My car wont start and sounds like a machine gun?

So I just changed the PCV valve and my 1988 Ford Bronco was running great after taking it on a little test run. I then went to start it back up a couple hours later and it was just about to start and then suddenly it was as though everything electrical just died and now my car is dead. The headlights wont turn on and the only dim light i am receiving is my interior light. So i tried jumping it and when i did it sounded like a machine gun but would not start, but then once i removed the jumper cables, it went back to being completely dead and wont even sound like a machine gun anymore?????