Start-up of an internal combustion engine comprises maintaining one or more engine valves in an engine cylinder in a continuously open state for more than one engine cycle during engine cranking. When it is determined that an engine parameter or transmission oil pressure has reached a predetermined value, maintenance of the one or more engine valves in the continuously open state is discontinued and fuel is subsequently provided to the engine cylinder for engine start-up. In various embodiments, the engine parameter may comprise an engine temperature parameter, an engine pressure parameter or an engine electrical parameter.

A latch assembly and valvetrain therewith can comprise a stationary housing comprising a plunger cavity, a plunger in the plunger cavity, and a controllable upper latch member. The plunger can comprise a control end, a plunger body, a spigot body and a spigot end. The controllable upper latch member can be configured to selectively act on the control end and can be configured to switch between locking the plunger from moving along a first axis and unlocking the plunger to slide in the plunger cavity along the first axis. A slidable transverse latch member or rotatable upper castellation body can act as the controllable upper latch member. While a valve bridge and rocker arm can be movable, the housing for the latch assembly can be stationary.

A decompression device for an internal combustion engine comprises a valve rocker shaft bracket and a valve rod. A valve spring is sleeved on the valve rod, and above the valve rod a valve rocker is arranged. The valve rocker shaft bracket is connected to a decompression bracket. The valve rocker is movably connected to a valve opening/closing device connected with a control device. When the internal combustion engine is started, the valve opening/closing device receives a control command from the control device to keep connecting with the valve rocker for a time, and then disconnect, so that the valve rod arrives at the valve closing position.