Abstract: An automatic fuel enrichment system for cranking and warm-up of an internal combustion engine in which a solenoid valve is responsive to control electronics for selectively feeding enrichment fuel to the engine air intake manifold. The valve control electronics receives a signal from the engine ignition system and controls a solenoid valve as a function of engine speed. Specifically, the control electronics energizes the solenoid valve when engine speed exceeds a preset minimum cranking threshold until the engine reaches a preset idle speed threshold, at which point enrichment is terminated. In the event that the engine begins to stall during warm-up and engine speed declines to a preset intermediate threshold, the enrichment valve is again energized until the engine reaches idle speed.

Abstract: A carburetor for an internal combustion engine is provided with auxiliary fuel means for continuously regulating the fuel air ratio from a first, cold start condition to a second, normal run condition. The auxiliary fuel means includes a vacuum operated metering system to provide the additional fuel required for starting and running the engine untile the engine reaches normal operating temperature, and a combination shut-off valve and air bleed. In the preferred embodiment, the air bleed is actuated by manifold pressure overcoming the closing force of a thermostatic coil, and is open whenever the engine starts. The air bleed increases air input to the auxiliary fuel supply, thereby reducing fuel richness after start. A temperature sensitive element such as a bimetal coil is utilized to operate the shut-off valve and completely closes the auxiliary fuel means input to the engine at some predetermined temperature.