series one? must be green and yellow not white? just checked on wiring diagram for you,that wire goes to pin 20 on your ecu, i doubt very much it will be the problem, just so you know its the dizzy that triggers the coil to spark and not the other way round believe it or not, although you say you have a new dizzy that dont mean it cant be faulty,ive had that before in the past, worth trying another if poss as they are very prone for this problem, other thing id check is the earth wires next to the left of the heater box,one is the earth for the heater blower and the other is the earth for the ecu,if you have the heater box removed and that earth isnt connected you will have no spark.

hope this helps...