Yep vnv8driver started this bullshit and its spread like wildfire its the most misinformed thing about oil switches going around i wish every instance of this statement could be erased. ive run plenty of motors without an oil switch plugged in or even there using a pressure gauge instead
that is correct, on VN/VP the fuel pump has 2 supplies, one switched from the ecu through a relay and another through the oil pressure switch. for the VR and VS however they did alter the wiring a little. for the VR/VS the fuel pump is powered through the relay only. when the ecu switches the relay the fuel pump is powered from fuse No:23. if the ecu hasn't switched the fuel pump relay on then the fuel pump is powered through the efi relay and fuse No:10 through the oil preesure switch (when there is oil pressure). the fuel pump relay is wired NO (normally open, so requires a closed circuit) from the ecu. the oil pressure switch is wired to the NC (normally closed) side of the fuel pump relay.
check this link to see what i mean
VR wiring diagram
however, the trick question is, does the ecu on the VR/VS maintian a complete circuit to power the fuel pump once the car is running or does it only "prime" the pump before starting the car? might have to check this out on the missus VS i think
edit, just been out and tried this on the missus VS, run engine and then removed plug from the oil pressure switch. engine kept running. so this means that the ecu keeps the relay closed and powers the fuel pump.
so it is a complete myth about the oil pressure switch. i do however beleive that the "roll over/accident" protection by powering the fuel pump through the oil presure switch is what holden was intending to do, however they stuffed it up when they use the ecu to run the fuel pump relay when the engine is running, it should have been designed is such a way that the ecu only primes the fuel pump (when starting the car) and then the oil presure switch takes over once the engine is running. maybe they got it right in later model cars, for the VT the oil pressure switch is wired directly to the ecu so in theory it might work. anybody with access to a VT want to find out?