Nissan Mistral ignition problem 2.7 tdi?

Ok going to list what I have tried so far , battery checks out ok , all dashboard lights on glowplug etc , initialy when turning key , there is a fast clicking ticking sound , which maybe faulty relay ? glowplug relay ? this has not happened before ! not sure if it would start on a jump start if this is not working ? any ideas as to my theory of relay or alternative ideas seems electrical on ignition process ? , cheers in advance