I tried to put the pressure regulating screw back on without the spring and it wouldn't screw any further than it had been. Examined what I cleaned up and there is still a little bit of gunk in the threads. I think there may be more down inside, so that will need some attention. I don't mind the color difference, as probably that would be the correct position to actually sew.
Janey - Neat people never make the exciting discoveries I do.