markmast has a good answer - I’ll add this simple bit here… On most fuel injected engines (ok, every last one I’m familiar with), the throttle is either electronic, in which case pumping prior to turning the car on does nothing as the circuit is dead, or the throttle is connected via a cable just to the throttle body. When you step on the gas, all you’re doing is opening and closing the throttle plate, which is simply regulating air flow, not fuel flow. Fuel flow is controlled by the computer, which uses a throttle position sensor along with other sensors to determine how much gas to add. When the car is off, that circuit is dead, so the only thing that happens by pumping the gas is that you’re moving that butterfly valve in the throttle body… nothing else…