On Mon, 07 Jun 2010 20:47:51 -0500, Steve Turner
wrote the following:

On 6/7/2010 7:47 AM, Larry Jaques wrote:
On Sun, 06 Jun 2010 21:38:47 -0500, Steve Turner
wrote the following:

On 6/6/2010 7:16 PM, Larry Jaques wrote:
2 possibles:

1) Verify that the rear needle o-ring (#16) is in there.

That o-ring is there; I know because I removed the needle several times and I
could feel it providing that nice snug resistance. I could also see it sitting
in there when I removed the #17 nut.

2) Verify that the o-ring, (#9) and packing (#10)on the volume nozzle
are in there. It can't suck fluid up the siphon tube if it can't pull
a vacuum with the venturi action.

Thanks Larry; I will check for those.

You do have a rubber-tipped air blow gun, right? They make cleaning
small orifices much, much easier. Doublecheck your flow from each of
the fluid nozzle orifi (orifizzes? while you're at it.

I learned to triplecheck everything when I was doing tune-ups and
rebuilding carburetors for a living. And to this day, I can still
honestly say "HOLLEY SUUUUUUUUUUUUUUUUUCKS!"

Ok, I just spent the last two hours understanding ever little aspect of this
gun, and all I can conclude is to either: 1) take the damn thing back
(assuming I can find the receipt); or 2) throw the damn thing away. There is
nothing *wrong* with it, it simply won't pull a vacuum.

Referring once again to page 12 of the manual:
http://manuals.harborfreight.com/manuals/0-999/86.pdf

There are only two air paths through this gun, and both exit through the air
cap with no connection whatsoever to the fluid path. The "main" path causes
air to flow out of the two tiny little air holes in the air cap on either side
of (and very close to) the central opening that the fluid passes through; the

That's your 'venturi vacuum principle'.


second path (which can be closed off completely by the "volume adjusting
screw") passes through the larger air holes in the "wings" of the air cap.
Closing off this air path should simply cause a mostly useless, and poorly
atomized round pattern, but it should not affect the gun's ability to draw a
vacuum.

My air cap has a small aperture around the main brass valve (holding
the needle) and several very tiny holes in the air cap. This combo
provides the vacuum-assist for gravity fluid flow behind the needle.


My conclusion is that drawing a vacuum is the job of the first air path;
because there is NO air path into the fluid path, there is no pressure of any
kind "forcing" or "coaxing" the fluid to come out.

It's a very, very subtle pull when working right.


The very strong blast of
focused air coming out of the two tiny nozzles in close proximity to the fluid
opening is what should be drawing the fluid out, and this simply isn't
happening. There are no blockages (or leakages) anywhere; this gun is as clean
as a whistle and I've verified all air paths until I'm blue in the face.

One funny little experiment I ran was to disconnect the fluid cup and all its
fittings from the body of the gun, then I actuated the trigger and checked for
vacuum in the fluid path by putting my *tongue* over the fluid input port, and
I could detect no vacuum whatsoever.

Use a milli-vacuum gauge, Steve. You're -not- pullin' 30 inches o'
Merc on a gun. vbg


Where's nailshooter Robert when you need him? I'm pretty much ready to toss
this gun and get one of the gravity feed models instead...

That's what I did. HF 43430 HVLP gravity fed beastie.

How long have you had this gun? If it's new and you're using HVLP
pressures, maybe turn up the air a whole bunch for proper action.
My tip says "10PSI Max" but I had warmed and thinned the latex paint
and ended up turning the pressure up to about 30 before I got any
flow. Yeah, I know, I needed a 30mm needle kit.

--
Never tell people how to do things. Tell them what
to do and they will surprise you with their ingenuity.
-- George S. Patton