Fuel pump relay. Porsche 986 Boxster / 996 / 996 Turbo 99661510100

Fuel pump relay.
The fuel pump relay is a precision replacement relay for the fuel-pump control circuit in the Porsche 986 Boxster and 996 911 (including Turbo and early Carrera GT) models. This relay controls the activation of the in-tank fuel pump, providing the necessary current to ensure correct fuel delivery under demand - making it vital for engine start-up, steady fuel pressure and safe operation.

Fits:
Porsche 986 Boxster 1997 - 2004
Porsche 996 C2 / C4 / C4S 1998 - 2005
Porsche 996 Turbo 2001 - 2005
Porsche 996 GT3
Porsche Carrera GT 2004 - 2006

* Please check and match the part number of your relay in your car before ordering.

• Position: Mounted in the front luggage compartment fuse/relay panel or subsystems - controls power feed to the fuel pump relay circuit.

• Function: When the ignition is turned on or engine is running, the signal from ECU or shift lever energises this relay, sending current to the fuel pump so fuel pressure builds before engine cranking - crucial for proper fuel system operation.

• Applications: Ideal when the original relay has failed, is intermittent, shows corrosion on contacts, causes fuel-pump drop-outs, engine stumbling, or fails the self-check.

The fuel pump relay is a critical yet often overlooked part of the fuel delivery system.
A failing relay may manifest as:
• Engine cranks but won’t start (fuel pump never powers)
• Fuel pump prime is silent when ignition is turned on
• Engine stalls at random after start due to loss of pump voltage
• Intermittent “no-fuel pressure” faults or ECU logged errors

Replacing the relay with a correct unit ensures the fuel pump receives the proper current, realises full system pressure, and avoids mis-diagnosis of fuel pump or ECU faults.

When to replace:
• Original relay is over 10 years old, exposed to heat or aftermarket modifications
• You’ve installed a new fuel pump but issue persists (relay may be the culprit)
• You’re diagnosing no-start or stall symptoms that point to fuel pressure drop-out
• You’re restoring or prepping your vehicle and want to replace all wear-prone electrical relays

Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.

99661510100

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