[TMc993]

If the noise you are hearing is coming from slightly right of the centerline of the car and if, when you are in the car, the noise seems to emanate from the passenger-side foot well, it is the fuel pump.

If I remember correctly, when you turn the ignition on, the fuel pump runs momentarily to pressurize the system, but then does not actually run continuously until the engine is started. So, it is logical that you would not hear the pump running in the ignition-on-but-engine-not-running mode.

While a buzzing pump isn't a good thing, it isn't necessarily a sign of immenent failure either...Mine has been buzzing for over a year and the car runs fine....Yeah, it'll fail eventually, but all fuel pumps fail....Eventually.