Not sure if this'd cause your problem, but aren't you always supposed to replace the crush washers as well when doing the delivery valve o-rings? I was searching around for similar info the other day and I think I saw a couple of posts about this, and about problems that could crop up if you didn't do the crush washers as well.

good luck,

dave

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1987 190d turbo, 5-spd conversion -- 146k
1973 280 -- back on the road with a euro m110
1980 300SD -- RIP - Sold for parts (lost battle with rust)