When starting this machine up in the morning it fires first time every time but when operator stops for first bait the machine will not fire back up, it will just keep turning over but won't fire, now if you leave it for another half an hour or so it will eventually start. All fuel lines are fully primed and filters have been changed. Has anybody any idea of what the problem could be??
Sounds typical of a common rail engine with a leaky injector/s or pump failing.
Second that. Rented a 320D one time. Had under 1000 hours. Was doing the exact same thing. Ended up being the high pressure (I believe) fuel pump. They had to pull the engine out to get to it, while we had it in the field. It got to where it would not start at all.
As Cmark says, the perfect signs of a common rail engine building up internal leakage. Without intervention of some sort it will soon get to the point it won't even start when cold. At least right now you have the advantage that it does actually run, try diagnosing one that's got so bad it won't even start. Although it goes against my principles to simply throw parts at a machine in the hope that it will fix the problem in this case as a first step I would go ahead and replace the rail pressure relief valve because a) it's not expensive and b) it's pretty much guaranteed to be fcuked anyway.... How many hours are on it..?