There's another fuel filter just at the connection to the Fuel distributor.
Make sure this is not blocked.


If you pressurize the fuel system - turn the ignition key to on - then slightly loosen each injector line at the fuel distributor one by one - fuel should come out.

Next step would be to completely remove the Air mixture unit and clean it. Make sure that the plunger from the fuel distributor is not jammed up.

Make sure the air plate is not jammed up.