if surging you mean the paint blasts out then stops then blasts out you have a ail leak somewhere. probably in the gasket between the fluid tip and the body of the gun. remove the tip lube the gasket then re tighten.
if that doesn't solve the problem the needle packing's are leaking air. this is where the needle enters the spray gun body. there will be a nut there. remove the nut, lube the gaskets inside of the nut, they might be on the in the body of the gun also, and re tighten. tighten the nuts pulling the trigger when tightening, do this until the needle starts to stop returning into the gun, then slightly loosen.
use spray gun oil when lubing. if you don't have spray gun oil use vegetable oil. DON'T use air tool oil. this can give you fish eyes.