VW Beetle 2002 1.9tdi engine troubles?

I have a 2002 (52) Beetle 1.9tdi. Several weeks ago starting having a intermittent fault where engine would just die. I had mechnic look at it- changed fuel filters and cleaned lines and checked fuel pumps. No error codes on diagnostics. Could find no problems, however problems perisited. I spoke to VW and suggested changing relay 109, which I have done. The problem is now not intermittent, but the engine won't fire at all. its as if there is no fuel....... Any ideas?