Starter wiring question

[jackbombay]

So here is a pic of how the starter was wired up to the gas motor when that was in the car,



  My question is what is the black wire for? It is not listed in the bently, and it disapears into the main wiring harness, the black and red one is from the ignition switch and the other 2 large red ones are obvious, but I don't know where the black one goes as there is no terminal for it on the Diesel starter. I assume it is something gas engine specific, but I am puzzled that there is no mention of it in the bently.

  The car is a VW Quantum Syncro, 5 cylinder, 86'.

  Thanks, Jack

[QuickTD]

The extra wire is usually for the resistor bypass circuit or "hot start" as it is sometimes called. It sends 12 volts directly to the ignition coil, bypassing the  dropping resistor. Battery voltage (and spark energy) drops during cranking, this setup helps increase voltage to the coil to provide a hotter spark while cranking.

[jackbombay]

Great, thanks for the info, the best part is that the soultion is "do nothing"