Fuel Pump

The BMW E31 Fuel Pump is a complete, high-quality fuel pump assembly designed for the BMW E31 850i, 850ci, and 850CSI models with M70 and S70 engines (1990-1997). Positioned beneath the passenger rear seat, this assembly includes a top rubber seal and incorporates several key upgrades to correct common issues with the original design.

The primary issue with the original BMW fuel pump assembly was fuel leakage, particularly from the mold parting line located at the top of the unit. Over time, micro cracks formed, resulting in fuel seepage. The newly designed fuel pump assembly eliminates this issue by reinforcing the top cap for a more durable, crack-resistant structure.

Additionally, the original plastic preformed fuel lines have been replaced with high-quality, high-pressure PTFE corrugated fuel lines, making the system more resistant to modern fuels like E10 and ethanol. These new lines provide superior performance by preventing pressure leaks that were common with the older design.

For improved safety and longevity, the wiring has been upgraded to military-grade PTFE insulation, which is highly resistant to fuel and will not degrade over time. The fuel pump motors have also been redesigned, now using carbon commutators instead of copper ones. These carbon motors are quieter, more durable, and last up to three times longer than the original copper commutator motors, providing a reliable and efficient fuel delivery system.

Lastly, the fuel level sensor has been re-engineered with modern components for better precision and durability, ensuring a more reliable fuel gauge.

• Eliminates fuel leaks caused by cracks in the original design
• High-pressure PTFE fuel lines for enhanced durability and resistance to modern fuels
• Military-grade PTFE insulated wiring for greater longevity
• Upgraded carbon commutator fuel pump motors for quieter operation and longer life
• New pump motors deliver 150 LPH, offering improved fuel delivery over the original 110 LPH
• Re-engineered fuel level sensor for better accuracy
• Plug-and-play installation with all necessary components for a seamless fit

The Precision Raceworks G8x/G2x Stand Alone Auxiliary Fuel System is the highest-performing and most stable low-pressure fuel system on the market! Forget about how things have been done and embrace the benefits of dedicated fueling for your port injection!

Since direct injection came out for BMW, enthusiasts have been adding port injection.  With this came the need to upgrade the low-pressure fuel system to keep up.  Historically this was done by increasing the output of the main fuel system.  Unfortunately, the main fuel pump is controlled using PWM by a factory programmed controller designed to reduce output when target fuel pressure (typically 5 bar) is exceeded, creating a constant battle when pumps are added or upgraded.  This limits upgraded fuel pumps from performing to their full potential.

Additionally, the high-pressure pump control system dumps fuel back into the low-pressure system at high pressure low volume resulting in oscillations of the low-pressure fuel system.  Because of this, the DI system in the car is required to constantly make corrections to keep target AFR in check.

With this stand-alone low-pressure fuel system dedicated to your port fueling that is a thing of the past!  Get rock-solid fuel pressures at any pressure, run fuel pressures that are 1:1 scalable to boost pressure, flow more fuel with dedicated lines, run smaller injectors and still get more fuel than you did with large injectors (allowing for higher resolution), put less demand on the car’s DI system to correct for fluctuations in pressure, even your tuner will be grateful as the system makes tuning of port fueling even easier and more accurate, the list of benefits goes on and on!

Features & Benefits

Billet Aluminum top hat with 3 high-flow fuel ports

Dedicated fuel pump(s) for port injection system

Optimal pump location resistant to fuel slosh under acceleration

Fully adjustable 1:1 scaling billet fuel pressure regulator

10-micron USA made Microglass fuel filter (Ideal for E85)

Smooth bore high flow PTFE fuel feed & return lines (AN6)

All billet connections for both fuel line fittings and top-hat

Plug and play connectors inside and outside* the top hat

Configurable pump activation harness (see instructions for more details)

Increased injector flow (when using 1:1 regulator feature vs static)

Compatible with all stock or upgraded primary fuel pumps

Easily expandable and upgrade-able for more fuel

All components and parts feature 100% Ethanol Compatibility

The AFS.800 dedicated auxiliary fuel system comes with all** necessary components to provide dedicated fuel system for port injection.  Featuring Two Walbro 535’s (F9000295) fuel pumps with a combined flow of 800LPH at 3 bar.

Pump flow 43.5 psi-a : 800 lph

Recommended base pressure: 43.5 psi-g

Maximum Fuel Pressure: 110 psi-g

Number of Fuel Output Ports: 2

Number of Fuel Return Ports: 1

Pump 1: Walbro 535 (F90000295)

Pump 2: Walbro 535 (F90000295)

Available (unused) Electrical Connections: 2*

Total System Weight:14 lbs (including fuel lines and wiring harness)

*At time of install some wiring in the car may need to be cut and spliced to connectors included in this kit

**Male AN8-ORB to Female AN6-ORB adapter may be required for compatibility with some fuel rails (not included in kit)