Petromax 828 pump sometimes overshoots while pumping

Hello, happy with my new, but very old, Petromax 828 350 CP. Only one small problem... Sometimes the pump overshoots while pumping. Most of the times it works fine, but sometimes the pump goes in very fast without resistance. The pump leather seems ok, it's soft and supple. Any ideas?

 

It will be the pump leather, or a too loose connection of the pump cup fitting, that causes that problem.

Rough up the outer surface of the pump cup, re-oil it, and splay the end somewhat before re-filling into the pump tube.

Cheers

Tony

 

Thanks, will try to fix or find a new one!

 

If the pump cup is not split or cracked, you probably don’t need a new one.

Tony

 

Ok, how do you rough up the pump cup?

 

I use my thumb nail.

Tony

 

Thanks, it worked out!

 

Haha, you're Under My Thumb! #rollingstones

 

I normally get the plunger out, hawk tuah spit on the leather (with some sewing machine oil) and bend the cup slightly outwards.