I have a very hard starting 560sl. I have had my mechanic completelly tune up with plugs, wires, cap, rotor, all filters as well as injector cleaner in fuel. I runs like a top in fact more power than every. The problem is it started very hard prior to tune up and now it is getting to either grind and grind or shoot either to start. Once warmed up runs great, will restart fine but does idle very slow 500 rpm and rough. I have been told perhaps one of the fuel pumps is down but I do not understand why that would effect the start as it does run down the road great. Any suggestion would sure help as I am new to this.