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M38 primer pump
Posted: Tue Sep 05, 2017 6:46 pm
by radtech
I have come across several NOS primer pumps and they all had stuck discharge ball checks.The solution is to make a pin punch from a coat hanger,remove the piston then the discharge check plug and push the ball and spring out from the piston cylinder end.Then spray some carburetor cleaner into the discharge port and use a Q tip to swab it out.Reassemble it and it will work fine.
Posted: Wed Sep 06, 2017 7:24 am
by Ryan_Miller
Sounds good!
Thanks for posting the tip, I am certain it will help others working on the primer pumps.
Posted: Wed Sep 06, 2017 8:14 am
by wesk
A quick preparatory step would be to soak the primer overnight or 2 in clean mineral spirits. Then try using the primer to suck in and discharge the mineral spirits. repeat this a few days before attempting the method above.
Posted: Wed Sep 06, 2017 12:42 pm
by 4x4M38
That's what I did.
Then still had to disassemble, soak and clean.
Posted: Wed Sep 06, 2017 6:35 pm
by wesk
You guys must be buying your primers from the wrong guy!!
Posted: Thu Sep 07, 2017 8:18 am
by radtech
The steel ball pressed into the brass fitting over years can bond together.
Posted: Thu Sep 07, 2017 2:02 pm
by 4x4M38
Either cosmolene or fifty year old gasoline!
Posted: Thu Sep 07, 2017 2:48 pm
by radtech
There is no gasoline in NOS pumps right out of the original package.They didn't put cosmolene inside the pump.
Posted: Thu Sep 07, 2017 4:36 pm
by 4x4M38
Any idea what's sticking the balls if it's not some sort of lube/storage
fluid?
Posted: Thu Sep 07, 2017 5:02 pm
by radtech
Steel pressed to brass for years.I just put a NOS suction check valve on a pump I rebuilt with new leather it was packaged in 1952 and the steel ball was stuck to the brass in it as well.I had to use a paper clip to get it loose.
Posted: Thu Sep 07, 2017 5:29 pm
by 4x4M38
Does the new cup and packing kit fix the no flow?
I cleaned my pump completely but old leather packing and cups
I think prevented it from pumping.
I got suction with my finger over the right opening.
Posted: Thu Sep 07, 2017 9:50 pm
by RonD2
4x4M38 wrote:Any idea what's sticking the balls if it's not some sort of lube/storage
fluid?
Could it be dissimilar metal (a.k.a galvanic) corrosion?
http://engineersedge.com/galvanic_capatability.htm
Just my rookie 2 cents.........
.....and from seeing the weird things that happen very quickly to all kinds of metal in a sea-salt environment, courtesy of Uncle Sam! Call me Jar-Head.
Posted: Fri Sep 08, 2017 6:36 am
by radtech
New made leather for the pumps is available on ebay and they work great.
Posted: Fri Sep 08, 2017 7:13 am
by 4x4M38
Thanks to you!
Posted: Sat Sep 09, 2017 8:11 pm
by radtech
New leather will not help if either of the 2 ball checks are stuck to the brass.