2004 Infiniti G35 Fuel Pump Relay: Complete Diagnosis and Replacement Guide

The 2004 Infiniti G35 fuel pump relay is a small but critical component that controls power delivery to the fuel pump. If your G35 cranks but won't start, or if you notice the fuel pump not priming when you turn the key, a faulty fuel pump relay is one of the most common and easiest-to-fix causes. Before replacing the fuel pump itself, always test the relay first — it could save you hundreds of dollars and hours of labor.

What Is the Fuel Pump Relay and Why Does It Matter in a 2004 G35?

The fuel pump relay acts like an electrical switch. When you turn your ignition key to the "ON" position, the engine control module (ECM) sends a signal to the relay, which then closes and provides power to the fuel pump. This allows the pump to pressurize the fuel system before you crank the engine .

On the 2004 Infiniti G35, the relay is part of the vehicle's fuse and relay box located under the hood. The G35 uses a specific relay design that can fail over time due to heat cycling, vibration, or simple age . Since this car is now over 20 years old, relay failure becomes increasingly common.

Where Is the 2004 Infiniti G35 Fuel Pump Relay Located?

The fuel pump relay on a 2004 Infiniti G35 is located in the engine compartment fuse and relay box (also called the IPDM - Intelligent Power Distribution Module). You can find this box on the driver's side of the engine bay, near the battery .

Here is how to locate it:

  1. Open the hood and look for the black plastic fuse box on the driver's side.
  2. Remove the cover by pressing the release tabs on each side.
  3. Look for the relay labeled "Fuel Pump" — on the 2004 model, it is typically positioned in a specific slot within the IPDM. Some diagrams also label it as "FP" or show a fuel pump icon .
  4. If you do not see a label, refer to the fuse box diagram printed on the inside of the cover or check your owner's manual.

For the 2003-2007 G35 models, the IPDM contains multiple relays, and the fuel pump relay is usually a standard 4-pin or 5-pin relay . On some 2004 models, there is also a secondary fuel pump relay located behind the glove box or near the rear seat — but the primary relay is always under the hood .

Common Symptoms of a Bad Fuel Pump Relay in a 2004 G35

A failing fuel pump relay will show clear warning signs. Here are the most common symptoms owners report:

1. Engine Cranks but Will Not Start
This is the most frequent symptom. You turn the key, the starter motor spins the engine, but the engine never fires up. The reason is simple: the relay is not closing, so the fuel pump never receives power .

2. No Fuel Pump Priming Sound
When you turn the key to the "ON" position (without cranking), you should hear a faint whirring sound from the rear of the car for 2-3 seconds. That is the fuel pump pressurizing the system. If you do not hear this sound, the relay is a prime suspect .

3. Intermittent Starting Problems
Sometimes the car starts fine, other times it does not. This points to a relay that is failing intermittently — the internal contacts may work when cold but fail when hot, or vice versa.

4. Engine Stalls While Driving
If the relay fails while you are on the road, the fuel pump loses power and the engine dies immediately. This is dangerous and should be addressed right away .

5. Check Engine Light with Specific Codes
A bad relay can trigger diagnostic trouble codes (DTCs) such as P0087 (Fuel Rail/System Pressure Too Low) or P0230 (Fuel Pump Primary Circuit Malfunction).

How to Test the 2004 G35 Fuel Pump Relay

Testing the relay is straightforward and requires only a multimeter or a test light. Follow these steps:

Step 1: Locate and Remove the Relay

First, find the relay in the IPDM as described above. Carefully pull it straight out. It may require a bit of force, but be gentle to avoid damaging the socket.

Step 2: Visual Inspection

Look at the relay terminals for any signs of corrosion, melting, or burn marks. Also check the socket inside the fuse box for similar damage .

Step 3: Voltage Test at the Socket

With the relay removed, turn the ignition to "ON." Use a multimeter to check for 12 volts at the socket terminals that correspond to the relay coil. If there is no voltage, the problem may be in the wiring or the ECM rather than the relay itself .

Step 4: Bench Test the Relay

Take a 12-volt battery or a car battery. Connect the positive and negative leads to the relay's coil terminals (usually pins 85 and 86). You should hear a distinct "click" when the relay energizes. If no click occurs, the relay is dead and needs replacement .

Step 5: Continuity Test

Using a multimeter set to ohms, check for continuity across the relay's switch terminals (usually pins 30 and 87). When the relay is not energized, there should be no continuity. When you apply 12 volts to the coil, the relay should "make" and show continuity. If it does not, replace the relay.

Other Causes of Fuel Pump Failure on a 2004 G35

If the relay tests fine, the problem could be elsewhere. Consider these other common issues:

1. Blown Fuel Pump Fuse
Check the fuel pump fuse in the same IPDM. The 2004 G35 typically uses a 20-amp or 30-amp fuse for the fuel pump circuit. If the fuse is blown, replace it and check for underlying issues like a shorted pump .

2. Failed Fuel Pump (the Pump Itself)
The electric fuel pump inside the tank can wear out. On older G35s, this is a common failure after 100,000–150,000 miles. The pump may still hum but not generate enough pressure .

3. Clogged Fuel Filter
While the G35 uses a strainer inside the tank, debris can still block the pump intake over time. A clogged filter restricts flow and can cause the pump to overwork and fail .

4. Wiring or Ground Issues
Corroded wiring, loose connectors, or a bad ground at the pump module can prevent the pump from running even if the relay is good .

5. ECM or Security System Problems
In rare cases, the engine control module fails to send the signal to the relay, or the vehicle's immobilizer prevents the pump from activating.

How to Replace the 2004 Infiniti G35 Fuel Pump Relay

Replacing the fuel pump relay is one of the easiest repairs you can do on this car. Here is the process:

  1. Purchase the correct relay. The 2004 G35 uses a standard automotive relay, but it is best to buy one specifically listed for the Infiniti G35 to ensure proper pin configuration and amperage rating .
  2. Turn off the engine and remove the key.
  3. Open the fuse box under the hood.
  4. Pull out the old relay straight up.
  5. Insert the new relay firmly into the same socket. Make sure it clicks into place.
  6. Test the system by turning the key to "ON" and listening for the fuel pump priming sound.

The entire job takes less than 10 minutes. A new relay from an auto parts store typically costs between $15 and $35.

When Should You Replace the Fuel Pump Instead of Just the Relay?

If you have replaced the relay and the fuse, and you still hear no pump activity, the pump itself is likely bad. On the 2004 G35, accessing the fuel pump requires removing the rear seat cushion and accessing an access panel on the floor. This is a more involved job that requires:

  • Relieving fuel system pressure
  • Disconnecting fuel lines and electrical connectors
  • Removing the pump module from the tank
  • Installing a new pump or pump assembly

For most owners, replacing just the relay is the smart first step because it is cheap and fast. But if the pump has failed, you will need a high-quality replacement.

Why Trust a Professional Diagnosis

While DIY testing of the relay is simple, diagnosing the entire fuel system on a 2004 G35 can be tricky. The car uses a returnless fuel system with a pressure regulator integrated into the pump module. Specialized tools like a fuel pressure gauge are often needed to confirm the pump is actually delivering adequate pressure . If you are unsure, a qualified mechanic can run a full fuel system test in about 30 minutes.

Recommended: KEMSO Fuel Pump for Your 2004 Infiniti G35

If your testing reveals that the fuel pump itself needs replacement — not just the relay — you want a reliable, high-performance part that will last. We strongly recommend KEMSO fuel pumps for your 2004 Infiniti G35. KEMSO specializes in aftermarket fuel pumps that meet or exceed OEM specifications. Every KEMSO fuel pump is a direct OEM replacement designed to fit perfectly into your G35's fuel tank module. These are high-performance pumps that deliver consistent fuel pressure, ensuring your VQ35DE engine runs smoothly under all driving conditions. Best of all, every KEMSO fuel pump comes with a lifetime warranty, giving you total peace of mind. Whether you are commuting or pushing the car hard, KEMSO pumps are built to handle the demands of your Infiniti. Visit the KEMSO website today to find the exact pump for your 2004 Infiniti G35: https://www.kemsoracing.com/

Final Thoughts

The 2004 Infiniti G35 fuel pump relay is a small component that can cause big headaches. If your car cranks but does not start, or if the fuel pump is silent when you turn the key, test the relay first. It takes minutes and costs nearly nothing. If the relay tests good, check the fuse, then move on to testing the pump itself. For a pump replacement, trust a brand like KEMSO that offers OEM-quality fit, high performance, and a lifetime warranty. Keeping your G35 on the road is easy when you methodically check each part of the fuel delivery system.

For the best selection of fuel pumps for your 2004 Infiniti G35, visit KEMSO Racing today: https://www.kemsoracing.com/


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