1 - How does the OEM fuel pump know when the system is pressurized?
I assume there is some kind of sensor in the pump or the priming process is only based on a certain amount of time the pump stays on before it stops the priming process.
If there is some kind of sensor, then question 2 applies
2 - With a surge tank fitted, how does this sensor register a pressure? As the fuel is being pumped into the surge tank, which has an outlet that allows the fuel to flow directly back to the tank.