Also, the constant +12volt supply comes from the relay under the dash(can't remember the colour), all the injectors are connected to this same supply. There is a fuse for this also. It's the one right next to the yellow fuel pump relay and fuse that you've already checked.
If it is getting +12Volts, i'll have to go away and have a look at some old posts and diagrams as I can't remember much about the earth side off the top of my head. Hope this helps.