Sam, this may or may not be the case, but sometimes the simplest answer is the right one --- try turning the vac hose around (switch the end in the skimmer and the end on the vac head. Many of the vac hoses have a swivel cuff on the end that attaches to the vac head, if you connect that end in the skimmer, it can suck air and momentarily kill the prime (ther swivel end isn't air nor water tight).