Had a problem that after a month of storage, car wouldn't start.
Troubleshot problem to no power to fuel pump. disconnected hot wire to pump and hooked up 12 volts, car started and ran fine. After about 12 hours of looking for the fuel pump relay finally found it. Of course it's labeled as the kickdown relay which didn't help finding it. Finally figured out from a set of 500SEL diagrams the fuel pump and kickdown are shared by the same relay. Anyway, tapped on it and the car started. Either stuck inside or a loose connection. It's marked 80 6376 000 but I can't find anything by that number. Anybody have the correct Mercedes part number. This feels like a problem that will come back..

DR

I recently had "high idle hell" with my '86 560SL which had been sitting for a month and a half, as well as an ABS light problem. I removed the OVP relay, reseated it, and the problem hasn't come back in a month. I haven't looked inside of one of these but if it does contain a mechanical relay, theoretically, they can stick over time.

More likely, I think that the relay plug pins and their socket contacts on cars of that era were silver or some precious metal plated. but sockets like these lose their "spring" over time, and it's possible that letting the cars sit might cause a marginal contact to corrode. In my case, not helping is that my new house has a garage facing south and temps in the garage can actually go over the outside temp in the late afternoon (I'm working on this problem).

Moral of the story: don't let the car sit.

__________________
86 560SL
With homebrew first gear start!
85 380SL
Daily Driver Project

http://juliepalooza.8m.com/sl/mercedes.htm

Same problem with my 84 500sl. I pulled the relay and found a broken solder connection and I resoldered it but the problem came back a few months later. The best way to go is replace the relay with a new one because if the problem happens on the road you will then have a real problem