Big question if your new to Rover's...
If we ignore all the frilly bits like lights, wipers and indicators there are three essential items to ensure the K series engine starts, four if you include the key FOB.
The engine wiring loom the ECU, the AS5 are essential and if you want to pass an IVA a dashboard/rev counter/speedo pod will be needed. A lot of the POD warning lights are fed from the ECU.
So you are sure why, at the request of the ECU the AS5 sends a serial digital signal back to the ECU, (this is not a DC on/off but a serial communication link), that is unique to the pair, without this unique returned signal the ECU stops the fuel pump operating.
The effect is the ECU runs the pump at switch on, checks with the AS5, if the AS5 fails to respond correctly the engine starts but stops after a short while as there is no fuel pressure.
The immobiliser FOB is also linked into the ECU so if its set to 'auto immobilise' you need the FOB to work as well, the ignition switch will not do that.
The ECU, FOB's and AS5 can all be reprogrammed to work together Technozen can assist there, if its all messed up or different car provided items.
I guess your ECU is the single black socket with less functionality than the dual socket ECU but the principles are the same just different circuit diagrams.
For my VVC 1800 I did just what you are heading into, I used the provided 'frilly bits loom' and stripped the Rover loom down to match my needs. Once you understand the AS5 and ECU needs the minimum of wires to start the engine; plus what you want to be retained as functionallity, your heading inthe right direction.
You need to decide what you want in the new set-up and remake those connection, some circuits need to be shorted out on the AS5 to maintain the engine working systems.
For instance I retained the drivers door lock, this enabled me to access the test mode of the AS5, not much in itself but it also enabled me to override the immobilise if the FOB stops working. I also retained the Rover POD and made all the warning lights work and retained the option for ABS if I choose to, in the future.
Perhaps your first problem is to understand the capability of the Rover ECU, AS5 combination and then select the circuits you wish to retain, then you will know the wires you need to remake.
This SWISSONLINE web site may make your life easier once you decide what you want to retain. This shows the two socket ECU wiring where as yours may be the single socket.
http://homepage.swissonline.ch/TomsS...tion2/Map.htm#
I have the dual socket diagrams, circuits and write-ups if you have difficulty researching them on the net. I only have the Rover manual for the single socket.
Hope this helps a little, it took me 6 months to research, strip and rebuid the loom for my Marlin and I had the provided loom from Marlin as a starter to 10.
regards
eaa53