The fuel regulator has a tiny hole that's always open, along with the spring loaded regulator plunger. So when you turn the key on, fuel flows into the bowl, thru the open hole till pressure builds up to the point where the spring-loaded plunger starts to open. Then when the pump shuts off, the pressure HAS to bleed off completely thru the open pinhole. If it doesn't, something is plugging the hole. It may take a minute or two for the pressure to completely bleed off, but it definitely should NOT be pressurized after sitting overnight.