Head swap, a bit slow to fire up?

[Dobbslc]

As the title really, after fitting a new head ( see other posts) the truck now turns over 4/5 times before firing up like is has before when really low on fuel.
It used to start instantly.
I cracked off the injectors on cylinders 1 & 2 as they are easy to reach but not the others, would it still have any air left in the pipes? It runs well after start up so not sure what's going on.
Any ideas?

[Dobbslc]

No ideas? Well it might be something to do with the two virtually flat batteries
Charged it over night and now seems fine!