I say replace the hose with the correct one.

By the looks of it your engine isnt a cali engine so you would need this hose for the wastegate.

http://catalog.worldpac.com/mercedesshop/sophio/quote.jsp?clientid=catalog.mercedesshop&cookieid=25H0WHBKK25H0WHKL7&baseurl=http://catalog.peachparts.com/&partner=mercedesshop&year=1983&product=B4034-11582&application=000005727


The updated primer pump is this one.
http://catalog.worldpac.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=25H0WHBKK25H0WHKL7&year=1983&make=MB&model=300-SD-002&category=All&part=Primer+Pump

Id also recommend replacing the old fuel lines that could also leak due to age.

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