I have a 1983 300SD and when i turn the key to the off position it does not shut off. However if I turn the key back and forth i can find a spot where it will kill the engine. I am assuming the it has something to do with the vacuum shut off control or the vacuum lines. I think it could use a new ignition tumbler but I don't think that is what the problem is. I removed the underside of the dash (not sure what you call this but it is carpeted and is part of the venting system) Anyway when I crawl under there and look at the ignition lock housing I can see where the vacuum lines connect. At this connection I can see some sort of black goo. First of all does anyone know what this goo could be and what I should do about it? Secondly, if I need to replace the ignition lock housing do I just need to remove the instrument cluster to get at it? Thanks for the help.