i have a b18a1 and i went through and followed the steps in a manual on how to tighten the belt but it didn't tighen it is still loose
id it the spring on the tensioner that s bad if it isn't tightening ir is there a specail technique to tighten it

 

Set everything to TDC(crank pulley and cam gear marks), make sure tensioner is loose. Install timing belt, here is the tricky part, to tighten the belt rotate the crank clockwise 3 tooth until u feel the belt tight, then tighten the tensioner. spin it clockwise twice and double check your marks. hope that helps.