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Discussion and questions related to the course Practical Motorsport Wiring - Club Level
looking for some guidance on building my first harness. I have gone through my service manual along with reverse engineering my existing "cut down" harness. we don't use all of the existing connections mostly the main ecu that runs functions for the signals, lights, fuel pump, and a majority of the relays. actually, the only relay that truly remains would be the starter relay. I have connections that are spliced that don't exactly make sense per the documentation such as the common red on white wire that runs to all 8 fuel injectors that is also spliced into the brown wire that is primarily used for the ignition and the red wire with is my common wire for the 4 coils. also, there is a yellow on white wire that runs into this splice, but the function of this wire was ran into a fuel pump relay nonexistent in the system and an immobilizer that isn't hooked up to anything. I have documented all the pin out wires on the harness initially made based off the pin indicators 1-17 on the top row and 18-34 on the bottom on the 34-pin connector while the 26-pin connector 1-13 on top 14-26 on bottom the documentation isn't clear as how they are identifying each pin out as the first few wires match how I documented them but then seems to be random afterwards. we have a second harness we switched out as we were having issues with this one and I'd like to have one that I know isn't going to leave me sitting in the pits. the harness I've tore down is not exactly as reliable as there are many shotty crimps and corroded solder jobs throughout due to the lack of a properly sealed connection. I know the connections work but if I can remove any extra unnecessary connections to keep the harness neat and orderly that would be stellar. Any help is greatly appreciated.
The documentation & diagrams you speak of... may we see it?
yes, I can send them over I just need to figure how to transfer them from my dad's computer. He has the full-service manual saved onto his computer. sorry for the delay in response I've recently had a change in careers this week, so I've been a tad busy with the transition. I'll get everything posted up by this evening. Thank you for the assist.
Here are the diagrams. I’m hoping that they’re legible I had to take screen shots and I could exactly zoom in all that well on the laptop.
Do you have/able to make a diagram of your current set up, to go along with it?
I can try to make a diagram of my own it might just take me a bit to decipher the splices they have in it currently. I do have a sheet of each pin connection to the 26 and 34 pin ECU connectors. I’ll post a picture of the birds nest everything is just kinda jumbled together. The only nice bundles I have are for the injectors/air pressure sensors and ignition. All the wires that send power or ground the system are a tangled mess.
The first photo is the remaining harness. Second photo is connectors for the injectors and air temp sensor. Third photo is from left to right, the immobilizer, cam position sensor, secondary throttle valve actuator, and the crank position sensor. Fourth photo is the bundle for my ignition connectors the posi-tap wire connector is for our Mychron5 which is how we get a read out for RPMs. Last photos is my sheet of how everything was pinned to the ECU connectors.
Photo of the remaining harness didn’t post. Posting it below
Okay, the brown wire from the ignition switch and spliced into the injectors and coils, is the switch 12v supply to these actuators. For some reason the fuses and ECU relay have been bypassed, so the injectors and coils are directly wired from the ignition switch...not something I would recommend. The immobiliser would have been in the circuit, when it was functioning, to cut power to either the fuel pump or ECU relay.
I would recommend the ignition switch activate a relay that is used to power the ECU and power another relay (or two) for the injector, coils and fuel pump with a fuse in each circuit, as shown in the EFI wiring fundamentals here.
Next you want to confirm all the ECU pin outs, as to where they go, on the correctly functioning harness and confirm their operation. Once this is done, document it and then design your new harness from there.