currently going through trouble shooting process for 4x4 not engaging, found the actuator,now exactly what i'm I looking for to see if its in working condition?

 

Talking about the one on the fender by the battery right?
If so, take the vacuum hose off, push the rubber diafram in with your fingers and put your thumb over the vacuum hose hole. IF the diaframe stays put its fine, if it moves you ahve a leak and it needs to be replaced.