OK I'm having a puzzling problem with my (new) old hot tub.

I though is was just a missing o-ring on the diverter jet (american products) so that was replaced.

I cut the flow off to the jets and everything works fine. The water flows out of the large diverter jet, and I can adjust the amount of air drawn into the jet.

Now I turn the diverter the other way and water flows to all the jets, but no air gets pulled in. The air control knob is working, (twist open twist closed). The air manifold is full of water and slightly pressurized.

I'm at a loss here....

I'm going to pull all the jets and hope I find a missing seal at the back of one of the jets.

Any suggestions?

Yep.
Suggestion is to follow your specific course of action. A bad seal in the back of any jet will cause this problem.

Thanks,

All the rear seals look good, it may be an internal jet seal.

Mike

A missing insert can cause this problem as well. Many older tubs have an insert that you can adjust to direct the water flow. If you don't have these, the jet may not be able to make the venturi action to draw in the air.