i had massive problem with my Z injectors,
car woudnt fire.
are none of them injecting/clicking?
to test if they were clicking, i removed the CAS (crank anlge sensor) while its still connected, spin it by hand, to hear them clicking.
you just want to trace how far the power/earth is getting from the car to the injector,
e.g. the negative signals may be coming from the ECU, but getting lost in the loom (like a break/cut wire)
it turned out on my Z that the conectors on the loom were awfully coroded, so the signal wasnt getting from the ECU to the injector.
that wont work, you need a Noid light to test the injectors (fiver on ebay)
check the ECU, CAS, power suply, PTU/ignitor pack,