Quote:
The high stage valve is closed during engine start.(737NG).
As I say, my reference is to the original arrangement with the -100/200 PW-JT8 powered 737.
There's a very old sketch here from a website discussing the 727 about 3/4 down the page. The bleed valve is not shown but clearly it would have to be open for engine start to allow air flow to the starter.
Hope this clarifies my point.
The high stage valve is closed during start(9th stage),and the Pressure regulator shutoff valve is ALSO closed when either the bleed is in OFF position or engine start valve is in OPEN position,and othe r reasons such as over pressure or temp...