There are several starting issues with the diesel Rangie.
If it's the in-tank pump then it normally happens when the tank is less than a quarter full. Above about this level the weight of the fuel seems to push it through. A simple test is to take off the fuel line under the bonnet, get some-one with a container to catch the fuel, and crank the engine over. You should get a good spurt of fuel. A feeble trickle, or nothing at all, and your pump isn't operating.
If that's not the problem then the next port of call shopuld be the wee leak-off pipes that run from injector to injector. A leak on one of these can cause problems.
Next would be the glow plugs, but they show up more if it doesn't want to start from cold but it's a lot quicker to fire up when warm.