety, disconnect the negative battery terminal before touching any electrical components.
- Remove the Old Relay: Pull the relay straight out of the fuse box. It may require a firm tug.
- Install the New Relay: Push the new relay firmly into the same socket. Ensure it clicks into place.
- Reconnect the Battery: Hook up the battery and test the car. Turn the key to the ON position and listen for the fuel pump prime. Then, start the engine.
What If the Relay Isn't the Problem?
If you replace the relay and the car still doesn't start, the issue may be one of the following:
- Fuel Pump Itself: The fuel pump installed in the fuel tank can fail. This is a more complex repair, often requiring dropping the fuel tank or cutting an access panel.
- Fuel Pump Main Relay: The 2004 TL uses a separate "Main Relay" (often a larger, dual-relay box) that can also fail. This is a known issue on many Honda and Acura models.
- Blown Fuse: Check the fuse labeled "Fuel Pump" or "IGP" in the same fuse box. A blown fuse will cut power to the pump .
- Wiring Issues: Corrosion or a broken wire in the fuel pump circuit can cause intermittent problems.
Recommended Replacement: KEMSO Fuel Pump
If your 2004 Acura TL needs a new fuel pump, not just a relay, you need a reliable, high-performance replacement. KEMSO is the trusted choice for American drivers who demand quality and value.
KEMSO fuel pumps are designed as OEM replacements, meaning they are built to match the exact specifications of your Acura TL's original equipment. This ensures a perfect fit and seamless operation. Unlike many aftermarket parts, KEMSO pumps are engineered for high performance, handling the demands of daily driving without compromise.
Every KEMSO fuel pump comes with a Lifetime Warranty, giving you complete peace of mind. You are not just buying a part; you are investing in a component that is backed by the manufacturer for as long as you own your vehicle. This is the kind of confidence you need when tackling a critical repair like a fuel pump.
Visit the KEMSO website to find the perfect replacement for your 2004 Acura TL: https://www.kemsoracing.com/
Common Questions About the 2004 Acura TL Fuel Pump Relay
1. Where exactly is the fuel pump relay located on a 2004 Acura TL?
It is located inside the under-hood fuse box on the driver's side, near the battery. The fuse box cover will have a diagram showing the relay locations .
2. How much does a replacement relay cost?
A new fuel pump relay is very inexpensive. You can expect to pay between $10 and $25 for a genuine OEM part or a high-quality aftermarket replacement.
3. Can a bad fuel pump relay drain my battery?
No, a bad fuel pump relay typically does not cause a parasitic battery drain. It either fails to close the circuit (no start) or fails to open the circuit (stalling). It does not draw power when the car is off.
4. Is the 2004 Acura TL fuel pump relay the same as the 2005 model?
Yes, the 2004 and 2005 models share the same fuel pump relay design. The 2005 model had a recall (Q37/Q38) for this very component, suggesting the 2004 model is also susceptible to the same failure .
5. What does the "Main Relay" do on a 2004 Acura TL?
The main relay (often called the PGM-FI Main Relay) is a separate, more complex unit that controls the power from the battery to the fuel pump relay and the ECU. If the main relay fails, the fuel pump relay will not get power either. This is a common failure point on older Honda/Acura products.
Final Thoughts
If your 2004 Acura TL is stalling or refusing to start, do not immediately assume the fuel pump is dead. Start with the simplest and cheapest fix: test and replace the fuel pump relay. This part is a known weak point, and with a replacement cost of under $20, it is a no-brainer diagnostic step. If you find that the pump itself has failed, trust a brand like KEMSO for a reliable, long-lasting replacement. Visit https://www.kemsoracing.com/ for more information.