You may, if you're not already a member, consider joining the Registry. I say that because over at our ZR1NetRegistry web site the latest newsletter, "Heart of the Beast", has a Tech write up by Marc Haibeck explaining the operation of the secondary port throttle system mechanically and from a vacuum requirement view point. I found the article to be most revealing and easy to follow. You could do your own trouble shooting of the system from the info in Marc's article. Kudos to DDSLT5 and Marc (the man) for a great newsletter!
Anyway, if you turn the key to "on" and go listen by the pump you should hear it cycle to charge up the system and then every so often it may re-cycle for a couple of seconds. If you don't hear it at all then unplug the vac line that goes from the pump to the hose that goes under the plenum. Over at the right water tube @ the I/H near the alternator you will find that coupler. If you unplug at that spot and the key is on the pump should run & if you cover the end from the pump the pump should stop. You can also put your mighty vac pump there to test some of what is under the plenum...not all of it but if the vac gauge drops like a rock then you may have a problem with: Actuators, or control solenoid, or check valve, or the Tank, or any of the connection points in the secondary vacuum spider. To do this basic preliminary test you only need to put about 10" of vac on the line going under the plenum & see what happens. If when testing that line, you get it to hold vacuum then the solenoil will need to be activated to then test the actuators. You can see them thru the gaps in the runners with a flashlight. That's what learned from Marc's article. I can go re-read it and give you the proceedure if you need it.
Tom