If it starts, it'll start all day long, if it doesn't it fires up for a second or two, dies and then if the battery lasts long enough I have to crank it and crank it, eventually firing on one then two then runs, it's like it starts on the fuel remaining in the high pressure pump /rail then runs out of fuel until eventually more arrives, it's been suggested the lift pump in the tank may have failed but there are no warning lights on, no codes stored and once it starts it runs fine all day, generally it'll start if it's been run in the past 24 hours or so but leave it a couple of days and it's a pig.
So far, service including fuel filter, new battery. any suggestions would be appreciated, oh and idle isn't smooth and occasionally I get the dumper truck idle when it's been run and idling for a while. other than driving me insane it's a lovely car, Audi A4 B7 2007 2.0 TDi S-Line Cabriolet