I noticed the sample test question (in the book) regarding purging the fuel vapour from FI engine fuel lines.

I understand now after some googling that in some engines or perhaps I should say aircraft, that when the mixture is set for idle cutoff this opens a valve in the mixture spider and fuel is returned to the tank via a return valve.

Is this generally true of all engine installations or is it typical of continental engines only?

From what I have seen, mostly Lycoming powered aircraft none have had this purge feature.

Perhaps a few words in the text about this would be useful, if not for exam prep just for general information.

Doug