How do keep the belt from popping off?

The Alternator belt in my car keeps popping off... We changed the tension pulley but it still isn't acting right...

My car is a 1993 Pontiac Grand Am SE

4 cyl and its a single... I believe....
How do keep the belt from popping off?
If it's the right belt for your engine and you have a new belt tensioner on it and have the belt routed right there is no reason for it to come off unless one of the pulleys that the belt goes around is bad, check all the pulleys.
How do keep the belt from popping off?
Make sure it's the right belt for the vehicle. Each pulley and ACCESSORY should have grooves that match the belt. Run the engine, make sure nothing is moving around.
also make sure the pulleys are in line
you may need to manipulate the tensioner about another 1/2 turn to increase the pressure on the tensioner spring. If this is set correctly, then you may have a problem on the %26quot;harmonic balancer%26quot;. It could be loose, excessively worn or the mounting spline may have a hairline crack in it allowing vibration to shake the belt off during normal running.
do not over gun the engine


Check if you have bought too long a replacement pulley belt

(the original pulley belt fit the original pulley belt drive just fine, replace if too long)

Check if the pulley belt is twisted before and after you start the engine

(replace if twisted)

Check if the tensioning is done correctly (re-do the tensioning or get a Mechanic)


you have a pulley that is out of alignment with the rest of them. the tension-er is a good start but at this point i do not think that it was bad. perhaps a failing idler is at fault.