OPEL ASTRA G 1.4L 09353459 Delco Multec S DHZJ fuel pump relay, main engine relay

[Nik Matsa]

I have an ecu 09353459 Delco Multec S DHZJ. Car starts some times cold and after maximum half an hour working fine car doesn't starts again.
Diagnosis gives me faults on main engine relay, fuel pump relay and thortle position sensor.
I have checked the ecu well for the common soldering problems (aluminium wires plugs).
I have changed the relays.
I have checked wiring for relays, ecu plugs, fuel pump.
Problem remains.
I have tried a spare used ecu, same problems plus spare ecu gives one fault more ignition coil. Spare used ecu as I checked has problem in the ignition coil which i get fault, but I still have faults on fuel pump and main engine relays. Maybe used ecu faulty too, but this coincidence of same faults makes me believe that there is not a problem on ecu.
Now I am searching for a second spare ecu to test if both ecus tested so far where faulty
Anyone has suggestions on what is happening?

[super jumbe]

Had one last week with similar issue fitted new ECU got it sorted, info you provided looks like 99% ECU Delco Multec they have issue.

[Nik Matsa]

maybe aluminium wires soldered to mcu or to other IC are the problem. They are so thin you can't check them. What do you use for aluminium soldering? I use cooper wires and scrab well contacts on pcb. I saw some videos using ultrasonic soldering iron and some videos using some special flux. I want to test the flux, the ultrasonic soldering in videos makes sloppy soldering.

[cubica1]

simple cooper wire, simple soldering iron, simple flux...no need anything especially! This pump problem is only beginning...it's need to check all wires into ECU. Your spare ECU is in faulty, too, unfortunately. Need to be repaired, also.
regards,
cuby