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Hi I'm Ross, thanks for trusting me to help you today. I am a diagnostic and repair technician and I look forward to working with you.
This sounds like a problem with the ECU, Have you carried out a diagnostic scan yet to see if there is anything obvious stored in the memory?
Ok great. The ECU is fed from the fuel pump relay but it also has its own power supply.An earth problem is perfectly possible so I would advise checking the ECU Earths, and coil pack.I have seen ECU Failure occur from powering the ECU with certain connectors disconnected, certain earth feeds can cause the power to back feed through the ECU Components and cause them to burn out. The fuel pump will not run without a feed from the ECU, so keep that in mind, the coil pack amplifier can also burn out with its earth disconnected which is a possibility.Its going to be difficult for me to give you specific advice as to what it might be and other than ECU failure caused by powering it with various circuits disconnected, there is a good chance this is something very simple such as a bad ground etc... I think you will need to have a good probe about with a mutimeter at the relays, switching and switched sides, also check the ECU power supply from the relay at the ECU connector if not already done. Do an EOBD scan ASAP And let me know what if anything is found as this may offer a clue.I'm attaching some diagrams of the ECU wiring which is not great but will give you a rough idea of how the circuits and relays work.
No problem, just reply when you are ready and I will get back to you ASAP. Feel free to ask if you need any assistance in the mean time, thanks, Ross.