That car has a voltage supply relay that powers-up the fuel computer, we replace them all of the time on the 1996-99 diesels.
MB part number 210-540-03-72, list is $105.

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MERCEDES Benz Master Guild Technician (6 TIMES)
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44 years foreign automotive repair
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190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
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