I like the old style pump because using it, it possible to tell whether the primary filter (in line) is plugged or the secondary (spin on) filter is plugged.

This is determined by the feel of the pump handle while pumping. If the primer handle pulls up hard, the primary filter is plugged. But if the handle pulls up easily and pushes down hard, the secondary filter is plugged.

It ia a rare occasion that both filters need to be replaced at the same time.

I miss the primer pump on my 300SDL.

P E H