There's 2 connections on each injector wire, live 12v+ then the other is switched ground by the PCM/ECU Need to check that one is power when cranking if you have power then check with the noid light the ECU switching when cranking , if the noid light does not flash at all when cranking you really need a wiring diagram to see where the fuses and relays are.

I'm sure with a bit of you tubing you can find step by step guides how to do it.

Looking again at that wire looks like a ground wire thats snapped/corroded off , see where it reaches you'll find where youve snapped it off from .

Further than that you;ll need to get the fault codes rread, might give you more of a clue, but be weary that there maybe lots of codes that have been man made during your 3 yrs job.