The 6.354 Perkins Engine depending on how old it is?Are hard to start when cold under 40 f / 5c
But if the unit is not old and worn out they do start fine.
We have installed block heaters in them then they start easy.
On both your diesel engines as long as the filters are good and there are no air leaks so the Diesel drains out. You should not have to bleed them.
It sounds like you have a leak at one of the filters or Banjo line fittings.
The hand Prime pump is just when you change filters.
On Some of the Perkins 6.354 we also have installed Electric charge pumps then bleeding when the drivers run them out of diesel is easy.
Jeff