It's all in the GM/Cadillac service manuals - a www.alldatadiy.com
online service. Or, you could Google "cadillac forums northstar evap system" or something close.
You're confusing the EVAP system with part of the cooling system. EVAP stores fuel tank vapor for later burning, then sends it to the intake manifold by opening a purge valve on the throttlebody and opening a fresh air vent at the charcoal canister - the resulting vacuum then moves fresh air through the charcoal canister to move the vapor into the intake manifold for mixing with the air/fuel charge. EVAP operates at steady speeds over 30 mph.
A clogged EVAP canister vent solenoid line will cause premature fuel pump shutoff - not at all common in our cars
. Common in Escalades because the charcoal canister isolation screens break and the pressure/vent/suction/vent action moves charcoal granules throughout the system.
You need to get into the service manuals to find out how all this stuff works ......... "it's in the book" !
Our fuel fill pipes have flow restrictors in them - mainly to prevent siphoning fuel from the tank - it's either a small orifice or a fine screen. High fuel pump flow can trip the auto shutoff. Our fill pipes also have an internal vent pipe that runs from the tank top top the upper end of the filler pipe - inside the pipe, after the cap. Look at the pictures in RockAuto, INFO tabs.