Put the pump in some diesel and power it(run longer wires to the pump to prevent shorting near the fuel…or it could explode..and use diesel it will be contaminated if waters used..)with the output to another bucket…if it moves lots it’s good, if its really slow its shot…
And the fuel pipe is possibly blocked…some compressed air may fix that..
If there is any doubts replace the pump and pipes and fuel filter and purge the system at the high pressure pump( a hand primer and some stamina should be enough) until solid fuel is present at the high pressure pump ..then try to start(if needed some light brake cleaner can help but little amounts as it can backfire badly..