help please

my 300 tdi starts fine every day, but if i dont start it for more than 3 days its a real sod to start its had an oil and filter change and new glow plugs when it eventually starts it seems to run on 2 cylinders and white smoke billows out the exhaust then after a couple of minutes its all fine.
any ideas
ginge

You have an air getting into your fuel system and that is allowing the fuel to seep back down the pipes towards the tank. Check all fuel pipes. The small leak off pipes joining the injectors to gether is a really common fault with diesels.