If you think you have everything calibrated correctly, just increase the infill perimeter overlap by .05 at a time until you get it to stick.
Otherwise, observe the following:
I'm assuming you have the diameter and firmware extruder steps/mm set correctly.
To adjust SF:
To do it right, make/download a 1" cube.
Print said cube with line infill at an infill ratio of 1. The width over thickness should be 1.3-1.5 for the infill and perimeter. 1.3 spans gaps better, 1.5 makes stronger/faster parts.
Start printing cubes. You can stop the print after about the 5th layer to see what the inside looks like.
Increase the flow rate setting until the infill lines are meeting nearly perfectly. you don't want to mush them all together, nor have big gaps. Once the inside looks perfect, then increase the perimeter overlap by .05 until it sticks if it doesn't already.