My 2009 a6 2.0 diesel will start reliably in the coldest weather but will invariably not start when engine is warm. It turns perfectly but within 1 second engine cuts out. It used do this 2 to 4 times before starting and I tolerated that, but now it can take up to 20 attempts. Then, after several attempts, for no obvious reason it starts and drives normally. This has been going on for months. It has never actually failed to eventually start. It is the 134 bhp model with 160,000 miles done.
Can you help please?