bubble thats air
main fuel pipes should full bore when pumped
inj pipes should spurt when engine cranked
you dont want air bubbles going to the pump or you have to start all over again
whats wrong with the new fuel pipes different size/material if rubber have they reacted to the diesel if the cheep white plastic braided hose they go soft with heat and hard with cold both not good
are you sure you know what you are doing?
all posibilities have to be eliminated
ye they will rebuild your inj pump even if it is not needing it as long as you have the money to gift them