Hi Folks
Just to let you know, whether you wanted me to or not, ZX is now sorted.
If you remember, the priming bulb would not pump up hard; if you clamped the pipe to the injector pump, it did, and kept its pressure.
Replaced all the leak off pipes - they were rock hard - problem solved!
I still haven't figured out why that has fixed it and how the leakoff pipe to the pump is internally connected, and how air gets from there to the fuel.
ZX now proceeding!
Moderator: RichardW