Methods and systems for shut down of a multi-fuel engine

A method for an engine comprising:

• determine an operating condition of the engine as being at least one of a first condition or a second condition;
• venting each of a first fuel line portion coupling a fuel reservoir to a vaporizer unit and a second fuel line portion joining the vaporizer unit to the engine until both fuel lines are depressurized during the first condition, and
• venting and depressurizing the second fuel line portion during the second condition, wherein the engine is adapted for combustion of more than one type of fuel and the more than one type of fuel comprises hydrogen, each of the more than one type of fuel comprises a source or reservoir, and venting comprises suspending flow of hydrogen from the source or reservoir of hydrogen and removing hydrogen from at least the second fuel line joining the engine and the vaporizer unit so as to reduce contact of hydrogen with components of the engine.

A system for a dual-fuel engine in a vehicle, comprising:

• a controller storing instructions in non-transitory memory that, when executed, cause the controller to:
• in response to a request to suspend fueling engine cylinders with hydrogen,
• rotate the engine one or more times, unfueled, to route hydrogen from a fuel line to an exhaust stack, wherein the engine is adapted for combustion of more than one type of fuel and the more than one type of fuel comprises hydrogen, each of the more than one type of fuel comprises a source or reservoir, rotating the engine one or more times, unfueled, to route hydrogen from the fuel line to the exhaust stack comprises suspending flow of hydrogen from the source or reservoir of hydrogen and removing hydrogen from at least a portion of the fuel line joining the engine and a vaporizer unit so as to reduce contact of hydrogen with components of the engine.