2000 Chrysler Sebring cant start it

So I got a sebring lxi. Been sitting for a little over a year.I had it starting up there for awhile and then one day it wouldnt start.I have pretty much done a tune up on the car while its been sitting.I had a mobile mechanic come look at it. He hooked up his computer and didnt get back any codes probally because the car wasnt running. He checked my feul pressure and found out that I only had about 10psi when it should be 50psi.I got an old one off a 96 dodge avenger. Put it in and I can hear it pumping and everything but still no start. The car just cranks and cranks but wont turnover. What would be the next best geuss of what it could be.I heard that sometimes the alarm system can affect the starting of my particular vehicle. Any ideas is greatly appreciated.