Cold starting problems

[Markssl]

My 2008 E320cdi is just coming up to 160k miles and runs superbly, apart from a new cold start issue. Turn the key after the glow plug lamp has gone out and it takes 4 full starting cycles to fire up. It's always started first time! I had all the glow plugs changed about 5k miles ago. When it finally starts I get huge clouds of white smoke out of both exhausts but more from the passenger side. And then it runs perfectly. No warning lights or messages. Start it again after its up to temperature and it fires up first time. I think it's cold starting with no help from the glow plugs and the smoke is unburnt diesel but I'm no expert. Also I switched off the other day and the engine carried on running but this has only happened once.
I'd be grateful for any advice.
Many thanks
Mark

 

[Dieselman]

Probably some air in the fuel pipes. Check the unions.