My mates audi a3 140 tdi doesn't start sometimes, he notices that if not used for a day that in the morning it doesn't start. It's been to the garage twice and £500 spent and it still does it. He gets it to start using easy start but said he had to have the accelerator fully down. So it is a fuelling issue, I was thinking maybe a tiny fuel leak then pressure dropping, but I've told him about priming it a few times before starting, yet it still didnt start without easy start. Anything obvious?