Acura TL Fuel Pump Relay Location: Find, Test, and Replace It Yourself

The fuel pump relay in most Acura TL models (specifically the third generation, 2004-2008) is located in the under-hood fuse box, typically positioned near the battery. It is often found in slot #7 within that fuse box. Locating and understanding this small but critical component is essential if you're experiencing starting problems or suspect fuel delivery issues with your Acura TL. Knowing precisely where it is and how to check it can save you significant time and money on diagnostics and repairs.

Understanding the Fuel Pump Relay's Role

Before diving into its location, it's crucial to grasp what the fuel pump relay does and why it matters. Think of it as the gatekeeper for your fuel pump's electrical power. When you turn the ignition key to the "ON" position (or press the start button without engaging the starter), the Engine Control Module (ECM) sends a signal to activate the fuel pump relay. This relay then closes an internal switch, allowing battery voltage to flow through to the fuel pump itself. The pump runs for a few seconds to pressurize the fuel system, readying the engine for startup. When you crank the engine, the ECM keeps the relay activated, ensuring continuous fuel flow. If this relay fails, the fuel pump doesn't receive power, meaning no fuel pressure, and consequently, the engine won't start or run.

Precise Location: Under-Hood Fuse Box

For the vast majority of Acura TL owners, specifically those with the popular third-generation models (2004-2008), the primary fuse box containing the fuel pump relay is located under the hood. Here's how to find it:

  1. Open the Hood: Securely prop open the hood of your Acura TL.
  2. Locate the Fuse Box: Look towards the rear of the engine compartment, on the driver's side (left side for North American vehicles). You'll see a rectangular black plastic box. This is the main under-hood fuse and relay box. It's usually situated near the battery and the brake fluid reservoir.
  3. Open the Fuse Box Lid: The lid is secured by clips. Press the clips inward or pull them outward (depending on the design) and lift the lid off. Set it aside safely.
  4. Identify the Relay: Once the lid is off, look at the underside of the lid. There should be a detailed diagram or chart listing all the fuses and relays inside the box and their designated positions (slots). Find the slot labeled for the "Fuel Pump" relay. On most 2004-2008 Acura TLs, this relay is located in Slot #7. It might also be labeled as "PGM-FI Main Relay 2" or similar in some diagrams, but its function is primarily for the fuel pump.
  5. Visual Confirmation: Look inside the fuse box at slot #7. You should see a small, cube-shaped component, usually black, plugged into the socket. This is a standard automotive relay. Compare it to the diagram on the lid to double-check.

Important Considerations Regarding Location

  • Model Year Variations: While Slot #7 in the under-hood box is standard for 2004-2008 TLs, always verify using the diagram on your specific fuse box lid. Acura occasionally makes minor changes. For other generations (like the 1999-2003 second-gen), the primary fuel pump relay location might differ slightly or be shared with another function. Consult your owner's manual if unsure.
  • Secondary Locations: While the under-hood box is the primary location, some vehicles might have relays related to the fuel system elsewhere. However, for the core fuel pump power relay, the under-hood box is the place to look first on a 3G TL.
  • Relay Appearance: The fuel pump relay looks identical to many other relays in the box (like the radiator fan relay or A/C compressor relay). Relying solely on its appearance isn't enough; you must use the diagram on the lid to identify it correctly by its slot position and label.

How to Identify the Fuel Pump Relay

Since relays often look alike, positive identification is key:

  1. Lid Diagram: This is your most reliable source. Find "Fuel Pump" or "PGM-FI Main Relay 2" on the chart and note the slot number (e.g., #7).
  2. Owner's Manual: Your Acura TL's owner's manual will have a section dedicated to fuse and relay locations, complete with diagrams. Refer to this if the lid diagram is missing or unclear.
  3. Swap Test (Use with Caution): If you suspect the relay is faulty and there's an identical relay in the box controlling a non-critical system (like the horn or rear defogger), you can carefully swap them. If the horn stops working but the car starts, you've identified the faulty relay. Important: Only swap with relays rated for the same amperage (check the lid diagram or relay body). Never swap with relays for critical systems like the ECU or ignition.
  4. Relay Pinout: If you have a multimeter and wiring diagram knowledge, you can check for voltage at specific pins when the ignition is turned on. However, this is more advanced.

Symptoms of a Failing Fuel Pump Relay

A faulty fuel pump relay is a common cause of no-start conditions. Be aware of these signs:

  1. Engine Cranks But Won't Start: This is the classic symptom. The starter motor turns the engine over normally, but the engine doesn't fire up because no fuel is being delivered.
  2. No Fuel Pump Prime Sound: When you turn the ignition key to "ON" (without cranking), you should hear a faint whirring or humming sound from the rear of the car (where the fuel tank is) for about 2-3 seconds. This is the fuel pump priming the system. If you hear no sound at all during this stage, a faulty relay (or fuse, or pump) is a prime suspect.
  3. Intermittent Starting Problems: The relay might work sometimes and fail other times. You might experience a no-start condition randomly, which later resolves itself, only to return later. This can be caused by internal corrosion or a failing solder joint within the relay.
  4. Engine Stalls While Driving: In rare cases, if the relay fails while the engine is running, it can cause the engine to stall abruptly as fuel delivery ceases. It might restart after cooling down if the relay is heat-sensitive.

How to Test the Acura TL Fuel Pump Relay

Testing the relay is a straightforward process that requires minimal tools:

What You'll Need:

  • Basic set of screwdrivers (for fuse box lid clips, usually not needed for the relay itself)
  • Multimeter (Digital Multimeter - DMM - is preferred)
  • A helper (optional but helpful)

Steps:

  1. Locate and Remove: Identify the fuel pump relay using the lid diagram and remove it by gently pulling it straight up out of its socket. It might require a slight rocking motion if it's snug.
  2. Visual Inspection: Examine the relay. Look for signs of burning, melting, corrosion on the pins, or cracks in the plastic casing. Any obvious physical damage means the relay needs replacement.
  3. Shake Test: Gently shake the relay near your ear. If you hear anything rattling inside (like loose components), the relay is likely faulty.
  4. Multimeter Resistance Test (Coil Side):
    • Set your multimeter to measure resistance (Ohms, Ω).
    • Look at the relay base. The pins are usually numbered or labeled on the bottom or side. Refer to a generic 4-pin or 5-pin relay diagram online if yours isn't labeled. Typically, two pins belong to the relay's control coil.
    • Touch the multimeter probes to these two coil pins. You should read a resistance value, usually between 50 and 150 ohms. A reading of infinite resistance (OL or overload) means the coil is open and the relay is dead. A reading of zero ohms indicates a shorted coil.
  5. Multimeter Continuity Test (Switch Side - Relay Out):
    • Set your multimeter to continuity (the setting that beeps) or the lowest Ohms setting.
    • Identify the two pins that form the switch contacts (usually the high-current path). On a standard 4-pin relay, these are often pins 30 and 87.
    • Touch the probes to these two pins. With the relay removed and unpowered, there should be no continuity (no beep, high resistance reading). This means the switch is open when the relay is off.
  6. Bench Test (Activating the Relay):
    • You need a way to apply 12 volts to the relay's coil pins. A small 12V battery (like a motorcycle battery) or even a 9V battery might work for testing continuity (though 9V may not reliably pull the switch closed on some relays). The safest and most reliable method is to use jumper wires connected to your car's battery terminals (BE CAREFUL OF SHORTS!).
    • Connect the positive (+) jumper wire from the battery positive terminal to one of the relay's coil pins.
    • Connect the negative (-) jumper wire from the battery negative terminal to the other coil pin. You should hear and feel a distinct "click" as the relay's internal switch closes.
  7. Multimeter Continuity Test (Switch Side - Relay Activated):
    • While keeping the 12V power applied to the coil pins (your helper can hold the wires if needed), touch the multimeter probes to the switch contact pins (e.g., 30 and 87).
    • You should now have continuity (a beep or very low resistance reading near 0 ohms). This confirms the switch inside the relay is closing properly when the coil is energized.
  8. Socket Voltage Test (Advanced):
    • Reinsert the relay into its socket.
    • Set the multimeter to measure DC Voltage (20V range).
    • Turn the ignition key to the "ON" position (do not crank).
    • Carefully back-probe the socket terminals corresponding to the relay's coil pins (refer to diagram). You should see battery voltage (around 12V) on one coil pin. The other coil pin should be the ground path controlled by the ECM; it might show 0V or a lower voltage until the ECM activates it. When the ECM activates the relay (during the prime cycle), you should see the ground pin go to near 0V relative to battery negative.
    • Back-probe the socket terminal for pin 87 (the output to the fuel pump). During the prime cycle (ignition ON), you should see battery voltage here if the relay is working.

Replacing the Acura TL Fuel Pump Relay

If testing confirms the relay is faulty, replacement is simple:

  1. Purchase the Correct Relay: Take the old relay to an auto parts store or consult your owner's manual/dealership for the exact part number. Common Acura/Honda relay part numbers include 39400-S6A-A01, 39400-S6A-A02, 39400-S6A-A11, or 39400-SMA-A01. Ensure the new relay matches the old one physically and in pin configuration. Generic relays (like a standard Bosch 0332019150) are often direct replacements and less expensive than OEM.
  2. Turn Off Ignition: Ensure the ignition is completely off.
  3. Remove Old Relay: Locate the relay in the under-hood fuse box and pull it straight out.
  4. Install New Relay: Align the new relay correctly with the socket (pins must match the holes) and push it firmly down until it seats completely.
  5. Test: Turn the ignition key to "ON" and listen for the fuel pump prime sound (2-3 seconds). If you hear it, attempt to start the engine. If the engine starts and runs normally, the repair was successful.

Cost Considerations

Fuel pump relays are inexpensive components:

  • OEM Acura/Honda Relay: Typically 40.
  • Aftermarket Relay: Often 20.
    Replacement takes only a few minutes, making this one of the most cost-effective repairs if it solves your no-start issue.

Safety First

  • Always disconnect the negative battery terminal before working on electrical components if you need to remove fuses or relays, especially if testing involves probing sockets. This prevents accidental shorts.
  • Be mindful of moving engine parts (fans, belts) when the hood is open and the engine is running.
  • Fuel systems are under pressure. While testing the relay doesn't involve direct fuel contact, remember that a malfunctioning relay could be a symptom of other issues. If you smell fuel strongly, stop immediately and investigate for leaks before proceeding.

When the Relay Isn't the Problem

If you've replaced the relay and the fuel pump still doesn't prime or the car won't start, the problem lies elsewhere. Other common culprits include:

  1. Fuel Pump Fuse: Check the fuse associated with the fuel pump circuit. It's usually in the same under-hood fuse box. Use the lid diagram to find it and visually inspect or test it with a multimeter for continuity.
  2. Faulty Fuel Pump: The pump itself may have failed. Testing the pump requires checking for power and ground at the pump connector (usually near the fuel tank) or listening for its operation directly.
  3. Wiring Issues: Corrosion, breaks, or shorts in the wiring harness between the relay, fuse, ECM, and fuel pump can cause failure.
  4. Ignition Switch Problem: A faulty ignition switch might not be sending the correct signal to the ECM to activate the relay.
  5. ECM Failure: While less common, a problem with the Engine Control Module could prevent it from sending the activation signal to the relay.

Conclusion

Knowing the Acura TL fuel pump relay location – specifically in slot #7 of the under-hood fuse box for 2004-2008 models – empowers you to quickly diagnose and potentially resolve a common cause of no-start conditions. Identifying it using the fuse box lid diagram, performing simple tests with a multimeter, and replacing it if faulty are well within the scope of a DIY enthusiast. Always prioritize safety, double-check the location against your specific vehicle's diagram, and systematically test components before replacing parts. Addressing a faulty fuel pump relay promptly can get your Acura TL back on the road reliably and inexpensively. If replacing the relay doesn't solve the problem, further investigation into the fuel pump, fuses, and related wiring will be necessary.

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