here is my average diagram
http://www.iforce.co.nz/View.aspx?i=apuhwgoi.jpg
when you start cranking the engine over, 12v is taken from the starter to open the relay, so the 12v from ignition or where ever you took 12v from can flow through the open circuit relay to the fuel pump, once the engine has enough air flow (engine running) the air flow meter acts as a earth for the open circuit relay and allows current to flow from the 12v source to keep the open circuit relay latched and allow power to flow to fuel pump allowing it to well pump
also 12v is taken from the starter to the ECU.
p.s the ECU does not actually control the fuel pump, the airflow meter does, it's simply on or off.