The "real Mirage manual" describes a start-up with ground power available. As CrashO said, this is the normal way of starting-up the aircraft.
In this case, AC buses are then powered, and LP pumps work as soon as they're switched On.
If you start without ground power, only the start-up pump is powered (this one works on DC power, for this very reason). Read §1.3 in the RL manual.
At N = 45%, the engine turns quick enough for the alternators to come online. From that point onwards, you have full AC power (and working LP pumps).