There are many things that can potentially refer to no or little air intake. I am assuming that when testing it is within saltwater. Skimmers don't work in fresh water. I would start by soaking the pump and venturi (air intake) in a solution of vinegar and water. Then I would dismantle the pump to inspect the impeller for signs of additional buildup, damage or debris. If anything is broken it would require replacing before the pump can become operational.