75 dc pump used for starting the apu and once up to speed l ac pump auto switches on and the dc pump switches off.
The dc pump on a 73 is an option believe it or not and the apu does not need a pump in the tank to start.Some 73/300's I work on at present don't even have a dc pump amd quite a few of the 200's didn't either.
APU's will suction feed due to a small pump in the fuel control unit.
------------------
So that you may not be the martyred slaves of Time,
get drunk, get drunk,
and never pause for rest!
With wine, poetry, or vitrtue,
as you choose!"