The weird thing about the noise is the intensity of the sound changes according to the electrical load. When you put on the turn signal it changes sound along with the flash. Same thing when you hit the brakes and the stop lights come on. Any ideas?
The sound is changing because the other stuff is drawing current, which is causing the voltage to the pump to sag just a bit.
You can measure the voltage at the FP fuse, in the fuse box.
With the box snapped up in it's normal position, it'll be the dark read fuse, nearest the edge of the dash, 2nd from the left.
If you REALLY want to be accurate, you can measure the voltage at the yellow plug, on the firewall, just above the tank. I forget which wires, though.
If the voltage is too low, it will cause the pump to draw excessive current. (Too low voltage can be as damaging as too high voltage, over time.)
I noticed that one of the fusible links had been replaced. If there's a bad connection on that link, it might be what's going on. The fuel pump fuse is always hot. So is the feed for the headlights, and lots of other stuff. I had that same link to act up on my car. A replacement fusible link had a bad connection that eventually failed. (Mine was the big red wire that disappeared under the sail panel, and went to the whole front of the car.)
