Cold Starting Mechanism

[carlioll]

I would be interested to learn how the cold start system works on a diesel bongo. I am talking here about the normal single battery vehicle and not the twin battery winter pack ones. The reason I ask is that when the vehicle is cold there is a squeaky noise coming from somewhere but only on tickover. It sounds like the alternator and when I sprayed WD40 on the belt at the alternator the noise did diminish for a while but returned. However, when the engine warms I hear a click like a relay or solenoid activating. The revs then drop to about 750 and the squeaky noise totally disappears. So my question is - are there any moving components on the cold start system and if so, what are they? Non of this affects the performance of the vehicle, its just that I dont like noises which I can't trace.
Cheers Keith