1994 thunderbird

I have a 1994 ford thunderbird with the 4.6 v-8, that seems to be having problems with the fuel system. As of right now it runs only on the left four cylinders. This is because the four fuel injectors on the other side are only dumping fuel at a constant rate. I disconnected them and checed them with a test light. They are getting constant power and constant ground. I checked the side that works properly and the ground for each injector is intermittant, where it alternates between on and off. Could any one tell me why I would have this problem, and why it would only affect the right four cylinders.