I reached the limit for attachments on the previous post so had to make a second post to include a couple more pictures that may help. These pix are of a similar mechanism (tag reads C0AE... so presumably for a 1960 Ford). The concept is the same - the vacuum motor pulls up on the arm which also mover the pump drive wheel over to contact the generator drive belt causing the pump wheel to turn. Although the concept is simple, the design didn't produce a durable pump. The impeller siezes quite easily. However, the power applied to the pump wheel causes it to turn no matter what, so the impeller breaks loose from the pump drive shaft - and the pump is shot. That is unless you have a similar spare pump, in which case you can cannibalize the spare pump for parts to make the original one work again - which is why I have a spare pump.
"Old Betsy" - my '59 convertible J9YJ116209 Thunderbird Registry #33341