fuel gauge not working

so i had a t100 tank and the fuel guage worked...just swapped in a tacoma tank...wired up the pump and sender (color coded) and the gauge reads empty, but i filled the tank...no clue whats up but i would hate to have to drop the tank again....was gonna try soldering the wires together....i only twisted and used heat tube.

 

for help, im going to see if i can solder them without having to drop the tank.

 

re hooked up the t100 outside the tank and it worked great...plugged in the tacoma one and the needle just fell back to empty...ideas?...