RAM installation question

Question

Hi, I am upgrading a mid-2011 iMac from its original 4GB (2x2) of Ram to 16GB (4x4x4x4) of RAM. 
--After i replaced the old 4GB with the new 16GB, I attempted to start the computer and was greeted with the dreaded Beeping that so many of written about.
-- However, when I replaced the old 4GB with 8GB (4x4) and used the SAME PORTS that the old RAM had previously occupied, everything worked fine.
--BUT, when messing around to try to understand the problem, I experienced the Dreaded Beeping with the 8 GB configuration as well.
--Also, when I tried to start the computer with  new 8 GB RAM installed, but without the protective metal plate that covers the RAM ports, etc., the computer would not start at all.
Currently, the computer is running well on its new 8GB of RAM installed in the two ports previously occupied by the old RAM, with the outer plate re-attached.
So... the fact that my computer works with the new 8 GB of RAM, but has also not worked with the exact same 8 GB installed in the same ports leads me to hypothesize that possibly my problem is one of installation.  This hypothesis is further supported by the fact that I had a small amount of resistance re-installing the metal plate that covers the RAM ports after I installed the 8GB, and I had even more resistance when I had the 16GB installed (It bulged).
I would like to install the remaining 2 sticks of RAM into the two remaining ports and have 16GB of RAM, which is the maximum suggested by apple.
Is is possible that I am just not pushing forcefully enough when I install the RAM? 
Also, is it possible that the two ports that have been sitting unused need some sort of extra cleaning or lubrication?(i vacuumed out all visible fuzz, dust, etc.)?
I have watched a video on how to install the RAM, and am confident that I am doing so basically correctly.  Any help would be much appreciated.

Answer 1

It's very unlikely that RAM from Crucial was bad when delivered.  If, you purchased the correct RAM from Crucial, and you were careful and did not expose it to ESD when installing, and you fully inserted the RAM, then it should run great.
One easy way to determine if you have a bad stick at this point is to try two at a time in the slots that you know are working for you.  If those two work then try the other two.  If they work then all four sticks are fine.  If not, then use the process of elimination to determine the bad one.
If they all work, then either you are not seating them fully in the remaining slots, or, one or more of the other slots have a physical problem.  Try installing all of the RAM sticks again and then look at them all side by site.  They should all look uniformly inserted at the same level.  None should be bulging out on the ends or in the middle.  They should all look like they are fully seated.  In some cases it does take considerable force to fully seat a stick (the amount of force required is unfortunately relative and you will only be confident in the pressure that is required once you have done it on many machines).  Just make sure to brace you hands so you are applying pressure straight into the slot with your thumbs.