I was able to work on the lock yesterday. It was a relatively easy fix. It would have been real nice to have a new cylinder, but this will do for now.

After I cleaned everything up, I was able to see how everything was supposed to work. I finally figured out that one of the tumblers was broken. When the key was inserted, instead of sliding into the cylinder smoothly, it would slightly cock sideways. This would cause it to bind. Since I did not have another tumbler, I just removed it.

I thought I had everything figured out. I put the handle back in the car. Before I reinstalled the interior panel, I tried the operation. I still could not get it to unlock. I finally noticed a very slight burr on the inside of the door handle. When the bad tumbler would cock to one side and bind, it created the burr over the years. I cleaned that up and everythng is as it should be. I have just a little less lock security now, but not much less.

Thanks for all the comments.
Doug

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1980 Mercedes 300 SD, 215,000miles
2001 F-350 Powerstroke turbodiesel, Crewcab, 4x4, 81,000 miles
1993 Chevy Suburban, 185,000 miles