Originally Posted by davekippen
Even with it all the way compressed it still is too long. It will not compress far enough to where I can get the threaded ring to contact the tank threads.
It won't contact the tank threads because you have the tank sitting on the dimple on the bottom of the tank. Remove the tank from the skid and set the ends on 2x4's to let the middle of the tank sag.
As far as any other dimensional differences, that's due to your replacement tank being stored without a pump in it out in the air and as it dried out, it shrunk a bit. The plastic swells and changes shape and size a lot when it's full of fuel.
It's a very common misconception that the spring loaded part of the fuel pump assembly is there to allow the bottom of the tank to be pushed up without moving the pump up against the lockring. What is overlooked is the fully compressed height of the fuel pump assembly is
the height of the tank. There is no room for it to compress when it's installed.
Also, your replacement tank may have been stored with something sitting on top of it which has caused the top to sag a bit.
Just prop the ends up and the pump will go right in.