[DesertMK4]

The Holley pump works off a cam on the driver side of the carb. This cam pushes down on a lever. The lever then pushes the diaphragm on the pump. The pump then sends an extra gas squirt into the throttle bore. This is intended to smooth the transition as throttle is opened by enriching the mix. The pump only works when the throttle is opened more. A spring on the diaphragm returns it and draws more gas into the pump. You get no pump action at a steady state of throttle. Holley has videos on adjusting the pump, lever, cam and squirt nozzles.