Airlock

Ive got an airlock on my 79 deisel but i cant find the bleed screw.
Its got the filter housing with the plunger on top but not the same one as in the handbook.
Also, would an airlock cause it to be difficult to start and erratic when started then cuts out after 5-10 secs, or do i need to start looking for a blockage elsewhere?
Any help is much appreciated.

thanks Nafe.