Once the case is open, you can flip the motor/pump assembly up and inspect the cylinder to find the air intake---that is, the holes where the air comes ...
INTEX Quick-Fill 12 VDC Electric Air Pump
Single-stage vacuum pumps typically produce vacuum to 35 (mm Hg) or 0.047 , and two-stage pumps can produce vacuum to 25 Torr, assuming air is being pumped and the ring-liquid is water at 15 °C (60 °F) or less. Dry air and 15 °C sealant-water temperature is the standard performance basis, which most manufacturers use for their performance curves.
INTEX Quick-Fill Battery Air Pump.
Gas, often air, is drawn into the pump through an inlet port in the end of the casing. The gas is trapped in the compression chambers formed by the impeller vanes and the liquid ring. The reduction in volume caused by the impeller rotation compresses the gas, which reports to the discharge port in the end of the casing.
Keystone Deluxe 20" Raised Air Mattress with Built In Pump by Airtek
Always use an eccentric reducer at the pump suction when a pipe size transition is required. Put the flat on top when the fluid is coming from below or straight (see next Figure) and the flat on the bottom when the fluid is coming from the top. This will avoid an air pocket at the pump suction and allow air to be evacuated.There is a minimum height to be respected between the free surface of the pump suction tank and the pump suction. If this height is not maintained a vortex will form at the surface and cause air to be entrained in the pump reducing the pump capacity.Avoid pockets or high point where air can accumulate in the discharge piping. An ideal pipe run is one where the piping gradually slopes up from the pump to the outlet. This will ensure that any air in the discharge side of the pump can be evacuated to the outlet.An above-ground pool pump needs to be primed, when it is unable to pump the water through it with force. Hence, when you prime the pump, it means that you restore the water flow. The flow of water is generally blocked because the path has got blocked by a tremendous amount of air. When a pump is primed, the air is purged so that the water can again flow through it efficiently. A few steps have to be followed in order to prime an above-ground pool pump, and sometimes you may experience some difficulty in regaining the prime on the pump. It may be necessary to repeat the steps a number of times before the pump is primed, but without it your pool does not receive quality pool water.