I think it's suppose to be 400 PSI. I believe 250 PSI is about the lowest you can expect it to run. I'm not sure these are the specs, but I have read these numbers on this forum. Do a search and you will probably be able to find more.....

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1976 240D
1987 560SL
2007 E320 Bluetec
1998 C280 (now son’s car)
1982 240D Manual - Sold