Don't know about the 86s, my 1990 R129 had a similiar thing.

Passenger side, rear wheel ish. Per my mechanic there are 2 fuel pumps and a collection of valves back there. Some type of special, MB specific washers caused the leak. They were cheap, although difficult to get. He was reasonable, couldn't get them so took it all apart and cleaned it, and reassembled / tightened. Seemed OK.
Later that day while he was finishing other things, it started leaking again, and he was able to get the parts the next day, a couple of bucks for the washers, an hour I paid for, and another hour to do it a second time.

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KLK, MCSE

1990 500SL

I was always taught to respect my elders.
I don't have to respect too many people anymore.