Methods and systems are provided for varying fuel injection pressure in a gaseous-fueled vehicle. A mechanical pressure regulator may be modified to regulate the pressure of gaseous fuel to varying pressures based on electronic pressure feedback and engine operating conditions. In one example, a regulating pressure in a low pressure chamber of a pressure regulator may be varied by controllably flowing gaseous fuel into or out of a reference chamber of the pressure regulator, and the gaseous fuel exhausted from the reference chamber may be directed to the engine for combustion.