I'm not sure I was clear about this. You acknowledge that there is a brief buzz with these fuel pumps and in your first reply you state that you should not hear any noise at all.

My '75 pump has that initial brief buzzing sound when you turn the key on and then it stops. The problem that I am having with the current pump on the B21 engine is that it does not stop buzzing. I turn the key to the on position and it constantly buzzes, an obviously malfunctioning fuel pump.

My mechanic is excellent and he does understand the Bosch fuel injection system very well. And from experience with my old pump on my 164e, when it did this exact same thing, it was a faulty pump and a new one corrected the problem. As we all know, these old Volvo's are pretty quirky and sometimes develop a mind of their own :)