Did you replace the return hoses? When you did, did you happen to cut one of the barbed ends leaving a tiny grove that sprays fuel out? (Ask me how I know this is possible).

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Charles
1983 300D, bought new, 215k+ miles, donated to Purple Hearts veterans charity but I have parts for sale: http://www.peachparts.com/shopforum/mercedes-benz-cars-sale/296386-fs-1-owner-83-mb-300d-turbo-rebuild-parts.html