I replaced my idler pulley with an ACDelco pulley and the belt isn't sitting right on it. Basically there is a tiny ridge on the inside (closest to the block) part of the pulley that the belt is just barely sitting on. It looks like the pulley is too far out by about 1mm and that causes the belt to sit too far inside the pulley. I've redone it a few times but with no luck. There is a washer (or as some call it a dust guard?) that threads onto the bolt that goes between the bearing and the block and I have heard that these are not needed on pulleys that are not Motorcraft brand and that I should take it off for the pulley to sit flush. Has anyone heard of this?

2000 Ranger, 3.0 Flex.

 

im dealing with the EXACT same issue. and have yet to find a solution