timed click/clack every 7 seconds while idling. then stalled. now wont start

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My car was running fine except a weird noise, like a faint tick last few weeks.. today the car started making a click/clack noise.. it seemed to be timed while idling. 2,3,4,5,click,clack .. 2,3,4,5,click,clack etc.. pulled it into garage and it immediately stalled. did some reading and replace the Camshaft Positioning sensor. But now the car wont start.It cranks but wont turn over and start. It seems like its not getting fuel to system but the battery is also reading FAIL on my neighbors reader. Tried jumping it and it read 13.75V and when we would try to start it would drop to 11.5V... also It has been giving a "low flow EGR" code. I removed the EGR and cleaned it thouroughly, just haven't replaced becuase for some reason its $375 for my car.. PLZ SOMEONE HELP ME!! Im a corrections officer and drive 50miles to work and 50 miles home, this car is my life and I need it to feed my children and wife