Secondary air pump code troubleshooting - valve, pump or both failing?

[bond007]

Trying to troubleshoot a persistent P1423 code...

Things checked:
* SAP operates upon startup and "reasonable" airflow is felt at the feed tube for the exhaust valve
* Exhaust valve seems to flow air only in one direction (can blow but not suck through the air pump side)

Observations/potential causes for the code:
1) Not all rivets are in place in the SAP. Does the SAP have reduced airflow if not all rivets are in place? If so, I guess I will be removing it, drilling the remaining rivets, inspect it while I am at it and replacing with hardware.

2) I put a vacuum gauge inline to vacuum line that is fed by the solenoid and found that some engine vacuum is present when the system operates but it is reduced (5" Hg) from the normal engine vacuum found at the manifold (20" Hg).

Can anyone tell me if this is normal or if you should see full engine vacuum at that port with the valve hooked up? I don't see why you would not from my previous encounters with electric-pneumatic systems (reference, "rat's nest" of 3rd generation RX-7). My next test will be to look at the vacuum without the valve connected.

My guess from this diagnostic info is that there is a leak in the vacuum line somewhere from the fitting on the intake manifold up to the air valve. #3 seems to point to the valve itself.

3) I connected a mityVac to the valve and it seemed to have trouble maintaining vacuum to keep it open. I had to continue to pump the mityVac to open the valve to flow air through the air port and was blowing air through the port with my mouth to verify airflow. Prior experience with these systems would point to a diaphragm failure in the valve preventing vacuum from being maintained.

Any thoughts/comments would be appreciated.