it's a 2005 P6000 with a diesel 4 cylinder S/N AT14E00844, it seems like it's losing prime, if I prime it with the plunger it will get hard but within a min it gets soft again, Most of the time if I prime it it will start right up within a couple revolutions of the motor. I blocked of the line coming from the tank like a check valve but still gets soft, If i block off the line going to the injection pump it will stay primed. I've replaced the filter, housing due to the diaphragm being torn, lines going to and from the housing. It also seems to start better when it's ran for a bit. Just wondering where I could be losing prime or why it cranks so long when cold, it's inside a heated shop. Glow plugs seem to working and tested ok and getting voltage to all of them