Fuel pressure check and fuel filter location

Thanks, feel like i am back at square one. Problem is when fueling up the car will not start, it turns over but you must wait a few munites before it starts. Could this be a faulty gas cap not allowing the system to pressure up? Would it be worth pulling fuel pump? I did pull rear seat and have axcess to top of gas tank. I do see the fuel pump but there also some other unit going into the tank with a wire harness any idea what this is? Thanks for youe help