Bi-fuel engine

A bi-fuel engine that can selectively use one of gas fuel and liquid fuel, comprising:

• a gas fuel supply passage connecting a gas fuel source with an intake system;
• a liquid fuel supply passage connecting a liquid fuel source with the intake system;
• a pressure supply passage extending from a pressure source of the engine, and branching into a first branch passage and a second branch passage at a branching portion;
• a gas fuel on/off valve provided in the gas fuel supply passage and connected to the first branch passage so that the gas fuel supply passage may be opened when pressure is supplied to the gas fuel supply passage, and may be closed when pressure is not supplied to the gas fuel supply passage;
• a liquid fuel pump provided in the liquid fuel supply passage and configured to feed the liquid fuel under pressure to the intake system by a pulsating pressure supplied via the second branch passage;
• and
• a switch valve provided in the branching portion to switch between the first branch passage and the second branch passage for conducting pressure supplied from the pressure source via the pressure supply passage.