2000 XJ 4.0...Woke up this morning to go to work..turn the key and it would just crank..engine wouldn't turn over. Kept doing it..then i tried to put my foot on the gas to give it some help, That works as long as i keep my foot on the gas, once i remove it, it stalls. Any ideas? I was thinking fuel filter or pump on th way out. I don't know where to start