Hi Mate
I know this might sound redicules, but my local garage tried to tell me my fuel pump had gone.
I watch them trying to start it up for an age with easi start. Called back the next day to find the Boss had had a go at it and got it going.
Fault being an air leak on the fuel filter housing. Are you sure fuel is getting there? It could have cost me for bad diagnosis.
Sorry if I'm talking nonsense. 
Not at all, I don't know much about the diesel so need as much help as possible 
Me neither, but I do know about Oil Boilers

you can have the same problem on suction lines.
I know how much trouble my local garage has had after they have done work on the fuel lines and filter. It's essential the line and joints have no leaks, they don't show as leaks, but under suction rather than pull fuel they draw air in instead. (No Fuel Suction)
Also when the pump is stopped air leaks can allow the fuel to run back to the tank. Instead of holding in the pipe. A bit like when you put your finger over the end of a straw. I could be barking up the wrong tree, but must be worth a try

I had the return lines chanced on my older 2ltr DTI because of they thought that was the problem a few years ago. It turned out to be a cracked fuel filter housing.
That car just turned 200,000 miles last week. Not bad for an old en
