Those test lights are crap by the way, and are almost worthless as a troubleshooting tool. Use a multimeter so you can actually get useful information that can help you.

You you aren't actually sure whether the ECU is turning the injectors on I assume. All four injectors get power all the time, and the ECU completes the circuit to ground to turn on the injector. So if you're just looking for 12V at the injectors, all you know is that they are getting power; you don't know if they are getting turned on by the ECU or not.

It's possible you have a problem with the OBD0-OBD1 harness or have the wrong harness. I think there are a few OBD0 connector pinouts if I remember correctly, but I'm assuming you know enough about your car to get the correct one so I don't think that would be a problem.