Opel Vectra-A 1993 C18NZ Not Priming

Hi guys,
I have one problem with this car, the car is Vectra-A 1993 1.8 petrol, pretty old car but the problem is quite interesting. The car is not priming, meaning when you turn the key to the ignition on the fuel pump is not priming, you can not hear the fuel pump working. Tested fuel pump relay which is ok, fuel pump is ok, power to the relay is ok, power through the relay to the pump is ok, wiring to the pump is ok, fuses are ok, all power wires to the ecu are ok, all grounds to the ecu are ok, the ecu doesn't grounding relay in priming phase but grounding works fine when you turn the key to start position and car will start fine in most cases. I swap good know ecu and the problem is still here meaning something is wrong with wiring. Do you know where to look for this culprit? Do you know what generates the grounding signal and how this work, why ecu is not giving a ground to the relay in priming phase? What may cause this? I am pretty sure that must be something with power to the ecu or ground to the ecu but this is tested and everything is fine. I can bypass this malfunction but i would like to find a cause of this problem.
Thanks.