First of all, if you have no pressure, you are correct.......the problem is in the suction side of your system. Next, since you have apparently checked the entire suction route and don't see any clogs, then I would suspect a suction side leak......very possibly around that crack. If it's not clogged, (and it sounds like it's not) then air is getting into the system somewhere between the vacuum head and the impellor on the pump.

Hose connections tight? Water high enough in pool not to let air in skimmer? Crack in pump basket fixed?