Door Locked from outside but not inside?

[rs.autoart]

I just bought my first pair of project cars, (two '76 280Zs and I am PSYCHED about them!! ) and both doors on both cars are locked from the outside, but not the inside. I can climb through the hatch and open the doors fine from the inside, and the lock isn't down inside, but once I exit the car and close the door, it is locked! is this some kind of safety feature? is there a way to undo it? or is something broken/stuck? i haven't tried using the key to unlock it (just thought of that, whoops); would that help? (maybe i should have tried that xD). any help would be appreciated, thanks!!

[Reverend]

So the knob aint down but the door is locked? And you can lock it outside but not unlock? The door locking mechanism is busted somehow, download Factory Service Manual, remove the door panel and tell us what you see. I had to fight with my doors too.

[SteveJ]

If the door locks automatically when the door closes, the problem is likely that the door mechanism has lost a tension spring. I had a similar problem with my 260Z. I purchased a used door mechanism from Zbarn and noticed the spring that was missing from mine. I was able to fabricate a replacement spring easily.

While you have your door apart to remove the mechanism, it's a great opportunity to replace things like the window channel insulation.