I have read that the fuel pump looks at the rpm and if its less than 300 rpm, it will shut off. Since you are having tack problems, it could be reporting an incorrect rpm to the fuel pump, in fact it could be oscillating around 300 rpm very rapidly causing it to turn on and shut off rapidly cauing the buzzing you mentioned.
2000 C230 Kompressor
1988 190e 2.3 - 225K miles, owned for 7 years. I cannot say enough good things about this car. Very well built, even at 225 it ran like new.