Touch-up gun pulsating

BBPanel

BBPanel

Promoted Users
I have an old (~50 yrs) touch-up gun I use for very small volume primer shooting. It pulses paint, i.e., it will shoot and then stop then start, etc. It just started after so many yrs of working just fine. I've cleaned it multiple times, tried varying pressures, etc. The air flow is consistent but the paint discharge is not. Anyone have an idea why its doing this?
 
BBPanel said:
I have an old (~50 yrs) touch-up gun I use for very small volume primer shooting. It pulses paint, i.e., it will shoot and then stop then start, etc. It just started after so many yrs of working just fine. I've cleaned it multiple times, tried varying pressures, etc. The air flow is consistent but the paint discharge is not. Anyone have an idea why its doing this?
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Since it's old and doesn't get used much, the seals may just be dried up, some of the early guns used leather needle seals which needed to be moistened from use or they would loose there sealing ability. They could be taken out of the gun and soaked in thinner to re-soften them or replaced. tightening the nut at the needle seal aera may be all it needs, but too tight and you cause other problems. Replacement seals are available for most older guns still.
 
This is not my gun but its very similar. I've checked all the passages, vent, etc. I've put my finger over the vent and shaken the cup - no leaks. Seals looked ok but I can check them again. I have tried tightening the needle seal nut.
touchup.jpg
 
BBPanel said:
This is not my gun but its very similar. I've checked all the passages, vent, etc. I've put my finger over the vent and shaken the cup - no leaks. Seals looked ok but I can check them again. I have tried tightening the needle seal nut.
View attachment 24089
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Do any of your adjustments change anything? better or worse, I don't know if your gun has a nozzle seal, but those can get cracks also and replacement is the only option there.
 
Nope, nothing changes anything. Viscosity also doesn't make a diff - laquer thinner or epoxy does the same thing.
 
Most likely the nozzle seat. A beveled mechanical 'seal'. Wore out... apply some anti seize compound on it as a test.
It's loosing suction on the cup tube,allowing air to break the vacuum,if it's not leaking product around the needle packing nut and the vent is clear.
Far outside chance is the cup nut connector which is a bevel seal as well.
 
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I had a similar problem with mine ( it was the Binks 15 touch-up gun) after I cleaned it and got it all ready to loan it to a friend to use. It "spit" and pulsated over just about every pressure range he tried with a paint running about 21 seconds in a Ford 4 cup.

I didn't want everything so tight he could not take it apart to clean it. At 85 years old at the time, he would have taken everything apart whether it needed it or not to clean. I had my fluid nozzle threaded into the gun snug but not so tight that my friend could not loosen it with the wrench that came with it and hold the gun in his hand while doing it. I took it back to the jobber I bought it from and he put it in a machinist's vise with soft wood blocks to protect it and gave it a real good tightening and my friend was back to painting in about an hour. It was much tighter than what I was able to do by holding it with my left hand and arm and tighten myself without the aid of the vise. It has worked like a charm for me making sure it is damn tight now before I use it. Mine needed to be a lot tighter than I thought is should be
 
Well, I've tried/looked into all suggestions mentioned here and no luck. I've purchased an inexpensive replacement just for shooting primer - need something to keep things going. Should I discover the "cure" in the future I'll report back. Thanks.
 
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