Is it the primary fuel pump?

[Pondy]

So we know that an E89 makes all sorts of noises during it's "going to sleep" process.

When you open either door I am presuming the initial whirring is the primary fuel pump priming and pressurising for an engine start...is this right?
So after about 5-10 minutes of leaving the car, it does the same type of whirring noise (makes me jump if I'm in the garage and all else is quiet). Is this the fuel pump reversing to relieve the fuel pressure? Sounds like the noise comes from near the rear wheels, so makes sense to me.

But then many things make sense to me but no-one else and vice versa

 

[Scubaregs]

Are you sure it's not your hardwired rampant rabbit powering down?

 

[B21]

The whirr is the secondary low pressure fuel pump in the tank pressurising the input to the HPFP which is mechanically driven off the engine,…so it’s not possible to hear the primary pump running without the engine…this applies to N20 and N54 engines..

The N52 is port injected so I think that only has a single pump..low pressure in the tank..

I’ve never hung around long enough ( in a garage..sob..) to hear it shut down…

 

[Pondy]

The whirr is the secondary low pressure fuel pump in the tank pressurising the input to the HPFP which is mechanically driven off the engine,…so it’s not possible to hear the primary pump running without the engine…this applies to N20 and N54 engines..

S'what I meant. Primary as in 'the first one' from the tank. The LPFP, not the one that pumps it up to 5 million psi.
Just not sure if it reverses to relieve the pressure on shutdown.

 

[B21]

The whirr is the secondary low pressure fuel pump in the tank pressurising the input to the HPFP which is mechanically driven off the engine,…so it’s not possible to hear the primary pump running without the engine…this applies to N20 and N54 engines..

S'what I meant. Primary as in 'the first one' from the tank. The LPFP, not the one that pumps it up to 5 million psi.
Just not sure if it reverses to relieve the pressure on shutdown.

Pedantically..convention dictates that the fuel pump closest to the engine is the primary..so in the E89 on the N20 and N54 with DI that’s the primary…on the N52 with port injection the fuel pump in the fuel tank is the primary,..

But in any case the only fuel pump running prior to engine start is the one in the tank..