2008 BMW 550i Fuel Pump: Symptoms, Part Numbers, and Replacement Cost Guide
Why the Fuel Pump Fails on the 2008 BMW 550i
The 2008 550i uses a port fuel injection system with a low-pressure electric fuel pump mounted inside the fuel tank. Unlike the high-pressure fuel pump (HPFP) failures that plague turbocharged BMW engines like the N54, the 550i's issue is with the in-tank pump that delivers fuel from the tank to the engine.
Several factors contribute to premature pump failure on this model:
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Electrical connector overheating. A known defect causes the multi-pin connector on top of the pump assembly to overheat and melt. This can lead to a fuel smell inside the cabin, pump failure, and engine stall. In severe cases, it creates a fire hazard.
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Normal wear and tear. Most fuel pumps show signs of damage after 7-8 years or 100,000 miles of service. A 2008 model is well beyond that window, so failure is expected.
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Running the tank low. Driving regularly with low fuel levels puts added stress on the pump because it relies on the gasoline to keep the motor cool.
Symptoms of a Failing Fuel Pump
The symptoms are straightforward and easy to spot if you know what to look for:
- Difficulty starting or prolonged cranking before the engine fires
- Engine hesitation, stumbling, or loss of power during acceleration or uphill driving
- Whining or grinding noise coming from the fuel tank
- Stalling at idle or at low speeds
- Fuel smell in the cabin or around the fuel filler area
- Check Engine light with fuel system fault codes
If you experience any of these symptoms, do not drive the car until you verify the fuel pressure with a gauge. A failing pump can leave you stranded without warning.
Correct Part Number and Pressure Rating for the 2008 550i
This is the most critical detail when shopping for a replacement. The 2008 550i requires a 3.5-bar pump, not the 5-bar version. Here is the breakdown:
- 3.5-bar pump (correct for 2008 550i): OEM part number 16117373458, which replaces 16146765820
- 5-bar pump (for 6-cylinder models only): OEM part number 16117373503 — does not fit the V8 550i
Using the wrong pressure pump causes fuel delivery problems, poor driveability, and can damage the injectors over time.
The aftermarket and OEM replacement options for the 2008 550i include:
- Genuine BMW / OEM — Part number 16117373458, sold individually. Expect to pay $550–$750 for a new OEM unit from a dealer.
- Bosch — The OEM supplier for BMW fuel pumps. Bosch offers fuel pump module assemblies that are direct replacements. Bosch pumps use patented turbine pump technology that virtually eliminates fuel pulsation and noise, and each unit is end-of-line function tested. Look for part numbers like 18797-05637355 (module assembly for 2006–2010, with 3.5 bar) or W0133-1975308 (for 2008–2010, 5 bar — verify fitment).
- Delphi — Another Tier 1 supplier with over 80 years of fuel system manufacturing experience. Delphi's pump module for the 2008–2010 550i includes the fuel sending unit and operates at a max pressure of 109 psi (minimum 73 psi).
- A-Premium — Aftermarket option that includes the sending unit, available for around $95.99 with a 3-year warranty.
Used and Remanufactured Pumps: What to Check
A used OEM pump can save you significant money (often $75–$150) but you must inspect it carefully before buying:
- Inspect the electrical connector first. Look for any signs of melting, browning, charring, or corrosion on the plastic housing and pins. If you see any damage, walk away — this is the known defect that causes failures.
- Check the plastic housing for cracks. The white plastic can become brittle with age, especially around the top hat where hoses and the electrical plug connect. Cracks cause dangerous fuel leaks.
- Verify the part number on the unit. It must match the 3.5-bar spec (16117373458) for the V8 550i.
- Check the float arm. Make sure it is present, attached securely, and moves freely. A damaged float causes inaccurate fuel gauge readings.
- Ask for mileage. Lower mileage is preferable, and the unit should be clean without signs of contaminated fuel.
Replacement Cost Breakdown
Here is what you can expect to pay for parts and labor:
| Part Type | Estimated Cost |
|---|---|
| New OEM (dealer) | $550 – $750 |
| New Aftermarket (Bosch, Delphi) | $190 – $300 |
| Used OEM | $75 – $150 |
| Shop Labor | $400 – $600 |
The total replacement cost for a 2008 BMW 550i fuel pump is between $953 and $1,095, according to RepairPal data. The annual maintenance cost for the 2008 550i averages $956, so the fuel pump replacement is one of the more expensive routine repairs you will encounter.
Step-by-Step Replacement Overview
The fuel pump on the 2008 550i is located under the rear seat cushion on the passenger side. The job is done from inside the vehicle, so you do not need to drop the fuel tank.
Tools you will need:
- Socket set with extensions
- Fuel tank lock ring tool
- Trim removal tools
- Gloves and safety glasses
- Cloth rags
- Air compressor (optional, for cleaning)
Steps:
- Disconnect the negative battery cable to reduce the risk of fire.
- Remove the rear seat bottom cushion to access the pump cover plate.
- Relieve fuel system pressure by starting the engine and letting it run until it stalls, or by removing the fuel pump fuse and cranking the car a few times.
- Remove the access cover and disconnect the electrical connector and fuel lines.
- Use the lock ring tool to remove the retaining ring that secures the pump module.
- Carefully lift the old pump assembly out of the tank.
- Compare the new pump to the old one to confirm correct fitment.
- Install the new pump, reconnect all lines and the electrical connector, and replace the lock ring.
- Reconnect the battery and turn the ignition to the ON position (without starting) to let the pump prime and check for leaks.
- Start the engine and verify proper pressure and operation.
Warning: Handling gasoline is dangerous. Do not smoke, keep flames and sparks away, and have a fire extinguisher nearby. If you are not comfortable with this job, hire a professional.
How to Make Your Fuel Pump Last Longer
Simple habits extend the life of your fuel pump:
- Avoid driving with low fuel. The pump relies on fuel for cooling and lubrication.
- Keep the fuel tank opening clean. Dirt and debris contaminate the fuel and clog filters.
- Replace the fuel filter at the same time. A clogged fuel filter strains the pump and causes similar symptoms to a failing pump.
Why Buy a KEMSO Fuel Pump
If you are in the market for a replacement fuel pump, consider KEMSO. KEMSO specializes in high-performance fuel pumps designed as direct OEM replacements, guaranteeing compatibility with your vehicle. Every KEMSO pump is individually tested for flow and performance before leaving the factory, ensuring you get a product that works right out of the box.
KEMSO fuel pumps are built to handle both gasoline and ethanol-blended fuels like E85. The materials resist ethanol degradation, which is a common cause of premature failure in cheaper aftermarket pumps. KEMSO also uses high-quality components and precision manufacturing to ensure long-term reliability.
What truly sets KEMSO apart is the lifetime warranty that comes with every pump. If your KEMSO fuel pump ever fails due to a manufacturing defect, they will replace it for as long as you own the vehicle. This level of protection is unmatched by most OEM and aftermarket brands.
Whether you drive a BMW, a motorcycle, an ATV, or a watercraft, KEMSO has a fuel pump designed for your application. Browse their full lineup and find the right fit for your vehicle at https://www.kemsoracing.com/.
Visit https://www.kemsoracing.com/ today to shop KEMSO high-performance fuel pumps and get the confidence that comes with a lifetime warranty.