UK Car Repair: 1.7 Opel diesel 1996 starting difficulties, track thanks, opel

Question
The engine requires lots of cranking to start, even when hot. The heater light comes on and goes off normally, and once the engine splutters into life it runs fine. I suspect air but I can't find a bleed nipple. Am I on the right track?
Thanks
Mike

Answer
Almost, it is a lack of fuel, the first thing I would suggest is to change the fuel filters, the main one, in, or close to the tank, and the secondary one near the engine injection pump. If in fact they are OK, I would suspect the supply pump is the problem.