As demand increases, less fuel is returned to the tank via the pressure regulator, more is sprayed into the intake manifold.
The pump is moving more-or-less the same amount of fuel at idle as at WFO/Max RPM.
Note that other vehicles may use a different fuel-supply strategy. A 2005 Ford Focus runs the fuel pump with a pulse-width-modulated voltage source, the pump works harder when the engine works harder. But that doesn't apply to GMT400s.
The pump is moving more-or-less the same amount of fuel at idle as at WFO/Max RPM.
Note that other vehicles may use a different fuel-supply strategy. A 2005 Ford Focus runs the fuel pump with a pulse-width-modulated voltage source, the pump works harder when the engine works harder. But that doesn't apply to GMT400s.
