Thanksgiving 1945 Milspec Mystery

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MiguelHerbert
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Joined: Wed Aug 12, 2020 10:39 pm

Thanksgiving 1945 Milspec Mystery

#1

Post by MiguelHerbert »

I am working on a '45 Milspec where--once again--I am perplexed.

I did a thorough cleaning of the fount with citric acid and the BB Dance--with great results. Decided to jump ahead in the project to test for any pressure issues before starting an overall spruce up.

Filled the fount about 1/4 with isopropyl alcohol, and pumped her up--when at about 20 strokes--alcohol came spewing out of the the thumb hole of the pump. I mean, REALLY squirting out. Never had that happen before--fuel actually flying out.

I've gone through the following process: replaced the (seemingly functional) check valve with a (seemingly functional) used one, and nothing changed--still blowing out alcohol. (By "seemingly functional") I mean--after using carb cleaner--the valves both passed the good ole suck-n-blow, plus rattle test.) Also: I had applied some thread sealer to both valves just for yucks.

I then super-cleaned out the fount pump shaft with carb cleaner and thoroughly scoured it clean with a rag. Inspected the tube with a flashlight, and could see no pinholes in the shaft, or degradation of the brass surrounding the check valve.

So, I changed out the leather pump cup while I was at it, and put in a THIRD (used--seemingly functional) check valve, this time with no thread sealant.

The only change is: after about twenty pumps, there is no alcohol shooting out of the thumb hole, only pressurized air that smells of alcohol. The fount will not not hold pressure, even for a short while.

I am thinking there has got to be a signifigant pressure leak in the pump shaft--but can't see a darn thing.

Your take, folks?
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Trout
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Re: Thanksgiving 1945 Milspec Mystery

#2

Post by Trout »

I always check pump tubes like this:
Empty fuel from fount and tighten fuel cap.
Remove pump but leave the pump rod screwed down.
Pour a little DNA, down pump tube.
Warm the fount with your hands or set it in the sun and watch for bubbles in the pump tube.
Mike
If a man made it, a man can fix it - My Father
ICCC 1473

MiguelHerbert
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Posts: 124
Joined: Wed Aug 12, 2020 10:39 pm

Re: Thanksgiving 1945 Milspec Mystery

#3

Post by MiguelHerbert »

is DNA denatured alcohol?
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Trout
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Re: Thanksgiving 1945 Milspec Mystery

#4

Post by Trout »

MiguelHerbert wrote: Thu Nov 25, 2021 8:40 pm is DNA denatured alcohol?
Yes Sir.

You could use what ever you have , isopropyl, carb cleaner or even water. DNA is easier for me since I use it in the founts after cleaning anyway.
Mike
If a man made it, a man can fix it - My Father
ICCC 1473

MiguelHerbert
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Posts: 124
Joined: Wed Aug 12, 2020 10:39 pm

Re: Thanksgiving 1945 Milspec Mystery

#5

Post by MiguelHerbert »

I don't understand--if denatured alcohol bubbles come out of the pump tube, how do you pinpoint where the breach is?
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Trout
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Re: Thanksgiving 1945 Milspec Mystery

#6

Post by Trout »

If you can't see where they emerge from then the pressure is making it too rapid and the bubbles are too big. Release the air pressure and start with only one hand on the fount to keep the pressure low and the bubbles will be smaller and slower.
Or just wait until the pressure diminishes from air escaping the fount.
Mike
If a man made it, a man can fix it - My Father
ICCC 1473

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