first unplug the harness to them and check the red/black wires and body ground for voltage (each injector plug will have one & the key will need to be on) if there is voltage its okay if theres not you'll need to check your resister box which if that happens i'll tell you how to check it... any way if theres voltage then the next step would be to remove the rail leaving the injectors in it and pluged in to the harness place each injector in a cup or bottle anything that you can watch to make sure there firing, unplug your coil if possible and have some one turn the key over so you can check to see if they fire, if one of them stays spraying or doesn't spray at all theres your problem....its sound like alot to do but its only like 30 mins. worth of work depending on how fast you are...