Infinit,
The Overvolt relay is:
Under the hood, facing the car, at the rear passenger side, under the black plastic panel. There should be a silver rectangular metal peice with a fuse on top of it, this is the OVP. Make sure that when you get the new one, you buy the updated part, just ask if you have any questions.
As for the fuel pump relay, I need to figure out where this is also. I have heard that is next to the OVP, but still cannot locate it. Perhaps someone else coudl help?

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2006 E350 w/ 155k miles (Daily Driver)

Previous:
1993 300E 3.2L Sedan w/ close to about 300k miles
2003 E500 Brilliant Silver (Had 217k miles when totalled!)
1989 300E with 289,000 miles (had for <1 yr while in HI)
03 CLK 500 cabrio (Mom's)
2006 C230k (Dad's)
1999 S420 (Mom's/Dad's)
2000 C230k Sport sedans
2001 CLK320 Cabrio (Mom's)
1995 C280 My First Mercedes-Benz... (155k miles. EXCEPTIONAL AUTOMOBILE. Was Very hard to let go of!)