2001 Mercedes E320 W210 4Matic Cranks No Start


As title states, my '01 Mercedes E320 4Matic W210 Sedan is having some intermittent problems where she'll crank and crank but not actually fire up. I'e noticed when this happens I'm not hearing the fuel pump engaging like I normally do. Narrowing down the problem hasn' been easy. Some say could be the Crank Position Sensor while others say it' a Fuel Pump Relay or Fuse. Has anyone else experienced this prob and if so, how'd u fix it?