Question about gun regulator

Asking for a friend

I'm having a hard time getting the right pressure for my paint gun. Here's my setup (in order)

-Small-ish compressor (but with proper piston pump and ~7CFM@90PSI output)
-Some regulator
-water/oil separator after the regulator
-quick connect
-20' 3/8" hose
-quick connect
-gun's regulator
-gun (Devilbiss GTI Millenium)

I have this kit : link

Here's what's puzzling me :

The gun manual is telling me I should use around ~20PSI. No I cannot, for the life of me, get it to run on the "green" zone on the regulator.

The gun's regulator seems to indicate the line pressure?! If I crank up the compressor's regulator to 100PSI, I see 100PSI. If I tune it down, to, lets say, 35PSI, then It seems it doesn't react fast enough and I don't get enough CFM. When I pull the trigger, the pressure, as expected, dips down but it's at 10-12 PSI.. aka, not enough

My understanding of what I should do :
1-Use the maximum pressure I can up to the gun's regulator
2-Use the gun regulator to set it to the recommended pressure

Problem is trying to do #2... the adjustment knob clearly works but I can't see which value I'm setting it at.

Anything I'm missing?

I'm thinking that perhaps something is interfering with the flow (water & oil separator? quick connect).... but the gauge on that gun's regulator is weird.

Regulator

Depends on the regulator but always read gun pressure while the trigger is pulled to the first stage. Also, is it actually a regulator or is it a flow restrictor? A regulator should read output pressure.
I recommend the RTI 1/4" mini regulator. HF disposable water/oil filters seem to work pretty good. Full pressure to the end of the hose. Separator then regulator then gun.
Mine is a DeVilbiss FLG. I run it at 22 psi.

Ok - yeah, looks like it's a flow issue. I'll switch my on-compressor regulator and also switch to high flow quick connect...

Open up the tank regulator to full pressure.

Set your gun regulator to the desired setting.

Without paint in the gun, pull the trigger on the gun.

Adjust the gun regulator so the gun sees the desired pressure with the trigger pulled. Forget what the setting on the regulator is, just set it so the gauge at the gun shows the desired pressure when the trigger is pulled.

You want the regulator to be set while you are pulling the trigger on the gun. It will indicate the same pressure as the tank. But when you pull the trigger, It should drop to 20-30 psi (whatever your manual specifies).

I think that's what you are asking. There are great videos on YouTube on how to set up a paint gun.

Thanks guys - looks like my issue is lack of flow to the gun. I can't get it higher than 12-13PSI with the trigger pulled.

Just ordered high-flow quick connect and a new regulator.

Regulator

Does sound like a flow problem but try it right at the compressor just for grins.
I use 50' 3/8 hose and HF quick connects. Full 120 lbs to the end of the hose.
My RTI regulators show the output pressure when triggered then revert to a few pounds higher. Nice thing is they never drift. Even sitting on the shelf for a month they deliver the same pressure they were set before. Sounds like a commercial. Sorry.

wirejock said:

Does sound like a flow problem but try it right at the compressor just for grins.

Click to expand...

Just did a couple of tests...

Looks like a compound problem. The regulator is the biggest culprit. 2nd is my water & air separator... then the quick connects (which seems only to add a bit of flow restriction)

Thanks!

Depending on the spring size in the regulator, you may have a regulator that is not sized correctly. They will usually say on the data plate what pressure range and flow they are good . Some general purpose regulations are only good adjustable from say 40 to 100 psi.

Many of those gun mounted "regulators" are not really regulators at all, many of them are just flow restrictors.

So I changed the filter, the regulator and the quickconnect to high-flow.

Everything working great now :

https://youtu.be/rg7YWTw6SrU

The quick connects made a HUGE difference

--> https://i.imgur.com/8qV3qnQ.jpg