5th injector wires Black/yellow tracer.....Brown/white tracer...correct, someone may have fitted new plug itself, as the original would have been Blue.........all colurs of plugs are....Blue 5th.....Yellow water sensor....Brown Thermotimer.......Black....Cold idle valve......Green...Knock sensor [ very late cars ]....for your help Daz. Pete..........axel stands all ok.....yes 12v pos will be live on Black/yellow on cranking only....Brown would have been original controlled from Timer....but your saying been messed with, so yes it has to be NEG - on again cranking a Cold engine, ....once you get engine up and running that Timer circuit needs to be put back to standard.