Does it need to be energized to test vacuum or can I just bench test it with vac hose (properly clamped) and a mityvac? I have a few on hand and while all test correctly for resistance on the appropriate pins, I'm not able to get any vac with my mityvac. Am I missing something or are the diaphragms all toast?

if you can apply say 5 or so #'s of vacuum on the port & it doesnt hold (at all or drops to 0 in a period of time) its toast.

its that simple... if your mighty vac is working correctly... they must be all toast

I believe Paul Anders said 15Hg of vacuum?
but would have to go check to be sure
brant

Yes, 15 in Hg is the standard test, simulating idle vacuum on a stock engine. I've read a couple of specs about how much it can leak (e.g., < 5 in Hg in a minute, or < 5 in in FIVE minutes), but if it won't hold any vacuum it's done.

http://www.tangerineracing.com/mpsdiaphragm.htm

Here's Brad's page: https://members.rennlist.com/pbanders/manif...S%20Diagnostics

Double check you gauge and connections to make sure these are valid readings. Pull a vacuum on a vacuum cap first then work up from there.

15Hg=7psi approx

Got it. That's what I thought. I can pull vac with the mityvac on my skin, so I think it's fine.

Thanks.