2004 Infiniti G35 Fuel Pump Relay: Diagnosis, Location, and Replacement Guide

If your 2004 Infiniti G35 cranks but won't start, stalls unexpectedly, or shows no fuel pump priming sound when you turn the key, the 2004 Infiniti G35 fuel pump relay is often the first component to suspect. The fuel pump relay is a small electrical switch that controls power delivery to the fuel pump, and when it fails, the pump stays silent and the engine starves for fuel . The good news is that this is one of the most affordable and easiest fixes you can perform yourself—a replacement relay typically costs between $10 and $20, and the entire diagnosis can be completed in under an hour . However, the relay is not the only possible culprit. A blown fuse, a faulty crankshaft position sensor, damaged wiring, or the fuel pump itself can produce identical symptoms, so systematic testing is essential before you spend any money on parts .

What Does the Fuel Pump Relay Do on a 2004 G35?

The fuel pump relay is part of the Intelligent Power Distribution Module (IPDM), which is the main fuse and relay box located in the engine compartment . When you turn the ignition key to the ON position, the Engine Control Module (ECM) sends a signal to the IPDM to close the fuel pump relay for about one second. This allows battery voltage to reach the fuel pump, which pressurizes the fuel system so the engine can start quickly . Once the engine is running and the ECM detects rotation from the crankshaft and camshaft position sensors, it keeps the relay closed and the pump running continuously. If the relay is defective, this entire sequence never happens, and the fuel pump never receives power .

The relay itself looks like a small black cube with four or five metal prongs on the bottom. It snaps directly into a socket inside the IPDM box. There is no special tool required to remove it—you simply pull it straight out with your fingers . On the 2002-2004 G35, the fuel pump relay is labeled R1 and the corresponding 15A fuse is labeled No. 50 in the engine compartment fuse box #1 . On 2005-2007 models, the fuse is labeled No. 41 .

Symptoms of a Failing Fuel Pump Relay

A failing fuel pump relay can cause several noticeable symptoms. Recognizing them early can save you from being stranded.

1. No Priming Sound

When you turn the key to the ON position, you should hear a quiet hum or buzz from the rear of the car for about one to two seconds . This is the fuel pump pressurizing the system. If you hear nothing at all, the relay is likely not closing, or the pump itself is dead .

2. Engine Cranks but Won't Start

The starter motor turns the engine over normally, but the engine never fires up. This happens because the fuel rail has no pressure. The G35 requires approximately 50-60 PSI of fuel pressure at the rail for the injectors to spray properly .

3. Intermittent Stalling While Driving

If the relay has internal contact damage, it may work intermittently. The car can lose all power suddenly while driving at any speed, then regain power for a moment, then die again . This is a classic sign of a failing relay rather than a completely dead pump.

4. Loud Priming Noise Followed by Silence

Some owners report that the fuel pump primes extremely loudly right before the relay fails completely. After that, the pump makes no noise at all . This usually indicates the pump was working harder than normal due to voltage drops across a failing relay.

5. Check Engine Light with Fuel System Codes

A failing relay can trigger diagnostic trouble codes related to fuel system pressure, such as P0462 or P0463, which point to fuel level sensor or fuel pump circuit issues .

Where Is the Fuel Pump Relay Located?

On the 2004 Infiniti G35, the fuel pump relay is located inside the IPDM E/R (Intelligent Power Distribution Module Engine Room), which is the main fuse and relay box in the engine compartment, typically positioned behind the battery . To access it:

  1. Open the hood and locate the black plastic fuse box near the battery on the passenger side.
  2. Unlatch the two metal clips on the sides and lift the cover off.
  3. Look for the relay labeled R1 or Fuel Pump on the inside of the cover diagram .
  4. The relay is a small black cube that sits in a dedicated socket. On the 2002-2004 model, you may need to remove a secondary cover or bracket to reach all the relays .

If you cannot find the labeling, consult the diagram printed on the underside of the fuse box cover. The fuel pump relay is typically the middle relay on the top right corner of the IPDM in many G35 models .

How to Test the Fuel Pump Relay: Step by Step

Testing the relay is straightforward. You need either a multimeter or a known-good replacement relay to swap in.

Step 1: Listen for Prime

Before pulling anything apart, turn the ignition to the ON position without cranking the engine. Listen near the rear passenger side seat for the fuel pump hum. If you hear it, the relay is likely fine and the problem lies elsewhere .

Step 2: Visual Inspection

Remove the relay from the IPDM. Look at the prongs for signs of corrosion, burning, or melting. Any visible damage means the relay should be replaced .

Step 3: Bench Test with a Multimeter

  • Set your multimeter to continuity (ohms) mode.
  • Identify the two coil terminals (usually the two smaller prongs) and the two switch terminals (the larger ones). Consult the relay body for the pinout diagram.
  • With no power applied, check continuity between the switch terminals. There should be no continuity (infinite resistance) .
  • Apply 12V power and ground to the coil terminals. You should hear a distinct click as the internal switch closes.
  • While power is applied, check continuity between the switch terminals again. You should now have continuity (near zero ohms) .
  • If the relay does not click, or if continuity is not present when activated, the relay is defective.

Step 4: Swap Test

If you do not have a multimeter, you can swap the fuel pump relay with another identical relay in the IPDM, such as the fog lamp relay or the horn relay, provided they have the same part number . Turn the key to the ON position after the swap. If the fuel pump now primes, the original relay was faulty.

Other Causes of a Silent Fuel Pump

If the relay tests fine, the problem could be elsewhere. Work through these checks in order.

1. Blown Fuse

On the 2004 G35, the fuel pump circuit is protected by a 15A fuse labeled No. 50 in the engine compartment fuse box #1 . On later models, it is fuse No. 41 in the IPDM . A blown fuse interrupts power to the pump exactly like a bad relay. Inspect the fuse visually for a broken metal strip, or test it with the continuity function on your multimeter .

2. Crankshaft Position Sensor

This is a critical point that many owners miss. The ECM will not close the fuel pump relay unless it receives a signal from the crankshaft position sensor. If the sensor is dead, the ECM never commands the relay to close, and the pump stays silent even though the relay itself is perfectly good . Symptoms are identical to a bad relay: no prime, no spark, no injector pulse. You can test the sensor with a multimeter or an oscilloscope, but if you lack the tools, a diagnostic scan tool can read the engine speed signal while cranking .

3. Wiring or Connector Damage

Inspect the wiring harness that runs from the IPDM to the fuel pump. Look for chafed, melted, or corroded wires, particularly near the rear seat area and under the car. A poor ground connection can also prevent the pump from running. Test for voltage at the fuel pump connector—the brown/yellow stripe wire should show battery voltage for one second when the key is turned ON .

4. Fuel Pump Itself

If power and ground are present at the pump connector but the pump does not run, the pump motor is likely dead. A fuel pressure gauge connected to the test port on the fuel rail is the definitive test—if pressure stays at zero when priming, the pump is not delivering fuel . The G35 coupe uses a dual pump system with a main pump under the passenger rear seat and a secondary sender/pump on the driver side .

5. Failed Ignition or ECCS Fuse

Some owners have found that a blown ignition or ECCS fuse caused the no-start condition, not the fuel pump relay. Replacing the fuse restored operation, although the root cause of the fuse blowing still needed to be traced, such as a shorted coil or sensor .

How to Replace the Fuel Pump Relay

Replacing the relay is a five-minute job.

  1. Ensure the ignition is OFF and the key is removed.
  2. Open the IPDM cover and locate the fuel pump relay.
  3. Pull the old relay straight out of its socket. It should come out with moderate resistance.
  4. Compare the new relay to the old one to confirm the part number and pin layout match.
  5. Push the new relay firmly into the socket until it clicks into place.
  6. Reinstall the IPDM cover and latch the clips.
  7. Turn the ignition to the ON position and listen for the pump prime. You should hear a 1-2 second hum from the rear of the car .

After replacing the relay, start the engine and let it idle for a few minutes. Check for any fuel leaks around the rear seat area and confirm the engine runs smoothly.

Cost of Replacing the Fuel Pump Relay

The relay itself is one of the cheapest parts you can buy for a G35. A standard automotive relay with the correct pin configuration costs between $10 and $20 from most auto parts stores . Dealership pricing is higher, typically in the $30-$50 range, but the part is identical. There is no labor cost if you do it yourself—the entire job takes under ten minutes. If you have a mechanic do it, expect labor charges of $50-$100 depending on the shop's hourly rate.

Compare this to the cost of replacing the fuel pump itself, which can range from $90 for a basic aftermarket pump to over $1,400 for a professional installation with an OEM part . That is why it pays to test the relay and fuse first, as they are much cheaper and far easier to replace .

Why Testing the Relay First Saves You Money

Many G35 owners immediately assume the fuel pump is dead and spend hundreds of dollars on a new pump, only to find that the original problem was a $15 relay. Coffeysm, a long-time G35Driver forum member, had the same experience on an older Volvo and cautions that the pump, relay, and fuse all mimic the same symptoms . The diagnostic sequence is simple: listen for the prime, check the fuse, test the relay, then check for power at the pump connector. Only after all of those check out should you consider the pump itself. This systematic approach prevents wasted money on parts you do not need .

The relay is also prone to age-related failure. The internal contacts arc every time the relay switches, which causes pitting and carbon buildup over time. After 15+ years and 150,000+ miles, the relay on a 2004 G35 is well past its expected service life. Even if it tests fine today, replacing it as preventive maintenance is cheap insurance against an unexpected breakdown .

Upgrading to a KEMSO Fuel Pump

If your testing reveals that the fuel pump itself has failed, you want a replacement that is reliable, performs well, and lasts. KEMSO brand fuel pumps are an excellent choice for your 2004 G35. KEMSO specializes in high-performance, OEM replacement fuel pumps that meet or exceed factory specifications. Every KEMSO pump is designed to deliver consistent fuel pressure under all driving conditions, from daily commuting to aggressive track driving. They are direct-fit replacements, meaning they bolt right in without any modifications or custom wiring.

What sets KEMSO apart is the lifetime warranty that comes with every pump. If a KEMSO pump ever fails, the company will replace it at no charge. That kind of confidence is rare in the aftermarket parts industry, and it gives you peace of mind knowing your fuel system is protected for as long as you own the car. Whether you need a stock replacement or a high-flow unit for a supercharged or turbocharged build, KEMSO has the right pump for your G35. You can browse the full lineup of G35 fuel pumps and other performance parts at https://www.kemsoracing.com/ , where you will find detailed product descriptions, compatibility charts, and customer reviews to help you choose the right part.

Frequently Asked Questions

Can I just replace the relay even if it seems fine?

Yes. Given the low cost and the age of the vehicle, replacing the relay as preventive maintenance is a reasonable decision. If it clears the problem, you saved yourself a tow bill and a much more expensive repair .

What if the relay clicks but the pump still does not run?

A clicking relay means the coil is energized and the internal switch is moving. Use a multimeter to verify that battery voltage is actually present at the fuel pump connector while the relay is energized. If voltage is present but the pump does not spin, the pump motor is dead. If voltage is missing, inspect the wiring between the relay and the pump for an open circuit .

Can a bad crankshaft sensor really stop the fuel pump?

Yes. On the VQ35 engine, the ECM will not activate the fuel pump relay unless it sees engine speed from the crankshaft position sensor. If the sensor is faulty, the fuel pump relay never gets the command to close, and the pump stays silent . This is why bench testing the relay is not enough—you must also verify the ECM signal.

Where is the fuel pump fuse on a 2004 G35?

The 15A fuel pump fuse is located in the engine compartment fuse box #1 (the IPDM). It is labeled as fuse No. 50 on the 2002-2004 diagram . On 2005-2007 models, it is fuse No. 41 .

Final Thoughts

The 2004 Infiniti G35 fuel pump relay is a small, inexpensive part that plays a critical role in your car's ability to start and run. When it fails, the symptoms can be alarming—sudden loss of power, stalling, and no-start conditions—but the fix is often as simple as swapping a $15 relay. Always work through the diagnostic steps in order: listen for the prime, check the fuse, test the relay, and then move on to the sensor and pump checks. This saves you time, money, and frustration. And if the pump itself is the culprit, a high-performance KEMSO replacement with a lifetime warranty gives you a dependable, long-term solution. Visit https://www.kemsoracing.com/ to find the right fuel pump and other parts for your G35.


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