2002 Dodge Caravan FUEL LINES

I'm experiencing a problem with the fuel going to the injectors on a 2002 Dodge Caravan 3.3 L. I've put in a new pump and filter, but no gas will push through. I've disconnected the lines before the fuel filter and back flush. Air goes through just fine blowing back from the engine, but no air comes through when I apply air pressure from the rear after the air filter. Is there a check valve somewhere in there that's being regulated by the ASD relay? I don't see any attached. Thanks