Lube the door end of the U at the rear middle of the door. It has to pivot freely for the spring to allow the door to open. Right pic in this link:
Hiya Brass,
Actually, I'd take it a step futher than Karl suggests. I'd pull the sliding hinge link assembly (the mechanism at the rear of the door which incorporates the "U" link) out of the door and go through it thoroughly. That would be a complete cleaning, replacement of shot parts, and (as Karl does suggest) lubrication. You'll probably need to visit a boneyard if you do wind up needing parts. But this way you'll have a door which works (and will continue to work) as designed.
Mike
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