A through examination sequence indeed!
Have you tried starting with the EHA unplugged? That condition leaves the acctuator plate in the neutral position, i.e., neither enrichening nor leaning the mixture. There is a possibility that the system controller is sending a full lean (coasting shutoff) signal to the EHA. To build fuel pressure remove the Fuel Pump Relay (FPR) and bridge sockets 7&8 (the FPR contains a timer which shuts off the pump if the engine is not running).