I've never used my primer pump but after a lot of reading decided if I ever did need to use it, it would likely fail. I ordered a replacement - new style with the black top.

On the old pump, it is marked with a direction to turn before pumping, right? After pumping you seal it back down in the opposite direction, right? BTW - mine seems to be frozen shut after 25 years.

The new style has no markings and as received turns freely in either direction. Does it not screw down to seal after pumping? If so, which direction?

I've not installed it and looking at it here in my hand, I can see the pump design but not a sealing method. Am I missing something?

It will remain on the shelf till I know more.

Yes, it's for the 1983 listed below. Original pump has never been needed as I have never run out of fuel or failed to fill the filter when replacing.

__________________
Charles
1983 300D, bought new, 215k+ miles, donated to Purple Hearts veterans charity but I have parts for sale: http://www.peachparts.com/shopforum/mercedes-benz-cars-sale/296386-fs-1-owner-83-mb-300d-turbo-rebuild-parts.html

The Bosch pump does not "lock down." Install it and be happy.

That's what I was expecting - thanks for the confirmation.
So, if I need it in the next 25 years, I just start pumping. Right?

I suspect the fact that mine is frozen is the only reason it isn't leaking based on what I've read.

__________________
Charles
1983 300D, bought new, 215k+ miles, donated to Purple Hearts veterans charity but I have parts for sale: http://www.peachparts.com/shopforum/showthread.php?t=296386

Right. Let's just hope that we have something to pump 25 years from now!!!