I've changed quite a few fuel filters and have had no problems but today, me and my friend were changing the fuel filter on his 96 GT, he let one of our other friends change it about 4 months ago. So i go ahead and pull the clamps out and pull the (out) line off first, since he was on the other side i told him pull out the (in) side, we get the old filter off and put the new one on. I put the (out) line on and then he put the (in) line on. he was pressed the gas down and tried to start it, wouldnt start the first or second try but it started up the third time then we noticed it was leak fuel, we took it off and put it back on same results, we were trying for over 2 hours and kept comin up short handed, does anyone have any idea what could be going on, because the filter seems to be fitting snug on the (out) line but not on the (in) line

 

Sounds like it's not snapping into place. Like the lock ring is jacked up.