3 point not working

[RCHamblin]

I have a 72 Ford 2000. The 3 point don't work until I prime the pump by blowing air into the housing. I need to prime everytime I use it. Sounds like a check valav to me but which one? Anyone have any ideas?

 

[Egon]

Any filters or screens on the suction lines?

 

[davesl708]

Is the vent plugged?