Here's what I've understood for fuel injected cars.
The fuel system is to "hold" fuel pressure so that the next time you start it you can crank it right away, and you will have pressure at the injectors even though the fuel pump is just getting started.
However, the longer the car sits the more the residual fuel pressure goes away. Therefore it becomes increasingly important to get the fuel pump running to pressurize the system while there is no load on the battery cranking the vehicle.
When you first turn the key to "ON", not the whole way to "START", the fuel pump will run to pressurize the system for about 2-3 seconds, then shut off. Any excess fuel pressure is sent back to the fuel tank by way of the pressure regulator and a return line. On Hondas, you can hear the electric fuel pump start and stop. The engine does not need to be running.
Therefore, in a fuel injected vehicle it's a good habit to pause for 1-2 seconds when starting the car to let the fuel pump pressurize the system.
[ January 29, 2004, 08:20 AM: Message edited by: S2000driver ]