AnFI(really!)'
Where does the fuel pressure warning come into your theory?
Your swimming pool emptying with a straw as opposed to a thimble 'parallel' has no relevance, as the transfer pumps are at the bottom of the 'pool', so the transfer system is more like a bath plug than a straw! Likewise for the supply, as when the fuel pressure caption comes on you switch on the prime pump!
Thank you Arkroyal, would that be sufficient fuel in the supply tanks or the main?