Could you have crossed the wires when connecting the new pump? Did you plug the hoses or clamp the hoses when doing the install?...if plugged, maybe something is in the hose obstructing the flow?(I am speaking from experience!). Can use a bucket of water to test to see if it is pumping water. I thought if you rev the motor over 2000 rpm while in park the pump will turn on?

Sensor is another idea - inexpensive and easy to do.