I had mentioned that I thought that it was wilton who had become knowledgable about the Zeniths. I was incorrect, it was wjbell.
Search for all wjbell's posts and read them. I believe you will find them to be extremely helpful in getting your 250 running like it should, which is pretty darn good.
'84 Euro 240D, 516K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in