Strange goings on with ignition switch?

[BCDC]

Hello everyone, I'm hoping the collective intelligence of the forum can help me with a mystery occurrence that happened a couple of days ago. I arrived home form an outing in the old Benz, then after a little while I decided to move the car outside to the "cleaning area" for a wash but it wouldn't start! The symptoms were, the starter stayed on with no firing of the engine. I moved the gear selector to drive and it stopped turning over, whew! I tried again, same thing. Then I left it overnight wondering if I need to replace the switch mechanism. The next day went out and disconnected the battery lead and tested the barrel with the key to see if the spring back from start position was working okay and it was. After a few tests even removing the key each time I reconnected the battery and the old girl started perfectly. I stopped and started the engine a few times and it performed perfectly. It seems it has fixed it's self. I don't really like this situation, so does anyone know of what could be going on. My car is a reasonably low milage example from 1978 so I would have though the key tumbler and switch would be ok but how could the symptoms change so much overnight? Any advise welcome. Thanks.

BCDC       

[Nabstud]

Have you lubed it up with graphite or similar? Maybe it's just getting a bit sticky

[BCDC]

Yes, I first blew it out with compressed air and little grey gunk came out, then lubed the key with graphite but the key and barrel part seem to be working fine and the spring back is strong, so I'm at a bit of a loss to what happened only that once. Im wondering if there may be bad connections in the actual switch assembly behind the key barrel. I may have to pull the lower knee panel off and investigate further. But if any of the infinitely wise owners of the mighty W116 have any clues I will be very glad to hear from you.

BCDC

[Pete49]

Ihada similar problem with my 450SEL. It turned out the back of the switch (the electrical part) was loose. I removed the unit and re-crimped it and all is well. Remember its and old car and parts can loosen.
Pete

[BCDC]

Thanks, I will do just that.