I just recently installed an auxiliary tank in my bed plumbed into the filler neck of the truck via an RDS gravity feed kit. I have an DeeZee vented fuel cap on one side of the tank, and a 1/2" npt rollover vent valve on the opposite side vented to atmosphere. The problem I'm having is the tank is building what I would think is too much internal pressure. I realize that the fuel will expand when its warm and build pressure in the tank and its not necessarily a bad thing but the last few times Ive taken the fill cap off the pressure is high enough that it will lift the cap and my hand off the tank about 6". I will say this tank isnt a mass produced name brand tank, it is a home made that I purchased from someone. It also doesnt seem to want to gravity feed any fuel when there is pressure in the tank which is odd to me because i figured the pressure would help push the fuel out of the drain on the bottom. Any insight and advice is welcomed, Im just about stumped on this one. Thanks in advance!