thanks for the replies and info.

I checked all the connections to the canister then dissasembled the valve, hoses and filter. I blew out the filter with compressed air [some black soot came out but not a lot and I doubt it would have been enough to impede the vacuum. I reassembled and will see what happens. I'd like to check the pipe all the way back to the tank but it is just too hot to spend that much time under the car for a "minor" issue like this.