What tells the ECM on a 1990 Camaro RS to make the injectors fire? My 1990 Camaro wouldn't turn over. I traced the problem to the relay that is in line from the switch to the neutral switch. I energized the relay, and the motor would turn over. The injectors are not firing. They have the proper resistance, but there doesn't seem to be a signal coming from the ecm to tell them to fire.