Cummins 3.3 VP 44 injection pump in Vermeer chipper

My chipper will start and immediatly stall and I am not sure why I bought it this way. I have changed fuel filter and electric fuel pump. I have good fuel flow to the pump inlet and also out the top of the pump to return. I have also removed the shut off plunger. Any other suggestions before having pump rebuilt?

Cummins 3.3 VP 44 injection pump in Vermeer chipper