So I checked to see if I had pressure in the rail and it appears I do. I'm not sure how much because I couldn't find the proper fitting for the fuel pressure gauge.

We took the fuel pump relay out and hooked it to a power supply and tested it and it seems to be working ok. The fuel pump will prime with the ignition on but after it primes it shows 0.0 volts on both wires to the pump.

Me and the mechanic concluded the relay is the likely suspect so I have ordered one from Mercedes and it will be here Thursday. Hopefully this solves my issue. Will confirm once I put it in.