In at least some implementations, a carburetor includes a body, a fuel pump diaphragm and a pressure pulse passage. The fuel pump diaphragm is carried by the body and defines in part a fuel chamber on one side of the fuel pump diaphragm and a pressure pulse chamber on the other side of the fuel pump diaphragm. The pressure pulse passage communicates the pressure pulse chamber with a pressure pulse source to provide pressure pulses in the pressure pulse chamber to actuate the fuel pump diaphragm. The pressure pulse passage includes an inlet communicating with a passage in which pressure pulses are present and the inlet is spaced from a surface defining the passage in which pressure pulses are present.

A carburetor provides a supplemental fuel supply to an engine and includes a body, a fuel metering diaphragm and a fluid pump. The fuel metering diaphragm defines part of a fuel metering chamber and a reference chamber and has at least a portion that is movable relative to the body to increase and decrease the volume of the fuel metering chamber to control fuel flow in the fuel metering chamber. The fluid pump is carried by the carburetor or another component upstream of the carburetor and has an outlet in fluid communication with the metering reference chamber and an actuator arranged to discharge fluid through the outlet to increase the pressure within the metering reference chamber and thereby increase the fuel flow rate from the fuel metering chamber to the air-fuel passage to provide a supplemental fuel supply to the engine.

A carburetor provides a supplemental fuel supply to an engine and includes a body, a fuel metering diaphragm and a fluid pump. The fuel metering diaphragm defines part of a fuel metering chamber and a reference chamber and has at least a portion that is movable relative to the body to increase and decrease the volume of the fuel metering chamber to control fuel flow in the fuel metering chamber. The fluid pump is carried by the carburetor or another component upstream of the carburetor and has an outlet in fluid communication with the metering reference chamber and an actuator arranged to discharge fluid through the outlet to increase the pressure within the metering reference chamber and thereby increase the fuel flow rate from the fuel metering chamber to the air-fuel passage to provide a supplemental fuel supply to the engine.

A carburetor including a body having a main bore through which a fuel and air mixture is discharged from the carburetor for use by an engine a priming passage communicated with the main bore, a pump that moves fluid into the priming passage, and a flow restrictor received within at least a portion of the priming passage to reduce the minimum effective flow area of the priming passage. The flow restrictor has a body received at least partially within the priming passage so that fluid flows around the flow restrictor and between the structure defining the priming passage and the flow restrictor.

A carburetor including a body having a main bore through which a fuel and air mixture is discharged from the carburetor for use by an engine a priming passage communicated with the main bore, a pump that moves fluid into the priming passage, and a flow restrictor received within at least a portion of the priming passage to reduce the minimum effective flow area of the priming passage. The flow restrictor has a body received at least partially within the priming passage so that fluid flows around the flow restrictor and between the structure defining the priming passage and the flow restrictor.

A carburetor has a carburetor body having a venturi passage that conveys air from an air inlet to an air outlet. A throttle valve controls flow of the air in the venturi passage. The throttle valve is movable into a closed position, an open position, and at least one transition position between the closed position and the open position. A fuel bowl holds fuel for mixing with the air in the venturi passage. A main nozzle discharges the fuel from the fuel bowl to the air in the venturi passage when the throttle is in the open position. A secondary circuit that is smaller than the main nozzle discharges fuel from the fuel bowl to the air in the venturi passage when the throttle is in the closed position, the transition position, and the open position. A filter is configured to remove particulate matter from the fuel in the fuel howl prior to discharge via the secondary circuit. Methods are for making the carburetor and operating the carburetor.