1994 belt blew apart,replaced tensioner,belt rides off pulley.alighnment looks good.if water pump is bad would this cause this to happen?thanks ,its 318,any help would be welcome.

 

Check the pulleys for broken ribs as well as the belt. Also check for warped pulleys. I've never heard of a bad water pump cause a belt to walk off the pulley. Also you can have someone start the truck while you watch the belt to see how it comes off but be careful as a belt coming off the truck at 600 rpm can be as dangerous and dropping a screwdriver into a moving clutch fan(speaking from experience)

 

will check,thanks.from sussex?im in rhinelander.all seems fine.ive had fan hit my finger breaking in a new cam on 357 chevy motor at 1800 rpms.ouch.

 

You might want to check the width of the alternator pulley. When I replaced the alternator on my 95 with a 5.2 it started tearing up belts. I took it back to Auto Zone and was told there were 2 widths of pulleys called out. He changed the pulley to the wide one and all of that stopped.

 

I see that you replaced the tensioner but that doesn't mean the belt is tight. Check for belt tightness and that the tensioner is actually working and not tightened into a stationary position. If it is working and all the ribs line up, a pulley that's hard to move, or one that wobbles (water pump could do either) could throw it off.

If the original belt was good, something caused it to come off in the first place - I'd look for something not being in line or doesn't stay in line when things are turning. I would take the new belt off and check each pulley to make sure they turn freely and are straight - you'll need to have someone turn the engine over to check out the crank pulley.

 

thanks for info.how much pay should be on belt?i can move tensioner about 1/4 in.seems kinda tight and had a hard time getting belt on.

 

the belt should be able to twist 90 degrees if it twists past that then tighten it if it will not twist to 90 degrees too tight.