I'm reading some paper tutorials on the OBD-II EVAP system. These particularly have to do with the "early" and "late" systems on Toyotas, but I think my questions may be fairly generic to all systems.
There are several electric solenoid valves in the system: Canister Closed Valve; Purge Valve; Bypass Valve. Some systems have a Vapor Pressure Sensor 3-way Valve instead of the Bypass Valve.
There is a non-electric Air Drain Valve. This allows exhaustion to the atmosphere of excess tank pressure (after it has passed thru the canister). The tutorial shows the Drain Valve ONLY functioning when the gas tank is being refilled with fuel.
My questions:
1) With the ignition key OFF, what is the default state of the electric solenoid valves? Are they CLOSED or OPEN?2) Does the Air Drain Valve relieve tank pressure at any time other than during refuelling?