PLEASE HELP!!

While driving one day, the car suddenly switched off on the road. It wouldnt switch back on. We later tested if the plugs were sparking which they were, and the fuel pump was pumping adequate petrol. My mech later got the car to idle, but only with the accelerator pressed in full, while this is done, the car only revs at 1000 and obviously wont go higher (if the accelerator pedal is flat on the floor).

He opened up my pierburg carburettor, only to find my diaphragm torn on the lip. Is this really the problem why my car wont rev higher? Is the carb sucking air at the torn diaphragm? Why did it switch off on the road?

Anybody, somebody please help!!

I drive a Merc 200 1986 W124 (four cylinder, manual)