oil squirters for 964
 

I am looking for info on oil squirters on 964 case. I couldn't figure out how that the little springs inside the squirter that have the ability to hold pressure up to 3 Bar before it opens to cool pistons. Maybe there are heavier spring below in the tube? Could it means the squirters start to flow at .3 Bar instead of 3 Bar?

Blow some compressed air through the squirters and see what pressure they operate at.