Return style fuel system with OEM fuel pump activation
When switching to a return style fuel system a lot of people just wire the pumps to key on power. This has some major downsides.
- Anytime the key is on the pumps are running and draining your battery. Think about getting a wheel alignment or when flashing on a tune etc.
- Safety issue like when you crash or the car stalls and the ECU would like to turn off the pumps but cannot.
To keep the ECU in control of your pumps have your tuner adjust the tune for a return style fuel system and keep the FPDM (fuel pump driver module) in use. Use pins 3 and 10 to activate the relay(s) that will turn on your fuel pumps.
Pin 10 = BN/PK (normally fuel pump positive) Pin 3 = RD/BK (normally fuel pump negative)
Don’t just use pin 10 positive power to your relay and ground the relay to the chassis. That won’t work. You must use both pins 10 and 3 to trigger your relay.
The FPDM pinout for reference