airbox spitter check valves. How to see if they are working

[RickB]

hey all,

Dallas made me aware of these check valves and my bus is spitting all over my car to the tune of a gallon or so after a full day of driving so if these are the culprits it would sure make my life easier. I know I will need to eventually address the core problem but for right now I'd like to check these first.
He instructed me to remove the check valves, my engine has two, clean them and blow through them.
This may sound silly but do any of you know if he meant blow through them with compressed air or literally blow through them using your mouth? (let's keep the laughter and comments to a dull roar here!  LOL).
Is the airbox pressurized? the reason I am asking is. When I use compressed air the valve works. When I try to blow through it. It doesn't work.  Any thoughts?
Thanks, Rick

[makemineatwostroke]

Rick; the check valve for DD works like this with the engine running at 900 rpm they are closed at idle they are open and one important thing the valve needs to be on a 45 degree angle if it is the right valve for the engine DD had some that would work on a 90 degree for transit engines. Start your engine if you are getting air from the valve at over 900 rpm take the valve apart and clean it or replace it         have a great day