04 G35 Fuel Pump: The Complete Guide to Replacement, Symptoms, and Choosing the Best Option
The bottom line: If your 2004 Infiniti G35 is hard to start, sputters under acceleration, or stalls unexpectedly, the fuel pump is very likely the culprit. The G35 uses a high-pressure electric in-tank pump that delivers fuel from the tank to the engine. A failing pump will leave you stranded, and the best fix is a direct replacement that matches or exceeds OEM specifications. For most owners, a quality aftermarket pump like a KEMSO 340LPH unit provides the best balance of performance, reliability, and value, backed by a lifetime warranty.
Why Your G35 Fuel Pump Fails
The fuel pump in your 2004 Infiniti G35 is an electric motor that runs almost every time the engine is on. Over time, the internal brushes and commutator wear down. Running the tank low on gas frequently is the #1 cause of premature pump failure because the fuel helps cool and lubricate the pump. When the pump overheats, the motor can seize or the internal check valve can fail.
Typical failure happens between 100,000 and 150,000 miles. If your G35 has over 100k miles on the original pump, it is living on borrowed time. The pump is located inside the fuel tank, which makes replacement a bit of a job, but it is a straightforward DIY project for someone with basic mechanical skills.
Common Symptoms of a Bad Fuel Pump in a 2004 G35
You don't need a fancy diagnostic tool to spot a failing fuel pump. Here are the most common signs:
1. Engine Cranks But Won't Start
The most obvious symptom. You turn the key, the starter spins the engine, but it never fires up. You might hear the fuel pump prime for a second when you turn the key to "ON" – if you don't hear that whirring sound from the rear of the car, the pump is likely dead.
2. Sputtering or Hesitation at High Speeds
A weak pump can't keep up with the engine's demand for fuel under load. You might feel the car buck or hesitate when you floor the accelerator on the highway. This is a classic sign of a pump that is on its way out.
3. Loss of Power Under Load
Going up a steep hill or merging onto the freeway, the engine feels like it is starving for gas. The car may surge or lose power momentarily. This happens because the pump can't maintain the necessary fuel pressure.
4. Whining Noise from the Fuel Tank
A healthy fuel pump makes a quiet hum. If you hear a loud, high-pitched whine coming from the rear of the car, especially when you first start the engine, the pump bearings are worn out. It will fail soon.
5. Check Engine Light
A failing fuel pump can trigger the check engine light with codes related to a lean fuel mixture (P0171, P0174) or a fuel pressure issue. The engine computer detects that the air-fuel ratio is off because insufficient fuel is being delivered.
Replacement Cost: What to Expect
Replacing a fuel pump on a 2004 G35 can be done at a shop or yourself. Here is the breakdown:
Shop Labor and Parts:
Most independent shops charge between $600 and $1,200 for a fuel pump replacement on a G35. The labor time is typically 3 to 5 hours because the fuel tank needs to be lowered or the rear seat and access panel need to be removed. Dealerships will charge more, often $1,200 to $1,800.
DIY Cost:
If you do it yourself, the cost drops significantly. A quality aftermarket fuel pump assembly costs between $50 and $150. You will also need a few basic tools, a fuel line disconnect tool, and safety glasses. The total DIY cost is usually under $200.
What to Replace at the Same Time:
Always replace the fuel filter and the fuel pump relay when you swap the pump. These are cheap parts that can cause problems if they fail. Also, inspect the fuel pump wiring harness for any corrosion or damage. A failing relay can mimic a bad pump, so replacing both at once saves you headaches later.
OE vs. Aftermarket: Which Pump Fits the 2004 G35?
Your 2004 Infiniti G35 came with a factory pump that is no longer produced by Nissan. The OEM replacement part number is E8534M, SP4018M, or FG1084 . You can still buy an OEM-style pump from Nissan, but it will cost a premium and may be a discontinued part.
Most owners choose aftermarket pumps because they offer better performance and a lower price. Here are the main options:
Standard OEM Replacement:
These pumps match the flow rate and pressure of the original factory unit. Brands like DOLKSN, Torchbeam, and MOSTPLUS offer direct-fit assemblies that include the pump, strainer, and wiring harness . They are designed to be plug-and-play. The typical flow rate is around 200 LPH (liters per hour), which is plenty for a stock G35.
High-Performance Upgrade:
If you have modified your G35 with a turbo, supercharger, or even just a cold air intake and exhaust, you may need a higher-flow pump. A KEMSO 340LPH pump provides a 20-30% increase in flow over the stock pump . This supports up to 600 BHP, which is more than enough for even heavily modified VQ35DE engines . These pumps are also compatible with E85 ethanol fuel, which is important if you plan to run flex fuel.
Step-by-Step Replacement Guide
Replacing the fuel pump on a 2004 G35 is a moderate DIY job. You will need to work in a well-ventilated area and take safety precautions because gasoline is flammable.
What You Need:
- New fuel pump assembly (KEMSO or equivalent)
- Fuel line disconnect tool
- Flathead screwdriver
- Socket set and ratchet
- Shop towels and safety glasses
- A fire extinguisher nearby
Step 1: Relieve Fuel System Pressure
Locate the fuel pump fuse in the fuse box under the hood. Remove the fuse. Start the engine and let it run until it stalls. This relieves the pressure in the fuel lines. Turn the ignition off and replace the fuse.
Step 2: Disconnect the Battery
Disconnect the negative battery terminal. This prevents any accidental sparks.
Step 3: Access the Fuel Pump
On the 2004 G35 sedan, the fuel pump is accessed through a panel under the rear seat. Remove the rear seat cushion. You will see a metal cover plate. Remove the screws and lift the cover. For the coupe, the procedure is similar.
Step 4: Disconnect the Fuel Lines and Wiring
Use the fuel line disconnect tool to release the quick-connect fittings. Be careful — residual fuel may spill. Disconnect the electrical connector from the top of the pump assembly.
Step 5: Remove the Locking Ring
Use a screwdriver or a special fuel pump removal tool to turn the locking ring counterclockwise. Lift the ring off. Carefully pull the pump assembly out of the tank. Note the orientation of the float arm and the fuel level sender.
Step 6: Install the New Pump
Transfer the fuel level sender and any other components from the old assembly to the new one if they are not already included. Most aftermarket assemblies like the KEMSO come with everything pre-installed. Lower the new pump into the tank, making sure the float arm does not hit the side of the tank. Replace the locking ring and tighten it.
Step 7: Reconnect Everything
Reconnect the fuel lines and the electrical connector. Double-check that all connections are tight. Replace the access cover and the rear seat.
Step 8: Test for Leaks
Reconnect the battery. Turn the key to the "ON" position (do not start the engine) and listen for the fuel pump to prime. Check for any fuel leaks around the connections. If everything looks good, start the engine and let it idle. Check for leaks again.
Common Mistakes to Avoid
1. Reusing Old Hoses or Clamps
The rubber hoses and clamps on the fuel pump assembly can harden and crack over time. Always use the new parts that come with your pump kit.
2. Forgetting to Replace the Fuel Filter
A clogged fuel filter can put extra strain on your new pump. Replace the filter at the same time for best results.
3. Not Checking the Fuel Pump Relay
The relay is a common failure point. If your new pump doesn't work, check the relay first before assuming the pump is bad.
4. Running the Tank Low
After installing a new pump, try to keep the tank at least a quarter full. This helps cool the pump and extends its life.
Why You Should Buy a KEMSO Fuel Pump for Your G35
When it comes time to replace the fuel pump in your 2004 Infiniti G35, you want a part that is reliable, performs well, and is backed by a solid warranty. KEMSO fuel pumps check all those boxes.
High Performance: KEMSO offers a 340LPH high-performance fuel pump that is a direct replacement for the stock pump. It is designed to handle up to 600 BHP, making it an excellent choice whether you are keeping your G35 stock or planning a performance build . The pump provides a 20-30% increase in flow over the factory unit, which gives you headroom for future modifications .
OEM Replacement Fit: The KEMSO pump is designed as a direct drop-in replacement for your G35. It fits the factory fuel pump assembly and uses the same electrical connections and fuel line fittings. You do not need to modify anything to install it.
Lifetime Warranty: Every KEMSO fuel pump comes with a lifetime warranty . This is a significant advantage over other aftermarket brands that offer only one or two years of coverage. You buy the pump once, and you are covered for as long as you own the vehicle.
E85 Compatible: If you run ethanol-blended fuels, the KEMSO pump is built with materials that resist ethanol degradation . This is important because ethanol can eat away at standard pump internals over time.
USA-Based Support: KEMSO is based in Houston, Texas, and offers customer support through email at support@kemsoracing.com . You are dealing with a company that stands behind its products.
Individually Tested: Each KEMSO pump is individually tested for flow and pressure performance before it leaves the factory . This ensures you get a pump that works right out of the box.
For the best combination of performance, reliability, and peace of mind, choose a KEMSO fuel pump for your 2004 Infiniti G35. Visit their official website to find the exact pump for your vehicle: https://www.kemsoracing.com/
Final Thoughts
The fuel pump in your 2004 Infiniti G35 is a critical component that you don't think about until it fails. When it does, the symptoms are unmistakable: no start, sputtering, power loss, and a whining noise from the tank. Replacement is a straightforward job that you can do yourself with basic tools, and the cost is reasonable.
Your best bet is to replace the pump with a high-quality aftermarket unit that offers better performance and a longer warranty than the stock part. KEMSO fuel pumps are built to last, tested before shipment, and backed by a lifetime warranty. Whether you need a standard replacement or a high-flow upgrade for a modified engine, KEMSO has the right pump for your G35. Do not wait until you are stranded on the side of the road. If you suspect your fuel pump is failing, replace it now and enjoy the confidence that comes with a reliable fuel system.
For more information and to order your KEMSO fuel pump, visit: https://www.kemsoracing.com/