With the fuel lines run it was time to pull some wires. First step is the main harness through the body. I am running a Microsquirt ECU. These have more than enough features to control spark and fuel on an old 911 and the package is small enough to fit inside the tunnel under the shift coupler.
The wiring harness is pulled through the speedo cable hole. There is room for both the speedo cable and harness. From the tunnel exit the harness routes up across the DS undercarriage following the same basic path as the fuel lines. The wiring enters the engine bay at the DS rear corner behind the shock mount.
At first the bundle of wires is daunting... So many colors.
The wires are all clearly marked and get divided into 3 categories.
1) unused - Which means they get cut off and secured out of the way.
2) car side connection - these are 12V, ground, O2 sensor and ignition outputs.
3) engine side connections - these are all the engine mounted sensors and injector connectors.
I separate the engine side connectors with Deutsche 12 pin connectors. Waterproof, easy to install and gives single disconnect point for all EFI should I need to drop the engine.
The main connector is the focal point for the engine wiring harness. You can see here some of the different directions electrons must go. I leave the wires out until it is time to secure and cover.
Based on the position of the 12 pin connector, I use a CAD (Cardboard Aided Design) layout for my wiring harnesses. Simple really. Binder clips in injector and sensor locations. I can clip a connector, cut a wire to length, crimp a terminal and assemble the proper connector with heatshrink as needed. And... I can work in an Airconditioned space. This is most important in July in TX. I think my wife is amazing considering she will walk out in the morning to find wires and tools all over the kitchen floor. Love her for sure...
The EFI needs ignition control. I am a fan of big spark. If there is ever a fault in the EFI you need plenty of spark to keep it going. Case in point... Years ago my MAP sensor failed one a drive. I was 2 hours from home. The car thought it was at WOT all the time. This meant I was running AFR7 under cruise. The twin plug driven by dual Crane Hi-6 boxes never fouled a plug as I drove home. Yeah, I put them back into this car. I mounted them clean on the backside of the rear deck.
A few other items were added. I run a secondary relay and fuse panel in place of the stock CDI unit. I also mount the wideband O2 controller in the same location.
Once everything was mounted I was able to go back and tie up the wiring harness.
The engine bay is getting more busy but it certainly stayed as clean as possible.