This will not help any. Just a comment. Canvassing the yards for parts,
I see the pump you origonally had in 83 to 84 model S class. The one you got from Ebay I see in 1985 and later models. They also are in the W201 chassis as well.
Haven't taken the time to trace the additional electrical connections on the newer style pump. I got a couple, but have not learned how to test yet.

For now I focus on the earlier model. I do know on the older model, a pressure valve shuts the pump down when it's pressure limit is reached.

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Selling used Mercedes parts on Ebay...always changing...
cdplayer51 take a look!
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