I've put in a new hand primer pump in 2 other 240D's I've had- I just unscrewed the old one and screwed in the new one... I thought that was all there was to it...
but
I've recently acquired another 1977 240D and have been fixing up small bits and whatnot- I went to swap the leaking old style hand primer pump with a new bosch and when I unscrewed / removed the old one there was a little plunger & spring still sitting in the exposed hole.. ??!! What are these parts? are they supposed to be in there? the other 2 cars I've done this to never had anything sitting in there, just an open fuel line that I screwed the new primer pump to.

I haven't seen any other posts/ tutorials mention anything like this so I'm confused..

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1981 240D ... 265k
1977 240D ... 265k
1977 240D ... 250k

I think those are the guts of the old pump. Remove and replace with the new pump and you should be all set.

X2. I think this old pump can apart before you got to it.

Dan

It would make sense the mushroom ones had a spring or something because you need to pull it out (untighten) and then start pushing. The new ones you just start pushing so they probably won't have that spring.

Dkr.

If the lift pump is the original, older version with fuel inlet on the end, then those aren't the guts of the primer, they're the guts of the lift pump. If they aren't re-used or replaced, then the lift pump will be missing its vacuum check and it will not work.

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'79 240D

Here is the lift pump, I think it is the older style... so seems these parts are necessary..! does the valve and spring really go under the hand primer pump? if so, i better put it back there! I am having a hard time finding a clear diagram or DIY on this style pump and it's rebuild. if this part is supposed to be inside somewhere, not just sitting in the inlet, then I better do a rebuild.
anyone have a link saved to a rebuild of this style?
I found threads talking about it being done, but no DIY or pics (for slower folks like me) seems there is another valve and spring somewhere in the mix too.. I bought this car from a shop that works on w123s so I don't think they would have just put it together wrong, but maybe..

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1981 240D ... 265k
1977 240D ... 265k
1977 240D ... 250k

Thanks Left Coast for the heads up, I never knew about there being an older style pump. upon searching I just found this post with a diagram of this style pump showing the placement spring /plunger underneath the primer pump.

1978 240D lift pump valves

Heading outside now to put these parts back in there!

Then, gonna find the proper rebuilt kit and maybe pull it off and clean it up completely.

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1981 240D ... 265k
1977 240D ... 265k
1977 240D ... 250k

If you are going to rebuild the lift pump, you may as well get one from a later 240D or 300D, and rebuild it instead. The earlier version that you have has a much less robust main spring, and at 36 or 37 years old, it is likely to fail much sooner than the heavier spring on the later pump. It's also the one part that is not easy to obtain. The Bosch version costs a little more than the MB kit, but it has all of the parts, whereas the MB kit is not really a complete rebuild kit.

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'79 240D