I have a powercat airbrush and the gun has been taken apart

most common problem is paint, it is too thick, second problem is your feedline/needle block.

before you put your airbrush apart - remove paint from container, wash well with appropriate solvent, put some of this solvent to the container and try spraying, if no solvent comes out - adjust needle stopper, this is dual action! have needle adjustment! as you did not give the model and manufacturer, this can be only and only general advice!

if still nothing comes out - prepare butcher paper, disconnect airline from the airbrush, disassemble the gun putting the parts on the paper in order in which you disassemble it. wipe off the needle with soft cloth, use drop of solvent if needed. clean body and container assembly and check for liquid flow from container to the nozzle, it should be steady drop, if there is no flow, then use special brush and if you do not have one, soft copper wire of smaller diameter than the passage to clean mechanically the passage. check again for liquid flow. re-assemble the gun, use bit of vaseline or paraffin to grease the needle and moving parts before re-assembly.

use solvent first to check liquid flow. adjust needle, pattern and size of the max flow. remove solvent, put paint into the container and use normally.

in 0.2 nozzle, paint should be of virtually water density... if this is opaque paint - need to be strained as any impurities and bigger chunks will clog the outflow...

hope this advice will help you with your problem - and i do earn some points from you...

wat kind of paint do ypu use?

Solution too thick?low air pressure?

Airbrushes are hand-held and used instead of a brush for detailed work. Spray guns can be either automated or hand-held and have interchangeable heads to allow for different spray patterns.

An airbrush is a small, air-operated tool that sprays various media including ink and dye. Spray guns were developed from the airbrush and are still considered a type of airbrush.

Check this website out, has diagram and description of how it works.
http://www.sidviciousart.com/how-to-airbrush-intro.htm

Hope it helps

It sounds like you have a dirty tip. It doesn't take much to stop the flow to the tip. You need to take the tip completely apart to give it a proper cleaning. Just soaking it won't do.
Hope this helps but if not let me know and I'll try and trouble shoot further.

Make sure the needle is pushed completely up against the tip. You will possibly have to take the back handle off to adjust it. (I am not familiar with this paint gun specifically). Make sure you do not force the needle into the tip, gentley push it until it stops.
I hope this helps.

It is clogged and needs to be disassembled and cleaned with MEK. methyl ethel ketone 

Anest-Iwata brand spray equipment has the most versatile line of airbrushes on the market. Im sure you will find one to meet your needs. well worth the money, it's all I spray

http://www.airbrush-iwata.com/

http://www.tcpglobal.com/airbrushdepot/iwata.aspx

check it out!!