"Ken Grunke" wrote in message
...

I am assuming there has to be a separate check valve INLINE between the
plug adapter and the gauge below the release valve. That is what I am
missing. It may be a fitting I had, but absent-mindedly misplaced.

Could be a spring and or check ball is missng or gunked up at the spark plug
fitting end...

--FWIW blowing into the end with your mouth probably won't produce enough
hose expansion to actuate a ball type check valve.