Abstract: A two cycle crankcase compression fuel injected internal combustion engine has a first set of one or more throttle valves (104, 106) controlling combustion air flowing into the crankcase, and a second set of one or more throttle valves (110, 112) also controlling combustion air flowing into the crankcase. A throttle position sensor (104, 106) and controls fuel injection according to throttle position. Increased resolution of sensed throttle position at low engine speed is provided by admitting combustion air only through the first set of throttle valves (104, 106) and not through the second set of throttle valves (110, 112) at low engine speed for an initial given range of motion, such that greater movement of the first set of throttle valves (104, 106) is required to obtain a given amount of combustion air flow for a given engine speed, prior to opening the second set of throttle valves (110, 112), to provide more accurate fuel injection and better driveability.

Abstract: In a marine fuel system for a fuel injected internal combustion engine, a fitting (50) is provided in the vapor supply line (41). The fitting (50) has a first reduced diameter passage (57) providing a vacuum bleed orifice passage partially venting vacuum from the induction manifold (17) to atmosphere, to limit peak vacuum applied to the vapor separator (33) from the induction manifold (17). The fitting (50) has a second reduced diameter passage (56) providing a flow restrictor passage limiting the volume of flow of fuel vapor from the vapor separator (33) to the induction manifold (17). The fitting (50) limits fuel vapor supplied from the vapor separator (33) to the induction manifold (17) at peak vacuum from the induction manifold (17) during rapid engine deceleration to prevent an overly rich fuel air mixture in the induction manifold (17) otherwise causing rough idling or stalling. The fitting (50) also solves hot restart problems.

Abstract: A marine fuel injection system for a two cycle crankcase compression internal combustion engine includes a puddled fuel return line (44) between the crankcase (16) and a vapor separator (33). A shut-off valve (50) in the puddled fuel return line (44) is closed at high engine speed to prevent the flow at a high rate of a substantially gaseous medium to the vapor separator, to prevent fuel foaming otherwise caused thereby in the vapor separator and which would pass through the vapor vent line (41) to the induction manifold (17), causing an over-rich condition at high engine speed. At low engine speed, the shut-off valve (50) is open, permitting flow of puddled fuel to the vapor separator, which flow is substantially more liquidic and at a lower rate.

Abstract: A fuel injection system is provided with a purging device (14) for purging gas, including air and vapor, from the system. The device includes a pressure responsive valve (22) permitting gas to flow from an inlet (16) connected to the high pressure fuel injection line (8) to a vent outlet (18), and blocking flow when gas has been purged from the system and fuel pressure rises. A first branch passage (24) communicates between the inlet (16) and one side (26) of the valve (22), and a second branch passage (28) communicates between the inlet (16) and the other side (30) of the valve (22) and also with the outlet (18). A restriction orifice (34) in the second branch passage (28) provides a fuel pressure drop thereacross but does not substantially drop gas pressure thereacross, such that pressurized fuel causes a higher pressure on the one side (26) of the valve (22) than on the other side (30) of the valve ( 22), which pressure differential closes the valve.

Abstract: In a two cycle internal combustion engine (2), a fuel injection system is provided with a low profile compact intake manifold (22) mounted to the crankcase (8) by an adaptor plate (24) and defining an intake air flow path in a first direction (28) behind the manifold (22) through a gap between the manifold (22) and the crankcase (8) provided by the adaptor plate (24). Intake air then flows (32) into throttle bore passages (30) from behind the manifold and then reverses direction and flows through supply passages (34) having fuel injectors (38) and then into the crankcase (8). The passages share a common plenum (42) within the manifold. The fuel injectors (38), their electrical connectors (48) and a common rigid fuel supply rail (44) are all in the common plenum (42) entirely within the low profile manifold (22) and sealed from moisture and salt in a marine environment.

Abstract: A marine fuel supply system for a fuel injected engine (10) deadheads a high pressure fuel line (27) with a closed-end connection to the fuel injectors (24) without a recirculating return fuel line to the fuel injection pump (25) and without a return fuel line to the remote fuel tank (29). A differential pressure transducer (33) senses differential pressure across the fuel injector (24) between the high pressure fuel line (27) and the low pressure induction manifold (17) and turns off the fuel pump (25) above a first value of relative differential pressure and turns on fuel pump (25) at a second value below the first value, to maintain the fuel pressure in the high pressure line (27) within a given range relative to induction manifold pressure.