Pump continue to prime when vacuum is on?

[tyesman]

Only when the vacuum is ON, it continue to prime. When I switch to FULL skimmer on the valve port there is no prime and everything works like it should.. Now i do get good vacuum suction on the vacuum head but it runs pretty slow. Usually my Hayward would climb up the walls.. NOW, it wont go up the slop to 3 feet. I've try letting it vacuum for hrs to make sure it might suck up whats MIGHT be stuck in there. I have notice recently and remeber vaguely, there is this port located on the deck. This thing looks like the thing in the tolite restroom. usually it makes a hissling (SSSSSS) noise. now nothing. I even un screw it and nothing happens. can this be the issue???? Some info that may help, its a 33k gal pool, cartlige filter at 8 psi and clean out. water is balance perfectly for the past 2 weeks, last 2 weeks ago i drain and did a chlorine wash.. Before the wash it was still having problems. I remeber seeing 2 sheets of small napkins when the vacuum was running. The vacuum head is a new head i got for free and still pump still primes. I have another head in working condition that I switch to test. no results there. I have new vacuum lines and clean out all lines.. MY question is HELP HELP HELP???

[tyesman]

need some help guys

[tyesman]

???