I have now traced the wire that renders my fuel pump powerless. The wire runs from the ECU to the fuel pump relay. It must carry a - charge in order to work the pump. But unfortunately, it is not giving out power so I am suspecting the ECU to be the culprit. I do not know how I can resolve this problem? Can the ECU be repaired?
ECUs are not easily repaired. You may wish to replace it with one from the junkyard. This will also confirm your diagnosis without the cost of a brand new ECU.
Also, on cars this age, make sure to test the entire electrical circuit. Your little wire may not giving the power it is supposed to because of:
- bad connections
- bad relay
- bad fuse
- bad ground
ECUs can be sent off for testing and repair. Here in the UK testing is usually £30-50 and repair is around £200. Search for ECU testing and repair in your area.
Although if you are good at electronics / soldering and are sure the ECU is at fault you can open the ECU and follow the PCB trace to work out what components control the relay, usually a fault like this is caused by a faulty Mosfet which is a 3 pin device.
If you purchase a second hand ECU it may need to be programmed, some will require physically swapping a chip, some may just need the keys programming.
There is also a possibly that the ECU is not at fault. Are you sure the ECU is meant to supply a live? Most ECUs switch the Ground of relays and the Live would be supplied from the fuse box.
There could also be a fault that the ECU is being told not to switch the pump on, for example an immobiliser fault, or a missing live or ground to the ECU. In this case a code read and then checking each wire against a pinout would rule this out.