@glum er 40-50psi with sufficient flow rate = every engine start.
I was thinking Airbus with no way of driving Hyds with APU apart from motoring the engines for five minutes before you blow the starter off the pad!! 50psi Accumulator pressure would be only px source.
Excuse my discrimination against Boeing. As previously said you could run Hyds from the ADP but what has caused your Total Engine Failure. Fuel??