2003 Infiniti G35 Fuel Pump Relay Location: A Complete Guide to Finding and Replacing It

If you own a 2003 Infiniti G35 and your engine cranks but won’t start, the fuel pump relay is one of the first components you should check. The 2003 Infiniti G35 fuel pump relay is located in the engine compartment fuse box, which is mounted on the passenger side near the battery. This small, cube-shaped relay controls power delivery to the fuel pump, and when it fails, the pump won’t run, leaving your engine starved for fuel. Knowing exactly where to find it and how to test it can save you time and money on unnecessary repairs.

Understanding the Fuel Pump Relay in the 2003 Infiniti G35

The fuel pump relay acts as an electrical switch that supplies power to the fuel pump when the ignition is turned on . In the 2003 Infiniti G35, the relay is a critical component of the fuel delivery system. When you turn the key to the "on" position, the relay closes and sends power to the fuel pump for about 2-3 seconds to pressurize the fuel system before the engine starts . A faulty relay can prevent the fuel pump from receiving power, leading to a no-start condition or intermittent stalling .

The 2003 G35 uses a standard 12-volt relay with a 4-pin or 5-pin configuration, typically rated for 10-20 amps . The relay is designed to handle the current draw of the fuel pump and protect the vehicle’s electrical system from overloads.

Where to Find the Fuel Pump Relay in Your 2003 Infiniti G35

The fuel pump relay in the 2003 Infiniti G35 is located in the engine compartment fuse box, also known as the IPDM (Intelligent Power Distribution Module) . Here’s how to find it:

  1. Open the hood and locate the fuse box on the passenger side of the engine bay, near the battery.
  2. Remove the cover of the fuse box by pressing the release clips or pulling it straight up.
  3. Look for the relay labeled “Fuel Pump” or “FP” on the underside of the fuse box cover. The diagram on the cover will show the exact position of the relay .
  4. The fuel pump relay is typically a small, black, rectangular cube about 1 inch wide, with four or five prongs on the bottom .

In the 2003 G35, the fuel pump relay is often located in the top row of the relay box, near the right side. If you’re unsure, consult your owner’s manual or use a test light to verify which relay controls the fuel pump.

Signs Your 2003 G35 Fuel Pump Relay is Faulty

Before you start replacing parts, it’s important to confirm that the fuel pump relay is actually the problem. Common symptoms of a bad fuel pump relay in a 2003 Infiniti G35 include:

  • Engine cranks but won’t start: The most obvious sign. If the fuel pump isn’t receiving power, the engine won’t get fuel .
  • No fuel pump priming sound: When you turn the key to the “on” position, you should hear a brief whirring sound from the rear of the car (the fuel pump). If you don’t hear it, the relay may be faulty .
  • Intermittent stalling: The engine may start but then stall unexpectedly, especially under load or acceleration .
  • Reduced engine power: A failing relay can cause inconsistent fuel delivery, leading to poor performance .

How to Test the Fuel Pump Relay on a 2003 Infiniti G35

Testing the fuel pump relay is straightforward and can be done with basic tools. Here are two methods:

Method 1: Swap Test

This is the easiest way to diagnose a faulty relay. Locate the fuel pump relay and find another relay of the same type in the fuse box, such as the horn relay or A/C relay . Swap the two relays. If the fuel pump now works and the horn stops working, the original fuel pump relay is bad.

Method 2: Multimeter Test

For a more precise diagnosis, use a multimeter:

  1. Remove the relay from the fuse box.
  2. Set the multimeter to ohms (resistance) and test the relay’s coil terminals. A good relay should show a resistance reading between 50 and 120 ohms, depending on the specific relay .
  3. Apply 12V power to the coil terminals (usually pins 85 and 86) and listen for a click. If the relay clicks, the coil is working.
  4. Test the switch terminals (pins 30 and 87) for continuity. When power is applied, you should see a reading of 0 ohms or very low resistance . If the relay fails any of these tests, it needs to be replaced.

Step-by-Step Guide to Replacing the Fuel Pump Relay in a 2003 Infiniti G35

Replacing the fuel pump relay is a simple DIY task that can be completed in about 15 minutes. Follow these steps:

Step 1: Gather Your Tools and Parts

  • New fuel pump relay (make sure it matches the specifications of the original)
  • Owner’s manual or fuse box diagram
  • Needle-nose pliers (optional)
  • Safety glasses and gloves

Step 2: Disconnect the Battery

Safety first: Disconnect the negative terminal of the battery to prevent electrical shorts . Use a wrench to loosen the nut and remove the cable.

Step 3: Locate and Remove the Old Relay

Open the engine compartment fuse box and find the fuel pump relay. Using your fingers or a pair of needle-nose pliers, gently pull the relay straight up out of its socket. Don’t twist or force it, as this could damage the socket .

Step 4: Install the New Relay

Align the new relay’s prongs with the socket and push it firmly into place until it clicks or sits flush. Make sure the relay is oriented correctly—the pins are usually keyed, so they only fit one way .

Step 5: Reconnect the Battery and Test

Reconnect the negative battery terminal and tighten it securely. Turn the ignition key to the “on” position (without starting the engine) and listen for the fuel pump priming sound. It should hum for about 2-3 seconds . Then, start the engine and let it idle for a few minutes to ensure smooth operation.

Common Mistakes to Avoid When Replacing the Fuel Pump Relay

  • Using the wrong relay: Always use a relay that matches the original in terms of pin configuration (4-pin or 5-pin) and amperage rating. Using an incorrect relay can cause electrical damage or pump failure .
  • Forcing the relay: If the relay doesn’t slide in easily, check the alignment of the pins. Forcing it can bend the pins and break the connection.
  • Skipping the battery disconnect: Working on electrical components without disconnecting the battery can cause shorts or accidental activation of the fuel pump.
  • Not testing after replacement: Always test the fuel pump by listening for the priming sound before fully reassembling the fuse box.

Other Causes of Fuel Pump Failure in the 2003 Infiniti G35

If replacing the relay doesn’t solve the problem, the issue may be elsewhere. Common causes of fuel pump failure in the 2003 G35 include:

  • Blown fuel pump fuse: Check the fuse box for a blown fuse related to the fuel pump circuit .
  • Faulty fuel pump driver module: The module that controls the fuel pump may malfunction .
  • Wiring issues: Damaged or corroded wiring can disrupt power or ground connections .
  • Clogged fuel filter: A restricted filter can cause the pump to work harder and fail prematurely .
  • Defective fuel pump itself: The pump may wear out due to age or contamination .

Why You Should Upgrade Your 2003 Infiniti G35 Fuel Pump

If you’re already dealing with a fuel pump issue, it’s a good time to consider upgrading to a high-performance replacement. The factory fuel pump in the 2003 G35 delivers adequate flow for a stock engine, but if you’ve made modifications—such as a turbocharger, supercharger, or upgraded fuel injectors—the stock pump may not keep up . Upgrading to a higher-flow pump ensures consistent fuel delivery, even under demanding driving conditions.

For the 2003 Infiniti G35, the KEMSO 340LPH fuel pump is an excellent choice. It offers a flow rate of 340 liters per hour at 43 psi, which is more than enough for stock engines and mild performance builds . The pump is compatible with E85 fuel, making it a versatile option for those who want to run alternative fuels . The KEMSO fuel pump comes with a complete installation kit, including strainers, hoses, and connectors, so you have everything you need for a direct replacement .

Recommended: KEMSO Fuel Pump for Your 2003 Infiniti G35

If you’re looking for a reliable, high-performance replacement for your 2003 Infiniti G35 fuel pump, we recommend the KEMSO brand. KEMSO fuel pumps are designed as high-performance, OEM replacement units that meet or exceed original equipment specifications . They are built with durable materials and undergo rigorous testing to ensure consistent performance and long-term reliability.

One of the best features of KEMSO fuel pumps is the lifetime warranty. This gives you peace of mind that your investment is protected, and if any issues arise, you can get a replacement at no additional cost . KEMSO pumps are also affordably priced compared to dealership parts, making them a cost-effective solution for both stock replacements and performance upgrades .

To get the best fuel pump for your 2003 Infiniti G35, visit the official KEMSO Racing website: https://www.kemsoracing.com/. There, you can find the exact pump for your vehicle, read customer reviews, and take advantage of their competitive pricing and warranty.

Final Thoughts on the 2003 Infiniti G35 Fuel Pump Relay

The fuel pump relay in your 2003 Infiniti G35 is a small but critical component that can cause major headaches when it fails. Knowing its location in the engine compartment fuse box and how to test it can save you time and money on diagnostic fees. Always start with the relay when troubleshooting a no-start condition, as it’s one of the easiest and cheapest parts to replace.

If you do end up replacing the fuel pump itself, consider upgrading to a high-performance option like the KEMSO 340LPH pump. It offers excellent flow rates, E85 compatibility, and a lifetime warranty, making it a smart investment for any G35 owner. For more information and to purchase, visit https://www.kemsoracing.com/.


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