First: be sure that you are using genuine Kanger heads as the knockoffs have many issues.
Second: if you are using a 50/50 blend of e-liquid or a higher VG juice, your may need to remove one or both of the flavor wicks that rest on top of the coiled wick. Take those short, strong, unpowered primmer puffs. If you see the bubbles rise in your tank, you know it's wicking properly.
Third: Take out your atomizer head, pull off the top "chimney" of your atomizer and check your coil. Does it look deep brown? Does the coil looked gunked up? If so, soak your head in vodka or HOT water for a few hours, then give it a dry burn, blow off any gunk, and reassemble. Be sure that your wick is white before putting it all back together.
Fourth: there is a small chance that your coil has shorted out, or you have burned through the insulator on your atomizer head. Take everything a part, examine your coil and be sure that no part of the coil is touching the metal cup that it rests in. If you can, examine the "cream" colored insulator from the top and bottom and be sure that you haven't burned though it. This will be hard to see, I recommend using a flashlight. If the insulator is toast, chuck it all out. Sometimes, the factory heads aren't quite right and will burn the insulator, resulting in a burnt rubber taste.
Hopefully one of these things will help you! Vape on!