I don't know about the valving for suction but I had the impression that pulleys were easily damaged and then prone to failure. Are you using a pulley puller for removing and installing the pulleys? Did the first one break after changing the pump?

Also heard of mismatching belts and pulleys. Seven groove, eight groove? But that kills belts, not pulleys?

Probably the powerstroke forum would be a better place to ask.

 

hey did you ever figure out why it keeps breaking? I am now on my 4th vacuum pump pulley!

 

Can you spin it by hand with the belt off? One post after 10 years????? Sandy

 

yes, took the belt off and can spin the shaft of the pump by hand

 

I had to replace my pump because it was binding. I could hear it grinding when driving (at different times). Hear anything like that??? Other than that I can't imagine why the pulley is breaking unless something is misaligned. Have you changed anything else that is driven by the belt?

 

Yes, when the original pulley broke at 350k miles I replaced the idler and belt tensioner from the Ford house. And installed a new doorman vacuum pump.

 

The idler is not on the same belt as the pulley on my 91. I ran a shorter belt and bypassed by removing the pump pulley for a long time until I decided to replace the pump. My pump belt only runs the pump and Alternator and fan. Belt tension is done on the alternator.

 

Sorry I glanced at you title and now see it is a 7.3. Sorry about that. Sandy