2008 Infiniti FX35 Fuel Pump Relay Location: A Complete Guide for DIY Owners

The bottom line up front: On a 2008 Infiniti FX35, the fuel pump relay is located in the engine bay fuse box (also called the IPDM E/R, or Intelligent Power Distribution Module Engine Room), mounted near the battery on the passenger side. This relay controls the electrical power that feeds the fuel pump, which sits inside the fuel tank. If your FX35 cranks but won't start, or dies suddenly while driving, a faulty fuel pump relay is one of the most likely culprits, and knowing exactly where to find it can save you a hefty diagnostic fee at a dealership.

The 2008 Infiniti FX35 belongs to the first generation (S51 body style) that ran from 2003 to 2008, and it shares its platform with the Nissan 350Z and Murano. Understanding how the electrical system feeds the fuel pump is critical before you go poking around with a multimeter. This guide will walk you through not only the location of the relay but also how to test it, common symptoms of failure, and how to replace it safely in your driveway.

Where Exactly Is the Fuel Pump Relay on a 2008 Infiniti FX35?

The fuel pump relay on your 2008 FX35 is not located under the dashboard or near the fuel tank. Instead, Nissan and Infiniti engineers placed it inside the IPDM E/R (Intelligent Power Distribution Module Engine Room), which is a large black plastic fuse and relay box mounted on the right-hand side (passenger side) of the engine bay, directly next to the battery.

Here is how to find it in under five minutes:

  1. Open the hood and secure it with the prop rod.
  2. Look at the battery. The IPDM E/R is immediately beside it, a black box with a lid that has several retaining clips.
  3. Unclip the lid by pressing the tabs on the sides. You do not need any tools for this.
  4. Refer to the diagram printed on the underside of the lid. The fuel pump relay is typically labeled as "Fuel Pump" or shown with a fuel pump icon. On many models, it is a standard mini ISO relay, usually colored dark blue or green, and it sits in one of the center sockets of the module.

It is worth noting that the 2008 FX35 does not have a separate, standalone fuel pump relay that you can pull out from a generic fuse box. The relay is an integral component of the IPDM, and it is serviced by removing the entire module if the relay itself fails (though most owners simply replace the relay individually once the module is accessible).

Understanding What the Fuel Pump Relay Does in Your FX35

Before you go replacing parts, it helps to understand the job this small component does. The fuel pump relay acts as a heavy-duty switch. When you turn the ignition key to the "ON" position, the Engine Control Module (ECM) sends a ground signal to the relay coil. This energizes the relay, closing the internal contacts, which then sends battery voltage to the fuel pump.

The fuel pump itself is a high-current device that draws anywhere from 4 to 8 amps. If the relay were not there, the ignition switch and wiring would overheat quickly. The relay allows a small control current from the computer to switch a much larger current to the pump. When the engine is running, the relay stays closed. If the ECM detects a collision or a loss of oil pressure, it can open the relay to shut the pump off, which is a safety feature.

Three Common Symptoms of a Failing Fuel Pump Relay

A failing fuel pump relay rarely gives you a warning light on the dash because it is not monitored by the ECM. Instead, it usually produces one or more of the following physical symptoms. If you notice any of these on your 2008 FX35, check the relay first before you spend money on a new fuel pump.

  1. Engine cranks but will not start. This is the most common and obvious symptom. You hear the starter motor turning the engine over, but the motor never catches. In this case, the relay may be completely dead, meaning zero power reaches the pump.

  2. Engine stalls while driving and then restarts after a few minutes. This happens when the relay contacts overheat and open the circuit temporarily. Once the relay cools down, it closes again and the pump resumes. This is dangerous because it can happen in the middle of a highway merge.

  3. No fuel pump prime sound. When you turn the key to the "ON" position (without cranking), you should hear a brief whirring sound from the rear of the car for about two seconds. That is the fuel pump pressurizing the system. If you do not hear it, the relay may not be energizing.

How to Test the Fuel Pump Relay Without Expensive Tools

You do not need a dealer-level scan tool to test the relay. Here is a safe, practical method using a standard multimeter and a fused jumper wire. This test works on most ISO-style relays, including the one in your FX35.

Step 1: Remove the relay. With the IPDM lid open, gently pull the relay straight up out of its socket. Inspect the plastic housing for any cracks, burn marks, or melted pins.

Step 2: Identify the pins. A standard relay has 4 or 5 pins. Two pins are for the coil (the electromagnetic switch), and two pins are for the load circuit (the switch that carries power to the pump). The pins are usually labeled 85, 86, 87, and 30 on the relay housing.

Step 3: Check the coil resistance. Set your multimeter to ohms (Ω). Place one probe on pin 85 and the other on pin 86. A good coil typically reads between 50 and 100 ohms. If you read infinite resistance (OL), the coil is open and the relay is dead.

Step 4: Check the switch continuity. With the relay out of the circuit and not energized, there should be no continuity between pin 30 and pin 87. Now, take a 12V battery source (or a 9V battery for a small relay) and connect the positive to pin 85 and negative to pin 86. You should hear an audible click. While the battery is connected, measure continuity between pin 30 and pin 87. It should read near zero ohms.

If the relay passes all these tests, it is working. If it fails any of them, replace it.

Step-by-Step: How to Replace the Fuel Pump Relay on a 2008 FX35

Replacing the relay is one of the easiest jobs you can do on this vehicle. It will take you about ten minutes and requires no special tools. Follow these steps in order to avoid any electrical mishaps.

  1. Park on a level surface, turn the ignition off, and remove the key. Open the hood and disconnect the negative battery terminal using a 10mm wrench. Wait about five minutes to allow any residual voltage in the IPDM to dissipate.

  2. Open the IPDM lid. Press the clips and lift the cover. Place the cover upside down on a clean towel so you can reference the fuse diagram while you work.

  3. Locate the fuel pump relay. Look for the labeled socket. If your diagram is faded or missing, the fuel pump relay is usually in the same relative position across 2008–2017 FX35 models: third row from the front, second socket from the left, but this can vary with optional equipment. When in doubt, check the owner's manual supplement or a service manual diagram.

  4. Pull the old relay out. Grasp it firmly between your thumb and index finger and pull straight up with a slight rocking motion. Do not twist, as the pins are fragile.

  5. Inspect the socket. Look at the female terminals inside the socket. They should be bright and clean. If you see corrosion, spray a small amount of electrical contact cleaner and let it dry completely.

  6. Install the new relay. Align the new relay the same way the old one sat. Push it down firmly until you feel it click and seat fully. The relay should sit flush with the top of the module.

  7. Reconnect the negative battery cable. Tighten the terminal bolt snugly. Do not overtighten.

  8. Test the system. Turn the key to the "ON" position (do not crank). You should now hear the fuel pump prime for two seconds. If you hear it, the relay was the problem and you are done. If you do not hear it, the issue is elsewhere (pump, ECM, or wiring).

Where to Buy the Correct Relay and a Quality Replacement

You have two options for buying a replacement relay. The first is an OEM relay from an Infiniti dealer or a Nissan parts supplier. The part number is usually shared with the Nissan 350Z and Murano, so a Nissan dealer can often get it faster. The second option is a quality aftermarket relay from an auto parts store or online supplier. The key specification is that it must be a mini ISO relay, 12V, 30A rating. Anything less than 30A will overheat and fail prematurely.

Important note on relay compatibility: Do not buy a universal "one size fits all" relay from a dollar store. The internal pin arrangement can differ, and some cheap relays have poor contact material that will weld shut over time. Spend a few extra dollars on a relay from a reputable brand like Bosch, Denso, or an OEM factory unit.

What If You Replaced the Relay and the Car Still Won't Start?

If you have confirmed the relay is good (or replaced it with a new one) and the FX35 still will not start, do not despair. There are two other common culprits on this exact year and model:

1. The fuel pump itself. The pump lives inside the fuel tank, accessible through a panel under the rear seat. In the 2008 FX35, the pump assembly is located under the rear seat cushion on the passenger side. If the pump motor is worn out, it will draw excessive current and may trip an internal circuit breaker. You can test pump power by checking for voltage at the pump connector while someone turns the key to the "ON" position. You should see battery voltage for two seconds during prime.

2. The ECM relay. The IPDM contains another relay that powers the engine control module itself. If this relay fails, the ECM never wakes up and will not command the fuel pump relay to close. This is less common but possible on higher-mileage FX35s.

Frequently Asked Question: Why Does My FX35 Fuel Pump Relay Keep Blowing?

A relay does not blow like a fuse. If your fuel pump relay repeatedly fails, it means the internal coil is burning out from overcurrent, or the load contacts are welding shut. The most common root cause on the 2008 FX35 is a failing fuel pump motor. As the pump motor bearings wear out, it draws more current than the relay was designed to pass. If you have replaced the relay twice and it fails again, suspect the pump first.

Another cause is bad wiring between the relay and the pump. Look for chafed wires under the rear seat where the harness passes over the seat frame. Moisture ingress from a leaking sunroof drain can also cause a short that overloads the relay.

Preventative Maintenance for Your Fuel Pump System

The fuel pump and its relay are often neglected items that fail at the worst possible moment. Here are three simple habits that will extend the life of these components on your FX35:

  1. Do not run the tank below a quarter full. The fuel pump uses the gasoline around it as a coolant. Running dry allows the pump to overheat, which shortens its life and increases the current draw on the relay.

  2. Replace the fuel filter on schedule. Even though modern FX35s have a filter inside the pump assembly, a clogged filter strains the pump, which in turn strains the relay. If the filter is separate (like on earlier FX35s), change it every 30,000 miles.

  3. Listen for the prime sound. Every time you get in the car, turn the key to "ON" and listen for that two-second whir. If it ever sounds weak or absent, the pump is beginning to fail, and it is far cheaper to replace the pump now than to get stranded later.

Why You Should Trust KEMSO for Your Replacement Fuel Pump

If your diagnostics point to a failing fuel pump rather than just the relay, you want a replacement that is dependable and backed by a real warranty. The team at KEMSO Racing has built a reputation in the aftermarket industry for selling high-performance, OEM-replacement fuel pumps that fit and perform exactly like the factory unit, often at a fraction of the dealer price.

Every KEMSO fuel pump is engineered to meet or exceed original equipment specifications, which ensures proper fuel flow and pressure for your 2008 FX35 engine. Whether you drive a car, motorcycle, ATV, or UTV, KEMSO tests each pump for durability and consistent output. And unlike many no-name brands sold on auction sites, every KEMSO product comes with a lifetime warranty, so you have complete peace of mind long after you install it. If you ever have an issue, the warranty covers your replacement, no questions asked.

Browse the complete lineup of vehicle-specific fuel pumps and order yours today at https://www.kemsoracing.com/. With fast shipping to the US and a customer service team that knows vehicles, KEMSO is the skip-the-headache choice for your fuel system repair.

The Bottom Line

Finding and replacing the fuel pump relay on a 2008 Infiniti FX35 is a straightforward DIY task that takes less time than changing a set of spark plugs. The relay sits safely inside the engine bay fuse box (IPDM E/R) next to the battery, clearly marked with a fuel pump icon. A quick continuity test with a multimeter can confirm whether the relay is the source of your no-start problem. And if you discover the fuel pump itself has failed, do not settle for an off-brand part—choose a KEMSO high-performance fuel pump with a lifetime warranty from https://www.kemsoracing.com/ to get your FX35 back on the road reliably.


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