The big rule: route now, power later
When you lay out the output side of the loom, take every power and ground wire to the place it will eventually connect, but don't connect it yet. Finishing the routing first lets you check every run while nothing can be energized by mistake. It's also how you avoid a coil or injector being switched on before the ECU has been configured.
A sensible order for output wiring
- Injectors. Take the injector wires in the loom to each injector. Each injector gets switched +12V on one pin. The ECU's injector output wire connects to the other pin and provides the ground that opens it. Label each wire by cylinder as you go.
- Fuel pump. Connect the pump back to the fuel pump relay. The ECU runs the relay and the relay carries the pump's current. See fuel pump wiring.
- Ignition outputs. Route the loom from each ignition output to the ignition module (also called an ignitor or spark amplifier), but leave the modules unplugged for now.
- Coils. Connect the ignition modules to the coils, and run the coil power supply back to its relay.
- Idle control. If the engine has an idle valve or motor, connect it now.
- Auxiliary devices. Finish with anything else driven by an output, like thermo fans or a boost control solenoid.
Until the ignition output settings are correct for your modules and coils, an output can hold a coil on and overheat it, or fire at the wrong time. We leave the modules disconnected until the ECU is configured and the outputs are tested. Follow the warning at the start of the Elite manual on this.
Checks before you power up
- Every injector has a common 12V feed and its own ECU output.
- Relay coils go to ECU outputs, and heavy current goes through the relay contacts, not the ECU.
- Output wires are clear of hot or moving parts and away from ignition leads.
- Nothing is powered until the ground and power wiring is complete and checked.
Next, finish the input side with the inputs summary, then do power and ground wiring last. For physical placement of the ECU and modules, see mounting devices.
