text:  a regulator is installed next to the carburetor where the fuel line goes in, and it returns everything it doesn't need back to the tank. So it's always circulating the fuel in that line, pulling out the fuel from the tank, dumping it back, keeping the line a little cooler. But the pressure is what keeps a modern car from going into vapor lock. If there's no pressure, the fuel will boil off at a certain temperature.