S13 blacktop, #4 injector not working

[BallzDeep1.9L]

heres the deal (yes i did a quick search and didnt find anything one this problem).. thre is no power in the #4 cylinder on my friends S13 blacktop, and there is no gas on the spark plug, .. this is everything that we KNOW is good/ or have already done

1. igniter is good

2. coil is good

3. spark plug is good

4. swapped a new injector plug on when we noticed that the wiring was pulled out some, and the metal connectors were showing from the one that was on there, (thought we had it this time but it still didnt fire) but we know for sure that the plug we put on was good

5. injector is working properly (swapped it with the #1 cylinder injector and the #4 cylinder still had nothing)

6. tested continuity from the harnes plug to the injector plug and it has continuity

7. in a last second thought was tried individually grounding that injector by itself and still didnt work, maybe this was a stupid thing to do, i dont know.. im not a sr20 expert.. just trying to eliminate any possibilities

8. his buddy has a spare S13 blacktop ECU, we will be using that tommorow to see if the ECU is the problem

now heres the thing.. i found a pinout diagram for the ECU.. there are only 3 injector ground wire pinouts listed.. i would think that if each one is grounded back to the ECU (maybe thats how the computer controls the firing of the injector, again i dont know, im not an SR20 expert) it would have 4.. if it HAS to be grounded back to the ECU then we are either down to the ground wire being fried by the contacts on the plug touching each other ..OR it fried the ECU..shorting out.. either way im up a creek without a paddle.. could PLEASE use some help here.. thanks guys