Have had the same issue going on for 3-4 months...there is a leak somewhere that is letting the fuel pull out of the front end of the system...I replaced, tightened, and troubleshot it all numerous times, and still not 100% sure I have it fixed, as my driveway slants and I just back in as a matter of habit now. I did just find very small seepage at the top of the IP, which is next on my list to repair.
It can be frustrating as hades but it's fixable...you didn't say what kind of vehicle this is?