I LOVE my autosiphon but not at first. I found that I too had lots of air and it didn't maintain the suction. What I found with mine was that the connection of the transfer tube to the racking cane wasn't tight enough, thereby letting in enough air to disrupt the process. I placed a clamp on the connection point of the tubing and racking can and voila....no air. As far as starting the siphon, two pumps get it going to a trickle and then I squeeze the tube just below that clamping point. This forces that suction to push all remaining air out and I maintain a full suction all the way to the trub.
The clamp is a small one used for keeping computer cords tidy.
Hope this helps you as much as it did me.