What is this little valve and spring from the old primer pump. I recently replaced My primer pump with a new style one that does not unscrew before pumping. Before I did this I tried a used one from the boneyard.Of course it was bad, But it had this little valve. I took the primer off of my car and the spring and plastic valve were not present. Do I need this valve and spring inside my new primer pump? My car is a 83 240d Euro. the donor for the primer pump was a 77 240d. thanks