Hi guys and gals. Got a starting problem on my 200 engine'd 300 tdi. I've done a search and looked into the spider unit, I tried earthing the orange/black wire that runs to the starter relay to no effect. Basically when I turn the key I hear a relay click in the passenger footwell and thats it. The lights don't dim as if it's even sending power to the motor, put a volt meter accross the battery to confirm its not dropping so it would appear the starter isn't getting power. If i put a bar accross the starter it fires up so is there something i'm missing with regards the starting circuit? I was even stood with the haynes manual and the starting circuit seems straught forward enough so I'm stuck.

I say intermittent as sometimes it fires straight away on the key

Super, you may find that there is a bad connection on the starter solenoid, the wire that runs from ignition/starter key has a female spade coupler on it, it gets "cooked" because of its position under the exhaust manifold and can lose connection even though it is still plugged onto its counterpart, high resistance = no voltage flow.
Solution, fit a relay in the start circuit, a fused 12v supply direct from the battery + and use the original wire to the solenoid as an activation source for your 15 amp relay, (spotlight type relay), and a wire from relay to the solenoid.
I have two 300 Tdi's here, a '97 and a '98, and I have fitted start relays to both because they both had intermittent starting failures from time to time, both have never failed to turn over since fitting the relays. Gaz