Airbrush problems



Hi please can anyone help. I'm new to airbrushing. I can do a full respray but new to this airbrushing. I have my airbrush all set up and when the trigger is pulled i get a constant air flow. I tested my gun with water but instead of getting a constant flow I got short sharp spurts does anyone know why this is
Many thanks
If you give a little more info, we could help a
What type, air hook-up, etc...
An airbrush will give constant air when you push down and paint when you pull back (while pushing down)...assuming it is a double action brush
Thank you to everyone who has took the time out to read and respond to my thread. I apologise it's a little short and not a lot of info. I'm new to all this and don't know all the lingo yet lol

I have a
Clarke boxer 150ltr tank 3hp motor
In line filter and auto drain
10m 8mm diameter air line

Airbrush clarke cab3-p (model)
My compressor is 14cfm and it's got a maximum working pressure with 10 bar 145psi
I just did a little google on that airbrush and judging by the looks and price tag it is a knock off airbrush and as with all knock off's it is hit or miss with those cheap airbrushes
You'll only need 30psi or less if your doing hard surfaces, fabric tends to be a bit higher but won't be over 100psi
The working pressure on the brush is 50psi

Possible dirty nozzle causing pulsing
Nice one people for your comments/advice I really appreciate it. I've cleaned my airbrush and it's working wonders now Thank you