This invention relates to a fuel supplying device for a marine propulsion engine and more particularly to an improved arrangement for enriching the fuel supply to an engine under certain running conditions.
It is well known in the charge forming systems for internal combustion engines to provide supplemental fuel supply for accommodating certain running conditions. Such supplemental systems are frequently employed in connection with charge forming systems employing carburetors. The reason for this is that the normal charge forming system may not be able to accommodate all of the various fuel/air supply requirements for an engine as are encountered during its running and operation. For example, it is usually desirable or necessary to provide supplemental fuel for starting, particularly at low temperatures and also for warm up operation under low temperature conditions.
One highly effective form of supplemental fuel supply draws fuel from the fuel bowl of a carburetor, for example, one carburetor of a multiple carbureted engine, and supplies this supplemental fuel to a number of cylinders through a spacer positioned between the carburetors and the intake manifold. With such systems, it is also desireable to provide supplemental air for running under these conditions to insure better combustion.
This supplemental air may either be drawn from an atmospheric source directly or from the area over the fuel in the fuel bowl of the carburetor from which the fuel is drawn. If the latter arrangement is employed, certain problems result. That is, if supplemental air is drawn from the area above the fuel in the fuel bowl, then a reduced air pressure acting on the fuel in this fuel bowl will cause a decrease in fuel supply through the main circuits of the carburetor such as the idle or main discharge circuit. As a result, the amount of supplemental fuel introduced to the spacer may increase but the total fuel supplied might either stay the same or be decreased. These problems are particularly acute when operating an idle due to the low suction which exist at the idle discharge ports and the flow restriction in them. In addition, when the system is utilized with an outboard motor which may be tilted to various running conditions, the combination of the reduced suction and the trim angle can serious deplete the fuel supply and cause uneven running or even stalling under extreme conditions.
It is, therefore, a principal object to this invention to provide an improved fuel supplying device for a marine propulsion engine.
It is a further object to this invention to provide a fuel supplying device for a marine propulsion engine wherein both air and fuel are supplied and the supplemental supply is operated in such a way so as to increase the amount of fuel supplied by the main fuel supply system as well.