I was noticing a buzzing sound coming from the rear and thought the fuel filter must be clogged and the main pump working overtime to compensate. When I went under to replace the filter I noticed the secondary fuel pump and thought it might be the source of the sound instead, and indeed after starting up the car, a distinct high piched buzz could be heard coming from the secondary pump.

I gripped the pump tightly to make sure it wasn't just a vibration but the buzz persited from inside the pump itself. Does this sound indicative of a malfunctioning pump or could it be working overtime due to a bad fuel filter as I had suspected of the main pump?

Is there any other concerns I should have regarding the sound this pump is making, and how much of a risk is being taken driving the vehicle while this condition persists?