W123 proper diesel lift pump?

Hi, interesting idea. However, I think you're over-thinking this big time. If you follow the fuel filter change guide and fill up the large spin-on primary filter with some type of fuel before re-installing it you may not even need to prime the car. I know last time that I didn't even bother pumping the hand primer and the car started right up. However, if you do need to prime the system a bit, it'll just take a few quick pumps of the hand primer.

As an aside, your W123 is a later model, so it probably has the black plunger style primer pump. If so, these work very well. If you happen to have the older white plastic screw style primer pump you should consider changing it out for the new style. There is a guide for this on the main W123 page. It's an easy swap, and only costs about $15. Then you'll have a good primer that you can rely on.

Basically, don't stress priming so much. Fill up the filter, pump a few times, and then crank away!