Power steering pulley install

'95 S10 Blazer 4x4 LT 4dr "W" code 4.3L 100,000 miles

I had the serpentine belt come off. Found that the power steering pulley had worked its way off the shaft causing the belt to roll off the pulley. Put the pulley back to flush with the shaft, ran fine for 20 minutes, then the belt was off again and the pulley was loose. (about 1/2" from flush)

Is there supposed to be a bolt in the end of the shaft to hold the pulley on? Or is this just for the pulley puller tool?

If no bolt, has the power steering pulley worn where it will not seat? Or does the shaft wear out first?

No bolt on the end.
But there threads in the pump shaft for the install tool that installs the pulley.
The pulleys are a press on fit on the pump shaft.
Which is tight and takes a tool to remove or install it.

Could be either one or both worn if it has slipped and come off.

You could try your old pulley on a new or rebuilt pump and if it has to be pressed on with tool install tool that comes with rebuilt pump and is good and tight and has to be removed with the remove tool/puller .
Then pulley is good but if not press fit tight on a new pump then find another pulley.
You could also try your new pulley on the old pump and see if it is a press fit on and off.
If so than a new pulley will do it.

Or to save the check out hassel and be on the safe side replace the pulley and pump.

Good Luck
MT