Ticking noise?

Hi all and before everybody starts telling me to search threads i have and found nothing to explain what the noise is so here it is... Its a 05 SD with 34000Km
On start up with NO revs, starts ok
Now a ticking noise comes every 10-20secs and keeps ticking
Can anybody shed some light on what it is? Is it normal?
Also at tick over its struggling to keep lit...
Maybe its all in my head or maybe not
Thanks any info would be a help

OB

All the motorcycles I have ever had make ticking noises... I figured it was normal. Valves and what not.

Yea im the same but the noise is a little stranger, I can here the valves ticking away not a bother but this is a little louder i could hear it when i went around the far side of the house to open the gate? That is a little odd to me... its like the ticking noise when the engine is cooling down but at regular enough intervals when at idle...

A BOMB!!!! Oh no NOT a bomb!!! Thats some good mechanical work from you, i hope your a mechanic because your wasted if your not... Actually no its all clear its not a bomb its a ticking noise coming from the engine, sorry keep your day job your a brutal mechanic ha ha