Abstract: A control device calculates an estimate of negative intake pressure based on the relationship between the rotation speed of a crankshaft and a throttle opening degree (Step S24). Then, the control device sets the estimate PE of the negative intake pressure, which is calculated in Step S24, to a greater value as combustion efficiency of CNG used in engine operation becomes higher (Step S25). When the corrected estimate PE of the negative intake pressure becomes smaller than or equal to a reference value PTh (Step S26: YES), the control device starts a negative pressure recovery procedure (Step S27).

Abstract: A control device calculates an estimate of negative intake pressure based on the relationship between the rotation speed of a crankshaft and a throttle opening degree (Step S24). Then, the control device sets the estimate PE of the negative intake pressure, which is calculated in Step S24, to a greater value as combustion efficiency of CNG used in engine operation becomes higher (Step S25). When the corrected estimate PE of the negative intake pressure becomes smaller than or equal to a reference value PTh (Step S26: YES), the control device starts a negative pressure recovery procedure (Step S27).

Abstract: A fuel supply apparatus is constructed such that an engine fuel to be supplied by injection to an internal combustion engine can be selectively switched to a first fuel or a second fuel. The fuel supply apparatus is equipped with a control unit that performs air-fuel ratio learning related to the injection amount of the engine fuel such that the actual air-fuel ratio detected by an air-fuel ratio sensor installed in the internal combustion engine agrees with a target air-fuel ratio. During the operation with the first fuel, the control device permits the switching of the engine fuel from the first fuel to the second fuel after a condition that includes the completion of the air-fuel ratio learning related to the first fuel is met.

Abstract: A fuel supply device includes: a fuel tank; a fuel supply path through which fuel stored in the fuel tank is supplied; an electric-operated cutoff valve located in the fuel supply path and opened in response to conduction through the cut-off valve; and a controller that controls conduction through the cutoff valve. The controller opens the cutoff valve by conducting an open driving current through the cutoff valve. The open driving current is larger than a holding current of holding the cutoff valve in an open state. Based on a conduction history of the open driving current through the cutoff valve within a retroactive period, the controller implements a process of prohibiting conduction through the cutoff valve.