I have been working on my cruise off and on for some time and if anyone could tell me the connections to the Vacuum pump. The connection next to fender has one cap and one is open. The one to the left has the connection to the diaphragm and to the pedals, the other is open. Should this have a check valve on it?
Every thing in the Bentley passes and if I cap the open connection on the left the cruise works but you can release it.

Thanks in advance
1986 1.6TD