Grease gun Questions

[Skyco]

I've ended up with several grease guns over the years. I noticed the spring that keeps pressure on the cartridge can vary greatly. I have one old gun that has such a strong spring it is all I can do to pull the plunger out against the spring. That one never quits pumping Other newer Chinese ones have much weaker springs and can be problematic

 

[Slacker]

Put it in the sun for an afternoon, fitting down. That has cured mine a few times.