mounting an electric pump

ALL pumps "would rather" push than "suck." The more precision the pump impeller, the more suction it generates, (inlet vacuum) but the more fussy it is with regards to wear and debri in the liquid being pumped.

On the "loose" side is an automotive water pump, which generates nearly NO suction.

It might be interesting, but not practical, to "rig" an automotive pump in such a way that you can measure the lift, similar to a shallow well pump. I bet it would not be much

On the "far side" something like a refrigeration compressor can "pump down" into some pretty fair vacuum readings. Of course they don't like pumping liquids AT ALL