From Vol B 24-35-8 Electric Fuel Pump - Diagnosis: “ It is only necessary to test low-pressure pumps if noise or very low flow is a problem with a two pump systems.” 5.0 EFI pressure ENG ON 30-45psi, Key ON Eng OFF 35-45 psi.
24-35-11 It has been observed that if the low pressure pump is running, it is almost certain that is operation correctly. Therefore, flow testing the fuel pump is only necessary if there is good reason to suspect pump damage which would cause the pump to “run but not pump.”
C1 Flow Test:
Remove ground from test lead
Disconnect pressure line from pump at reservoir
Obtain Calibrated container of at least one quart capacity
Place fuel line removed from reservoir into container
Ground test lead and run pump for 5 seconds
Is fuel level at least ounce (180ml)
I found some areas that mentioned pressure between 3-5 psi. But sounds like if your high pressure pump is good but not giving pressure, and you check your low pressure pump you should be more concerned with fuel flow rate vice fuel pressure.