I have a spare fuel pump for use in emergency,i tested it today by shorting it out across a good battery and it did not run but just made a clonking sound, do these fuel pumps only run when they are primed with fuel ?
The pump has 4 blades that are thrown out from the hub of the motor. If a blade is sticky it may jam as you have found. As said run it backwards but first give it a squirt of WD-40 in both ends.
