The fuel pump is located near the right rear fender, and it makes a hissing sound when it's on...can't remember if it does this when starting though.
The OVP and fuel pump relay should be located behind the battery. They reside behind a black plastic shroud that is held in place by the firewall lip. Push it down, then out to remove.
The fuel pump relay is black, while the OVP is silver...the OVP has a clear lid on top with a AN type fuse inside (red or green, depending on model and year)...check the fuse first to see if it's OK before yanking parts out and replacing them.
2009 ML350 (84K) - Family vehicle
2001 CLK430 Cabriolet (71K) - Wife's car
2005 BMW 645CI (124K) - My daily driver
2012 Mustang V6 (60K) - Daughter's car