alright. im having an issue with the timing belt. i cannot for the life of me get it on the engine right. i've done more then enough of these, but this one just doesnt want to stay correct.

these are where the two marks are:


when i set them the right way, the belt fits real loose on top. then when i turn it to tension it, everything is good, then when i test it and turn the crank 360 degrees counter clockwise it comes up looking like that above. can someone help?