I have pulled a bunch of the door actuators in the yards. 9 out of 10 are usually good. I don`t take a Mity vac with me, I pop off the door panel, remove 2 8mm screws, pull off the 2 vac lines and pop off the rod.
Suck on either one of the 2 vac lines and if they hold vac will, hold your tungue to it.
I took one apart to see how the innerds were put together. seems like the 2 halves were just snapped together and I pryed them apart. (Don`t have one in front of me at the moment) the rectangle diaphram had a small crack from years of use and heat etc...
the rubber piece the rod goes through at the top doesn`t seem to be replaceable because of the way the plastic piece the rod snaps into if fixed to it. don`t think it can be taken apart to be reused to work.
usually what I have seen is the rubber cracks at the rod.
Chad, this is a good tip and if they work for the trunk and fuel door, this is a good cheap DIY repair.
Charlie