intermittant non starting
 

hi. new to the forum, but my a6 saloon 1.8t is doing my head in! it is a 2000 model with the engine code apu. some times will just not start, you get in turn on ign and if no epc light appears on the dash the fuel pump does not make a noise and therefore will not start, just turns over and over. so you just sit there for ages turning the ign on and off until suddenley hey presto! the epc light appears on the dashboard the pump makes a noise and it starts! once started it is no problem, no missing, no lights coming on, although it does tend to smoke quite badly for maybe 5 mins' tried to put code reader on but no communication when it wo'nt start when started it showes 2 codes, boost pressure valve open circuit and control mod rom error any body got any idea's