What model of bike do you have? Have you tested that same voltmeter on your car.... to make sure it's not the voltmeter reading wrong?(reading higher than it actually is....).
Look under the passenger part of the seat and see if there's any wires that could be touching, also look around the swingarm area.
Now you say the first time it was a "faulty" fuel pump. Did you checkout every piece from the tank to the throttlebodies/carbs besides the fuel pump?
Jeff
My bike-2002 F4i-With OEM CCT......And no rattle
"Life would be boring if everyone was perfect"