A. a pressure regulator can become defective due to foreign material or a ruined diaphragm.
B. high pressure is usually caused by a bad pressure regulator or on looped systems when a pressure return line to the fuel tank is kinked.
C. if gasoline drips from the vacuum hose when it is removed from a fuel pressure regulator, it is defective.
D. fuel pressure regulators usually fail by causing pressure that is too high rather than too low.