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  • Wiring Harness Questions

    Howdy, I'm a new member here. I'm from NPORA so a few of you may recognize me, I recognized a few of you. I've been using this site as a reference for a lot of my Z31-Pathfinder swap. I spun a rod bearing in my 5-speed manual '88 Pathfinder at 194K and swapped in a motor from an automatic '84 N/A that has only 102K on it. I kept the TBI set up for now, with plans to eventually swap the entire Z31 intake and MPFI set up in. I noticed when I was pulling the wiring harness from the Z that there's a long white plug attached to it, but doesn't go into the computer it's self. I was wondering what it was? Extended wiring for the engine to run? I've done essentially nothing but confuse myself with the wiring diagrams (I'm NOT good with wiring, and staring at a mess of a harness is a little intimidating).

    If y'all could give me a heads up on what to do with this I'd appreciate it, I want to try and get this mess done with by Tuesday. Likely not to happen, but it's worth a shot. I'm tired of the TBI giving me issues...
    Thanks in advance!

    The plug I'm questioning.


    The mess on my garage floor.

  • #2
    Anyone?

    Comment


    • #3
      In a Z31that plug plugs into the main body harness right above the ecu. Your going to have to look in the fsm to figure out what those wires are for. What yearZ did it come from and was auto or manual? You also may need to know what trim the car had. GL,GLL,ect.
      FSM's can be found here. http://xenonz31.com/reference.html


      At a quick glance at the 87 fsm efec-13 The plug is for your guages and the like.
      Hope this helps.

      Comment


      • #4
        Thanks for the info and link! It came out of an '84 automatic, I'm not familiar with trim levels however. All I know is it didn't have an electronic dash, but had rear seats, climate control, power seats, etc. I also have another question I thought of about the O2 sensor. The Pathfinder uses a 3-wire heated sensor with an extra ground, and I've read that the Z cars can use two different types and that one won't work with the other. I'm wondering if the Z computer will accept the oxygen sensor that's already in my truck, or if I'll have to change it out? Thanks again...

        Comment


        • #5
          motor is 84 auto with analog gauges. (turbo or non-turbo?) Seats and accessories won't affect the parts of the harness that concern you.

          The auto harness will have a few extra wires and an extra sensor on the throttle body next to the TPS that you can eliminate/ignore. (it deals with the auto trans shift signal)

          FSM will give you diagrams one sensor at a time. Wire colors and functions stay the same 99% across all years and trim levels on vital engine sensors but their pin locations may change slightly.

          Are you intending to keep all of the emissions components intact?

          The engine harness will have 4 connectors under the Z31 dash, 2 on each side, one goes to the dash harness the other into the chassis harness. The only vital stuff that goes through these is your ignition coil/power transistor signal to the tachometer and the fuel pump circuit. If all you have is a bundled up engine harness the easiest way to identify what plug you're holding is the wire colors and pin locations compared to the diagrams.

          I understand what you mean about the intimidation factor of the project as a whole. If you take the time to go through the FSM one section at a time and identify each individual sensor/component and then familiarize yourself with the diagram and where those particular wires are within your harness it all starts to fall in place.

          Do not be afraid to cut up your harness. The easiest way to keep things neat and organized is to do just that. LABEL EVERYTHING as you go along. Determine where you will locate the ECU and other items inside your vehicle before re-soldering everything together. Solder and heat shrink is a must.

          reference your o2 sensor part # against the appropriate part # for an 84 Z31

          I have some diagrams in my build thread that you can refer to but a lot of the FSM diagrams cannot be simplified further so I didn't see the need to re-do them.
          http://www.z31performance.com/forum/...6371&start=144

          I wrap my paper weights in glitter.

          Comment


          • #6
            Thanks so much for the reply. The motor is a non-turbo. I did notice that the O2 sensors are different, the Pathfinder uses a Titania unit I believe. It's 17MM, with 3 wires to a connector in the engine compartment and 1 extra ground plug. The plug from the Z looks much different, but I think for ease I will just weld in another bung and use the Z sensor.

            I am not keeping any emissions stuff, besides the sensor since it really affects performance and fuel mileage.

            I downloaded an '84 FSM and started tracing wires, and printed off the diagrams in the pinned topic that already has the connector all labeled up which is a big help. I still need to figure out what wires on the Pathfinder I need to splice into the Z harness, but I can't find a TBI specific wiring diagram anywhere on line. Every one I've found or that people have sent me have been for a MPFI '90+ Pathfinder.

            Since that white plug doesn't plug into the ECU it's self I'm wondering if I can get away with removing it entirely and running the wires I need to the pins on the ECU. I noticed quite a few wires from the white plug do a U-turn and head back into the ECU and some don't. I'm assuming those wires are the coil/ignition system and the fuel pump.

            "The only vital stuff that goes through these is your ignition coil/power transistor signal to the tachometer and the fuel pump circuit." Is that what you're referring to? The white plug?

            The ECU will be mounted behind the glove box, since the wires aren't long enough to go to the stock location which is under the passenger seat. This works out well since it moves the computer away from the floor boards so it doesn't somehow get wet. It kills 2 birds with 1 stone. :-D

            Thanks again.

            Comment


            • #7
              o2- use proper part# for your Z31 ECU and wire according to Z31 FSM.

              Deleting emissions stuff makes wiring much simpler. In the FSM EL section where each sensor has it's own individual diagram some are labeled as self diagnosis check engine light items. Keep these wired up. Delete everything else.

              in reference to "that white plug" I'm going off memory here. The 4 plug connectors that connect the Z engine harness into the Z, 2 on each side of the dash, I think the white ones go to the chassis harness and the blue go into the dash harness. Don't worry about how it is or was in the Z. If you follow the diagram and understand it's function just build to suit. By comparing the plug/pin/connector diagrams to the actual connector you can identify what is what by wire color and wire locations on the plug. Also, the FSM labels each connector with a letter/number abbreviation so they can be more easily labeled in other diagrams that show their location in the vehicle.

              TBI diagram might not be necessary so long as you can locate tach and fuel wiring in your chassis harness. If not then just wire it up from scratch. The only other items that would be connected/spliced from your chassis harness into the Z engine harness are power/ground sources for the ecu.


              As you go through the harness and identify/modify each individual wire take the time to inspect the full length of the wire for any kind of damage. Replace as needed, even if it appears ok but the sheeth is dry/rigid.

              I wrap my paper weights in glitter.

              Comment


              • #8
                Good deal. I located the all the wires I think I need to connect to the Z computer according to the "required to run" part of the wiring diagram on this site. I included the idle up wiring for the heater, lights, turning, and what not just because. I'm going to assume the neutral switch is a null point.

                Pathfinder pins...
                Fuel pump: Pin 108 (white/red)
                Load signal: Pin 22 (gray)
                ECU power source: Pins 27, 35 (green and green)
                Ignition signal wires - Resistor: Pin 3, Transistor: Pin 5, Transistor: Pin 14 (white, gray or white, white or blue/white)
                Neutral switch: Pin 10 (doesn't say)
                Ignition switch: Pin 9 (black/yellow)
                Main relay: Pin 6 (blue/red)

                I noticed that two of the three wires for the coil, coming from the Z computer, are the same color - green with red rings. What's the difference between the two? The other is blue with red rings. I would *assume* that the blue/red would be connected to my Pathfinder's resistor pin 3 since they are both the standalone wires from the computers. I also need to figure out the difference between my Pathfinder's ECU power wires, since both are green and go to the same damn thing in the diagram.

                I'd hate to mix two of the same colored wires up and create a smoke show...

                On the Pathfinder, the tach is linked to the coil resistor wire so I think it's all ran through the chassis and not really something I need to link between computers, as it should come along with the other coil wiring I need to do.

                Comment


                • #9
                  I don't have the FSM with me at the moment but this is how I wired my coil and power transistor.

                  have you traced those 2 green wires full length? do they fuse/branch off each other any where?

                  off memory...
                  Pathfinder pins...
                  Fuel pump: Pin 108 (white/red)---(is this the power source from ECU to fuel pump?)
                  Load signal: Pin 22 (gray) ---(TPS or something else?)
                  ECU power source: Pins 27, 35 (green and green)
                  Ignition signal wires -
                  Resistor: Pin 3,
                  Transistor: Pin 5,
                  Transistor: Pin 14 (white, gray or white, white or blue/white)
                  Neutral switch: Pin 10 (doesn't say)
                  Ignition switch: Pin 9 (black/yellow)---(ignition/egine start signal to ecu)
                  Main relay: Pin 6 (blue/red)---(injector power source)

                  power wires are the same. they originate from the same point, split, and carry power to separate parts of the ECU. any/either wire should be fine on any pin location of the ECU

                  "link between computers" ???

                  what are you trying to link and why? This should be a remove/replace kind of deal. Rip out TBI, wire in Z31 EFI harness. Am I misunderstanding something?

                  I wrap my paper weights in glitter.

                  Comment


                  • #10
                    My plan is to retain some of the TBI wiring related to the chassis. The coil, tach, temperature gauge, and fuel pump wiring, and get rid of the rest. I didn't notice any plugs for the Pathfinder coil that I could just plug into the Z31 wiring harness, which is why I'll need to splice the Z31 coil and power wires to the wires on the chassis for the Pathfinder coil if that makes sense. I have yet to trace the green wires for the ECU power fully, it's been pouring like mad outside and I need to move the truck in to the garage. I've been moving it around as needed with the starter, and I have a spare one in case doing that burns it up.

                    Pin 108, the fuel pump, goes directly to the fuel pump relay in the relay box under the hood. That part is simple, swap the Z31 fuel pump signal wire to that and be done. Pin 9, the ignition signal wire is the same way. Swap wires and be done.

                    It's mainly the transistor wiring that's getting me. I have a pretty hard time relating things on paper to the physical wires. I'm a kinesthetic learner and usually have to have my hands on things to really understand them. However when talking to someone who re-routed the entire coil system on their Pathfinder, he said the black wire is + and the blue-ish wire is - for the transistor.

                    Comment


                    • #11
                      Ok, sounds like you are on the right track.

                      I am the same type of learner. That is why I recommended going through every wire and unbundling everything so you can see what the diagrams represent.

                      Do you have the diagrams for the pathy chassis harness? Trace them and replicate the z31 diagram. If not just add new wires for the z31 coil.

                      I wrap my paper weights in glitter.

                      Comment


                      • #12
                        I do have the full diagrams for the Pathfinder, engine and chassis copied from Mitchell manuals. It's helpful to say the least. If it does become too much trouble to run the Pathfinder coil, transistor, and resistor I'll install the Z coil. I can't see it being that big of an issue though since they run off the same basic principles.

                        Comment


                        • #13
                          Well I'll be damned, it fits.





                          Comment


                          • #14
                            Alright, I've got a few more questions. I've got the entire intake in and fitted, I tried a test start but it just cranked and cranked. I did notice I had crossed a few wrong wires, so just in case I put in a new computer. The fuel pump won't come on with the Z31 computer, but comes on fine with the TBI computer. Both use pins 108. Now, pin 20 or "fuel pump relay" was said to be not needed for the engine to run. Is it? What does it really do? Pin 115 is shown to go to the "pressure regulator control modulator" and the O2 sensor on a wiring diagram, but this link: viewtopic.php?f=6&t=6182 says it's a ground. Uh? I'm also not getting spark, with 2 different coils and transistors, yet the Pathfinder and Z31 ignition wiring, CAPS included, is identical.

                            I've gone through and removed all of the pins that are unused to make less confusion.

                            Oh, then if put the positive lead from a Fluke meter to the 12V out for the injectors and ground the other lead, the fuel pump relay clicks and the pump comes on but never shuts off.

                            I'm fuckin' confused!

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