1988 ranger smog air bypass valve?

My uncle's 88 ranger has a 2.0 and is hard to start. I thought that the auto choke needed replacing... however I am not so sure as we can't seem to find parts for the carb anyway..... He can spray starting fluid in the carb and it starts fine, but has to let it warm up for it run smooth... without starting fluid, he has to start it several times in order to get it warmed up enough to go on his merry way. I looked at it for him and found that the choke portion of the carb has a blue vaccume line coming in on the drivers side. I pulled it off and noticed it didn't have a vaccume on it. Does it suppose to? I traced it back to the air bypass valve on the smog pump. No vaccume there as well. I would really like to know how this valve is suppose to work. It is around 100 bucks and I would like to know a little about it before going any further. I think this is the problem however I just don't know that much about this area....
Thanks for any info that may help me understand the valve.