Siphon-feed spray gun won't siphon

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After a fair number of positive reviews in this group I decided to pick up this spray gun a few months ago from Harbor Freight:
http://www.harborfreight.com/air-tools/paint/touch-up-air-spray-gun-86.html
I used it once (probably to spray some clear lacquer; don't remember), cleaned it (I've been using and cleaning out spray guns for over 30 years, so I'm no dummy at this), and put it away. Pulled it back out this morning (that's what she said) and tried to spray some Zinsser white shellac primer, and... nothing. Lots of air flow, but no white fluid is coming out of the nozzle (that's what she sai... er, never mind). Thinking there must be a clog or obstruction somewhere, I started disassembling things and checking for problems, but found nothing. Before I start talking specifics, those who pretend to care about my piddly little problem might want to refer to the parts listing on page 12 of the product manual:
http://manuals.harborfreight.com/manuals/0-999/86.pdf
Ok, so there are no obstructions anywhere: air is flowing from all the ports in both the air cap and fluid nozzle; I've adjusted the fan adjusting screw just far enough out so that the trigger has full travel (but no more) which allows the needle to open according to the trigger pressure, and it retracts to the fully closed position when the trigger is released. The volume adjusting screw (which controls the amount of air flow to the "wings" of the air cap, which in turn controls the amount of "fan-out" to the spray pattern) is working properly, and you can feel the air flow from the air cap change as adjustments are made; I was running it wide open, but its position makes no difference.
No matter how I adjust any of those contraptions, no fluid is being pulled from the cup. And yes, the pressure release air hole in the top of the cup is open, and the shellac is sufficiently thinned for spraying. In fact, the cup can be filled with straight denatured alcohol and it makes no difference; no siphoning action is occurring. I can even remove the cup and stick the siphon tube into a separate container of denatured alcohol, and still nothing. HOWEVER, if I remove the gun from the cup, turn it upside down and fill the siphon tube with fluid, VIOLA - It sprays! If I disconnect the gun from the air supply, fill the siphon tube with thinner (still upside down), and actuate the trigger, a steady stream of thinner runs out the nozzle and is depleted, just as I would expect. EVERYTHING is working as I'd expect, except no siphon action is occurring; I'm befuddled.
Any ideas?
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On Sun, 06 Jun 2010 17:06:45 -0500, Steve Turner

2 possibles:
1) Verify that the rear needle o-ring (#16) is in there.
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.
Broken/missing parts 9, 10, and 16 are the most probable causes, Steve. Never leave 'em in carb cleaner overnight. DAMHIKT
-- It is not the strongest of the species that survives, nor the most intelligent, but the one most responsive to change. -- Charles Darwin
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On 6/6/2010 7:16 PM, Larry Jaques wrote:

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.

Thanks Larry; I will check for those.
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On Sun, 06 Jun 2010 21:38:47 -0500, Steve Turner

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!"
-- Never tell people how to do things. Tell them what to do and they will surprise you with their ingenuity. -- George S. Patton
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On 6/7/2010 7:47 AM, Larry Jaques wrote:

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 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 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. 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.
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...
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On Mon, 07 Jun 2010 20:47:51 -0500, Steve Turner

That's your 'venturi vacuum principle'.

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.

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

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

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
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** 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... **
Where indeed!
More importantly than where, is what has he been doing? Working on some new emergency work contracts. A few really windy storms did a lot of damage here last Friday, and I have a lot of brand new "best" friends that are looking to have their domiciles secured. We have 40% chance of thunderstorms Tuesday, Wednesday, and 30% on Thursday. I almost have more than I can deal with now. I haven't had this volume of calls in a year or more... lots of panic amongst my customers!
"Big Guy... you know what we call "crisis" in sales? (Taps his head knowingly...) OPPORTUNITY!"
Herb Tarlek, Sales Manager WKRP - Cincinnati
****************** There aren't really a lot of places for any of these little guns to go wrong. More importantly, almost all MY personal spray gun problems have come down to 1) improper cleaning 2) reaction of materials in the gun to one another causing almost invisible material clots 3) improper assembly.
It is hard to diagnose without seeing the gun in person. That aside, I am thinking that Mike probably hit this one (although it may seem improbable to you) early on. I'd be the problem is in the siphon assembly. Somewhere.
There have been good posts that address all the likely suspects, but it sounds like you have done a pretty good job on your own.
On the other hand, you may have a bad gun. Doubtful, but possible.
I am sure you are taking the gun apart correctly and putting it back together correctly as well, so I won't bother with that.
I would take the gun apart again. This shouldn't take too long, especially in the light of the fact you can probably do it blindfolded now. Re-clean the inside of the housing chamber where the packing and the retention nut for the packing go between the fluid nozzle ( #4) and the packing and nut ( #16 and #17 ).
Take a BRIGHT flashlight and see if you can peer INTO the housing and carefully inspect the needle packing area as well as well as the area for the volume adjustment. These must be spotless. Everything inside the gun housing must be spotless.
Use a gun brush to clean the inside, the threads. Use a toothpick to clean the threads to see if anything comes off. Since this gun is dead, if you find something you can't get off, try some paint stripper on your brush and brush the inside of the housing out to see if anything comes out. Don't leave it in too long as it will peel off the chrome. Put it in brush it vigorously, then rinse it out.
After yet another full inspection, and making sure you are installing all parts, reassemble. When you assemble, start at the back of the gun and put in the needle assembly, packing, nut, etc. On the needle, put a small amount of petroleum jelly on the length of needle all around it. If the packing is good, it will skim off the jelly it doesn't need and you can clean it off with a towel. This will make your trigger much smoother and easier to shoot, and seal a bit better as well.
Put the trigger on.
Assemble the volume adjustment group. It is tempting to put in the ring/washer, then the packing, then the retention nut, then the screw. Try it this way: install the screw into the retention/receiver nut. You don't have to screw it in all the way. Once you have it seated well, put the packing ring over the end of the needle, then add the washer on top, then install it all into the housing. Before final assembly of this group, put some petroleum jelly ( a bit ) all over the packing ring to make sure the needle isn't sticking to it. It is possible that a deformed packing ring (from assembly or sticking to the screw) has added to your problem, and this could help prevent it.
As a sidebar, take a look at the volume adjustment screw. Some of them are different than others. On some models, the screw is hollow to facilitate material movement. If you have a hollow screw, then make sure both ends are perfectly clean. If it feeds material through the screw, the tiniest piece of debris will foul your gun.
Now you have everything put together except the things in front of the housing. Open the volume screw about half way. Hold the gun securely in one hand, and an rubber tipped air nozzle in the other. Insert the rubber nozzle in the fluid nozzle seating area way to create a bit of a seal. **Gently** open your air and see if any air comes out the bottom of the head. If it doesn't, open the screw all the way and see if you can get any debris to come out. If that doesn't work, close down the needle, the put the air in from the underside of the gun and the flow should come through the hole where the fluid nozzle goes.
If no air comes out, try increasing the air. You have probably found the blockage.
Take a really hard look at the fluid nozzle. Run a toothpick through the nozzle <from the back> until it pokes out of the fluid tube where the needle sits. DO NOT push your toothpick through from the front as you can easily leave debris that will re-clog your nozzle. If you can see unobstructed daylight (again, hit it with the flashlight) then after making sure there is nothing at all in the air ports, attach to the gun.
Finish the assembly of the head.
Last, take a look at your pickup tube. Before installing you should be able to hold it up to the light and see all the way through it, and it should be clean as a whistle. If it is, install it.
Once again, make sure you can see through the vent hole in the cup lid.
Try opening the air all the way (no more than about 20 lbs from the compressor, all the way on the gun), and the fan about half way. Try shooting some water through it.
Honestly, I would be surprised if you didn't cure it with all of that. There just isn't much to go wrong with these guns. I just sounds like a bad seal, bad seal placement, or a small piece of debris got past you when cleaning.
But knowing that the most I have paid for either of the two I have was $10, I wouldn't have my feelings hurt to go buy another or ask for a replacement.
Let us know....
Robert
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My syphon gun puts pressure into the container when i pull the trigger, Its acting like air pressure is bypassing somewhere, ive had it apart too many times, thereis a plunger valve with 3 seals on it, could air be by passing one of the brand new o ring seals ?
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My syphon gun puts pressure into the container when i pull the trigger, Its acting like air pressure is bypassing somewhere, ive had it apart too many times, thereis a plunger valve with 3 seals on it, could air be by passing one of the brand new o ring seals ?
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On Sunday, June 6, 2010 at 5:06:45 PM UTC-5, Steve Turner wrote:

Or it could be something as simple as a blocked vent hole.
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Try again Dr. Deb.
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snipped-for-privacy@slp53.sl.home (Scott Lurndal) wrote in writes:

Gonna guess that in the 6+ years since Steve asked his question he's figured out a solution, so trying again probably isn't necessary.
John
(who wishes Google wouldn't link together totally unrelated ancient threads.)
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That's how threaded Usenet discussions work. For whatever reason Dr Deb decided to reply to the thread originator (Steve Turner) instead of the the thread reviver (basshammer5x4x3x2x).
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On Friday, September 23, 2016 at 9:56:59 AM UTC-5, Spalted Walt wrote:

Well, that's apparently how threaded Usenet works....
I see where Basshamme has continued the thread, today. He/She, apparently , is having the same problem, today, as Steve had long ago. He describes a similar problem and Dr. Deb replied to Basshamme, not to Steve. *********************************************
Re: snipped-for-privacy@gmail.com     
4:05 AM (7 hours ago)
My syphon gun puts pressure into the container when i pull the trigger, Its acting like air pressure is bypassing somewhere, ive had it apart too many times, thereis a plunger valve with 3 seals on it, could air be by passing one of the brand new o ring seals ? ******************************************
Sonny
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Are you a betting man, Sonny? (;
Subject: Re: Siphon-feed spray gun won't siphon Newsgroups: rec.woodworking
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wrote:

No, it's not how Usenet works.
Usenet has a header called "References" which is used to thread discussions. That header exists specifically because you can have multiple threads with the same subject. Unfortunately, the folks at Google are ignorant of that header (or purposefully chose not to use it, which is worse)(*), so they mash together all threads with the same subject line.
In this case Google has joined basshammer's current thread to some ancient thread with the same title, and confused Dr Deb as to which posts are current and which are not.
John
(* I'm convinced Google uses Groups as a dumping ground for folks they don't want to fire, but are too incompetent to work on anything Google's really interested in).
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Yes, actually it does.

Had you bothered to look at the "References" in the header of basshammer's post(s) you'd realize how ignorant/uninformed/wrong the rest of your reply actually is.

The entire thread link is below. Examine it closely, then report back on which posts Google fucked up...
https://groups.google.com/forum /#!topic/rec.woodworking/fdvJX_-wNdo
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Well, all that usenet stuff is irrelevant. Seems, Basshamme is now havin g problems with his siphon gun and the point is to help *Bass.
I suppose he is having a similar issue as Steve had. I would also check t o make sure the siphon tube is connected, tightly/securely (missing o-ring or seal?), at its upper end, inside the cup. If everything (cleaning, eta l) checks out ok, yet still sucking air, only, and not the finish/liquid ma terial, then air may be coming directly from the vent hole to the upper tub e, bypassing the liquid in the cup. Suction may be there, inside the cup, but not through the whole length of the tube.
Sonny
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On 9/23/2016 3:55 PM, Sonny wrote:

+1
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Actually "all that usenet stuff is" very relevant. It is SUPPOSED to help prevent misdirected replys like you just did.

Which is why you should be posting your helpful reply to Basshamme, instead of me. Will he even see it now? Who knows.

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