timing issue, help! !

My 90 b2200 doesn't run very well. When the number one cyl is at tdc the Mark on the pulley is at about 14 btc. It should be art tdc, but when I do that the piston is moving down. Help me please.

Is your key thing (can't remember the name) on your crank gone? I have heard of some people having this issue. Does the truck run? Or are you doing a rebuild?

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