It is silicone grease. Available at pool stores and probably other places. Kind of expensive but a < $10 tube will last a long time. Don't use any petroleum based grease as that will attack the gaskets. Just to add to what Carl said, even a tiny air leak can cause havoc and prevent priming and even suction. Try clesaning and lubing the gaskets and see if that helps. If it doesn't come on back and we'll work on it more.
Al