urgent help needed

this is my first thread, I bought a merc E 300 TD 1999 have had nothing but trouble with it since buying, got air bubbles trapped in the pipes, Have read on other threads that it would be air in the system realise i need to change all the o rings bought new battery cranked a few times to no avail, Still cant start the car, Now not even getting ignition lights in fact the only light on the dash that comes on is the air bag light. Petrol gauge not moving I think the car recognizes the key because the steering lock comes off and can hear noises sounding like pumps starting. everything in the car works apart from the heating the radio. I cannot find anything on the forum relating to my problems. Can anyone suggest why i may not be getting any ignition lights, Any help would be appreciated,