Westfield Megabusa Build Diary

07 Mar 2008
ECU wiring continued

Mark sent me through a document detailing the complete list of modifications that must be carried out to the ECU loom, as well as instructions on what to connect where once the modifications have been made. I wouldn't have been able to do it without this document.

The first thing to do was connect the power cables up to the engine. The chain is very simple.

  1. Take the longest power cable, and connect it from the positive battery terminal to the starter solenoid (it has a plastic cover over the terminals). Connect this to the left terminal. You will need to run the power cable up through the panel where the fuse box lives, as the starter solenoid should fit on the ECU tray.
  2. From the right side terminal on the starter solenoid, route this back down through the panel, into the engine bay, and connect it to the starter motor.
  3. Now connect the starter solenoid to the negative battery terminal.

With this all taken care of, I decided to try and engage the starter by turning the key, but nothing happens. I trace through the wiring and I find out that in order to start the car, the engine must be in neutral, but I'm not getting anything from the gear position sensor.

I was playing around for ages, and I eventually find that the signal into the starter solenoid from the ignition barrel was not connected, so I manually connected the white/red cable from the Westfield loom (starter signal) to the yellow/green on the hayabusa loom. This tells the starter solenoid that the key has been turned to start the engine.

Now when I turned the key I got a massive drain on the battery (I could see it on the multimeter), but still no action. I tested various circuits, but still couldn't find out why the signal is not reaching the ECU loom from the gear position sensor etc.

I checked that the starter motor was working by touching a live cable straight from the battery to the starter motor, and it immediately whirred, so I know it works.

Eventually I work out it's because I have not earthed the ECU loom which was really silly. I removed one of the screws that holds the ECU tray into place, and secured the black/white earth wire here which keeps things very near, and saves running a cable back into the engine bay.

Now a quick turn of the key and the starter clicked into life. Apparently it is safe to do this as long as it's only very quick. There was no oil in the car though, so I did it once and left it. Now we know the ignition circuit is working, so we won't have to play about with wiring next time, except for making a permanent connection between the white/red and yellow/green wires for the starter signal. I'll also have to connect up the RPM signal, gear signal, and fuel pump etc. but I'll do this properly next time.