Make sure you really have got all the air out of the system. I have found that air is often trapped in the fuel filter (thoroughly bleed at the filter head) which then passes into the injector pump even when fuel has previously been bled through.
Also, the lift pump valves may be worn, or have some sediment under them (there is a screen filter in the pump) which results in some air being sucked back and forth.
Have you got the injector pipes disconnected from the injectors? I find this is usually necessary, then crank engine until fuel shows. It does not come out at high full bore pressure.
If everything appears ok, resort to cranking the engine and applying a little Easystart. If you can run the engine with this for a few seconds it may be enough to get the fuel through.
I have spent many happy hours doing the same thing!
Mr. Toad
July 2008