Throughout this site we use many technical terms, and given the breadth of readership our site enjoys, sometimes we are remiss and incorrectly assume everyone knows what we are referring to. For those that do not, here are some explanations of the technical terms use.
A pump in the carburettor which enriches the fuel/ air mixture as the accelerator is depressed. It is either piston- or diaphragm-operated. Attached to the carburettor body, it performs the specific function of negating the lean-out effect caused by sudden large throttle openings. It is activated directly off the throttle cable (or linkage) via a diaphragm arrangement and nozzle. Sudden throttle openings activate the diaphragm which forces petrol through the nozzle into the carburettor throat. On slow throttle openings, there is a bleed-by arrangement that allows the fuel to return to the pump bowl rahter than being forced through the nozzle.