G'day Richard.
I tried rewiring the injector supply. My attempt was unsuccessful as contrary to the alternate wiring diagram, the system cannot work that way. I have since returned the ECU wiring to its original configuration. Both (+) and (-) signal to the Aquamist control module are taken from the injector. With the (+) and (-) signal taken from the injector, the LEDs in the control module no longer illuminate in the pre-crank position.
I understand that once the fuel pump relay de-energises in the pre-crank position the unit senses no power and switches off. I don't understand though why, in the post crank position when the engine is running and power is being supplied to the unit, the gauge doesn't turn on as it did on the first few occasions.