injection problem

1998 2.2 cavilier running on three cylinders. Took off the fuel rail and only three injectors were spraying when i turned it over. so i bought a new injector still the same. so i tried pluging the old one injector into a different injector wire turned out it was'nt the injector after all. it seems like there is no power going to that injector. does anyone know if there is a sensor which controls the timing of the injectors or could it be the traction control causing my problems