Help with airbrush not spraying

[john]

I sold an Ammo Airviper airbrush and the customer said it didn’t work, so I got it back off him and tried it myself, it’s not working right, I’ve given it a full clean in the sonic cleaner and when I press the trigger air comes out but no liquid (water for testing) the only way I can get it to spray right is put my thumb over the cup, so it must be something to do with the air not getting to the right place, has anyone else ever had a similar issue?

 

[stillp]

That's really strange - I'd have thought that putting your thumb over the cap would be more likely to stop the flow of paint.
Pete

 

[Mark1]

Never had a problem a clean didn't solve other than that i agree with what pete said.

 

[Jim R]

Sounds like a seal either missing or not seated correctly.

 

[JR]

No John.
Looks a decent ab from looking at a review on Y tube. Only a .2 needle

 

[john]

Looks a decent ab

They are made by Badger for them.

 

[stillp]

Does the liquid in the cup bubble John?
Pete

 

[Andy T]

Does the liquid in the cup bubble John?
Pete

Ha, I was just typing that

 

[john]

Does the liquid in the cup bubble

No, the water doesn’t move at all

 

[stillp]

If the water doesn't move then the air isn't building pressure in the cup when you cover it with your thumb, so the only thing I can this is that when you cover the cup you're pressing down on it which somehow makes the air go where it should. Is there a hairline crack in the body of the a/b perhaps?
Pete

 

[stillp]

Ha, I was just typing that

Fools seldom differ Great minds think alike.
Pete

 

[john]

d. Is there a hairline crack in the body of the a/b perhaps?

I blocked the nozzle and put my finger on the cup and couldn’t see any water escaping from cracks, couldn’t see anything under a magnifying glass.
If I block the nozzle the water bubbles in the cup, I’m wondering if it’s been fitted with the wrong size needle for the nozzle or vice versa, I will get a new set tomorrow see if that fixes it

 

[stillp]

HAve you tried pressing down on the cup without sealing it off with your thumb? Is there a seal at the bottom of the cup where it goes into the airbrush?
Pete

 

[Tim Marlow]

Pete’s ideas are good ones.
There is possibly an air leak between the cup and the AB body, or between the nozzle and the body. When the brush is activated the water isn’t pulled through, just the air at the leak….pressing down or covering the cup is somehow sealing the leak…..

Water has quite a high viscosity so air is potentially being preferentially pulled in to the leak as air is easier to suck through than water. The airbrush therefore won’t spray.
Another effective idea is to leak test the body and cup under pressure. If you make up some dilute washing up liquid solution you can use a paintbrush dipped in the solution to look for leaks. Block off the nozzle and the cup, activate the air, and paint the body with the soap solution. Any air leaks will show up as bubbles. Its how we used to look for leaks on fermenters and is effective down to really small faults.

 

[john]

I’ve changed the needle, nozzle and nozzle cap and it’s still not working, I’ve asked them to send me a replacement body, it can’t be anything else.