My dad's truck (2000 7.3) has a fuel leak on the passenger side rear of engine. Replaced hard line to back of head (had a hole worn in it), still leaks. Removed check valve and re-taped it and new o-ring on hard line. Leak slowed but still there. I used Ford parts for this and am wondering if there is something different or I am missing, these seals seemed kinda hard. It also only seems to leak when the truck is running and hot, can run fuel pump by itself and no leak. I'm at my whit's end please help!