It isn't your problem, set your pots at 350 (once you figure it out you can play with it). Set your block at 160. once everything is at the proper temps load just a little bit of plastic in the injector and rotate the block up and set the injector in it for 2-3 min. then squirt a little of that plastic in the hole in the block. set the injector back in it and you should see some plastic squeeze out, rotate and slowly load the injector. this should get you a full load, if it doesnt right away try it 2-3 times.
If you still have issues then try replacing the cupped o-rings on the pistons of the injector. there are 4 total and they wont be the cheapest things either.
this should solve the problem you have. It takes a little bit to learn this thing but it is the cats meow when you do, I use mine daily.