M38 primer pump

radtech · Post by **radtech** » Tue Sep 05, 2017 6:46 pm

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.

Post by **Ryan_Miller** » Wed Sep 06, 2017 7:24 am

Sounds good!

Thanks for posting the tip, I am certain it will help others working on the primer pumps.

Post by **wesk** » Wed Sep 06, 2017 8:14 am

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.

4x4M38 · Post by **4x4M38** » Wed Sep 06, 2017 12:42 pm

That's what I did.

Then still had to disassemble, soak and clean.

Post by **wesk** » Wed Sep 06, 2017 6:35 pm

You guys must be buying your primers from the wrong guy!!

radtech · Post by **radtech** » Thu Sep 07, 2017 8:18 am

The steel ball pressed into the brass fitting over years can bond together.

4x4M38 · Post by **4x4M38** » Thu Sep 07, 2017 2:02 pm

Either cosmolene or fifty year old gasoline!

radtech · Post by **radtech** » Thu Sep 07, 2017 2:48 pm

There is no gasoline in NOS pumps right out of the original package.They didn't put cosmolene inside the pump.

4x4M38 · Post by **4x4M38** » Thu Sep 07, 2017 4:36 pm

Any idea what's sticking the balls if it's not some sort of lube/storage
fluid?

radtech · Post by **radtech** » Thu Sep 07, 2017 5:02 pm

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.

4x4M38 · Post by **4x4M38** » Thu Sep 07, 2017 5:29 pm

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.

RonD2 · Post by **RonD2** » Thu Sep 07, 2017 9:50 pm

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.

radtech · Post by **radtech** » Fri Sep 08, 2017 6:36 am

New made leather for the pumps is available on ebay and they work great.

4x4M38 · Post by **4x4M38** » Fri Sep 08, 2017 7:13 am

Thanks to you!

radtech · Post by **radtech** » Sat Sep 09, 2017 8:11 pm

New leather will not help if either of the 2 ball checks are stuck to the brass.