Fuel System

Fuel Pump Upgrade

The OEM Porsche fuel pump can provide enough flow and pressure for a V8, but there has been a high number of failures of the OEM pump. So a fuel pump upgrade is recommended. The kit below will use the stock wiring connectors and the spacer will fit the swirl pot housing. It is designed for a Turbo or C4, but can work with a C2.

Radium Engineering Porsche 911/996 To Walbro F90000262 Fuel Pump Install Kit (w/ Sock No Harness)

For a C2 the inlet will not sit in the correct place and the pump can be installed higher than normal or a hole can be drilled in the bottom of the swirl pot at the inlet. The mesh at the bottom may also need to be modified.

Return Fuel System

The 1999 through 2001 Porsche 996 uses a fuel system with a supply, return, and vent line in the engine bay. There is a fuel pressure regulator as part of the fuel rails. To get the correct pressure for the LS3, you will want to cut the fittings off rubber fuel hoses and connect them to a C5 Corvette Fuel Pressure Regulator using push on quick connectors, 3/8" quick connect and 5/16" quick connect. There are two fittings on one end, the 3/8" is supply and the 5/16" is return. The single fitting on the other end will go to the fuel rails. I recommend then using -6 AN lines to aftermarket fuel rails like these from Holly The stock fuel rails have a crossover that goes over the intake and will hit the top of the engine bay. Aftermarket fuel rails have the crossover on the back. I recommend that you add a fuel pressure gauge so you can tell if the pressure is the 58-60 psi you need. You will need a 1/8" NPT to -6 AN adapter for the gauge. The vent line can be capped off or run to an EVAP purge solenoid. The purge solenoid can be controlled by the GM ECU and goes to the intake vacuum port.

For more details, see this guide by Matt MacFadden @projectporvette

Fuel System Guide 996 from 1999-2001

Returnless Fuel System

The 2002 and later Porsche 996 and 997 use a returnless fuel system. There is a supply line and a vent line in the engine bay. The fuel pressure regulator is part of the fuel pump in the fuel tank at the front of the car. You only need a 5/16" quick connect to -6 AN adapter and a -6 AN fuel line to aftermarket fuel rails like these from Holly The stock fuel rails have a crossover that goes over the intake and will hit the top of the engine bay. Aftermarket fuel rails have the crossover on the back. I recommend that you add a fuel pressure gauge so you can tell if the pressure is the 58-60 psi you need. You will need a 1/8" NPT to -6 AN adapter for the gauge. The vent line can be capped off or run to an EVAP purge solenoid. The purge solenoid can be controlled by the GM ECU and goes to the intake vacuum port.

In the fuel tank, you will want to remove the fuel pump and replace the fuel pressure regulator. You will be replacing the 3.8 bar (55 psi) regulator with a 4.0 bar (58 psi) Bosch regulator. You may need to cut a notch in the clip that holds the regulator to install the new one. You can potentially skip changing this if your engine tuner can deal with lower fuel pressure. Most OEM and aftermarket LS engine tunes will be setup for 58 psi and will run lean with 55 psi.