John/Jads, seems you have found relays and still have issues relating to identifying which of the two is controlling the fuel pump...? I know next to nothing about ECU`s used in cars or the theory behind switching earths as opposed to the the live, but if all the earths are black as was the norm pre ECU, then I can understand you may not be able to follow the more usual method of identifying individual switched circuits by using the colour code of the wires...? Which may have from the following link been a white wire with a purple tracer..?
http://www.mgb-stuff.org.uk/colourcodes.htm#:~:text=In%20the%20United%20Kingdom%20the%20British%20Standard%20BS-AU7,a%20thin%20line%20trace%20of%20a%20different%20colour.
I am also interested to know why you want to fit a relay with a Diode...Is the diode to quench the spark across the relay contacts......? Or is the diode across the relay`s coil connections, to suppress the coils back EMF when it is in the process of de-energising ( switching off) to avoid upsetting the ECU internals...?
