In at least some implementations a carburetor may include a main bore through which a fuel and air mixture is delivered from the carburetor, a fuel metering assembly, a supplemental fuel pump and a valve. The supplemental fuel pump includes a diaphragm that defines a fuel chamber on one side from which fuel may be discharged to at least temporarily increase the amount of fuel discharged from the carburetor and a reference chamber on the other side that is communicated with a reference pressure source. The valve is electrically actuated and moveable between first and second positions to at least substantially prevent communication of the reference pressure source with the supplemental fuel pump diaphragm when the valve is in its second position to thereby inhibit or prevent fuel being discharged from the fuel chamber.