Your o-rings are worn and compressed and you should change them out while you have the injectors out. They don't cost much and are easy to change. Did you notice any fuel or staining on the intake below the loose injector? If so then you were losing pressure there. If not then the problem is either the pump or regulator, more than likely. If an injector pintle is stuck open and bleeding down into a cylinder, you should see some black (fuel) smoke on start up. Hope this helps.