When you turn the key to the on position, before cranking the starter, do you hear the fuel pumps cycle? It's a hissing sound from the rear of the car that last about 3 seconds.
2003 S500 Black/Charcoal
1990 560SEL 61k Arctic White/Grey
1988 420SEL Black/Palomino Sold @ 85k
1987 420SEL Midnight Blue/Grey
1986 420SEL Diamond Blue/Grey
1983 380SEL Champagne/Palomino