For Info.
I believe that the B777 fuel system has a suction feed system from tanks so that in the event of a.c fuel pump failure (of anykind),the engines will still receive a flow of fuel via suction ,albeit at a slightly reduced rate.
Suction Feed
-Suction feed line bypasses pumps.
-During climb air from fuel tank may collect in suction
feed line, inhibiting suction feed. Air will deplete
eventually after reaching cruise.
-Once air dissolved suction feed can occur with no
limitation.
-Time to deplete depends on altitude, fuel temp and
type of fuel.