Check to see if the "O" ring is still in place on the filter. Insure the old one came out.
If the "O" ring is pinched, damaged, or gaped open away from its sealing surface the pump may be just sucking air instead of fluid.
Below is a picture from "Prodemand".
Keep us posted as to what you find.
Sunday, November 25th, 2018 AT 8:30 PM