Pinholes in the floats need to be looked at first since this is at the top of list of unexplained flooding.
Some can hear the fuel inside sloshing around when shaken slowly next to the ear. Others like to plunge them into very hot water and hold them underwater with a wired on stick so as to watch for bubbles of air escaping pinholes or an oil slick as the fuel escapes instead. For the really bad ones just dropping them into water will show very well that they do NOT float high and dry like they ought to but sink with most of the float underwater.
New is short for Never Ever Works. You should still check them.