1999 Polaris SLH, SLTH, SLX, SLTX, PRO785 Factory Service Manual, Page 131Get this manual
FUEL SYSTEMCARBURETION Fuel Tank Check Valve Testing Fuel Tank Check Valve Testing
To test the air inlet che'tk valve,remove the valve and apply approximately PSI pressure to the end of the valve marked "vAC"The valve should hold steady pressureConnect the tester to the other end and apply pressureAir should pass through the valve with no pressure build upReplace the check valve if it holds pressure both ways or fails to hold pressure one way