Hey guys Im nearly done with my jspec s4 T2-usdm s4 T2- swap and I had a couple questions about the sub harness and connectors. this is on my 87.

1st question- What purpose does this wire serve? looks like a major engine ground to me? where does it connect to? is this for the negative battery cable?


2nd Question- is this electronic component ok being mounted here?


right now when I connect my battery terminals I hear a pop from the ground or starter area like something is shorting and im getting no power inside the car.. hoping I havent damaged anything.

 

The large wire is for the starter ground. Attach it to one of 2 bolts.
The small black box is a capacitor for the oil pressure sender. Attach that to the clutch slave bolt.

 

Thank you for the advice man! I'm not sure which bolt you speak of when you say "Attach it to one of 2 bolts" though. you mean one of the bolts pictured? Im speaking about the large starter ground wire.

Im also having trouble identifying which wire is positive on the battery cables ? theres a solid black and a black with yellow stripe, I thought negative was with black with yellow but im second guessing myself for some reason...

should the starter ground wire take care of my issue with no power to the car then?

 

The NEGATIVE wire is the one with the Yellow stripe.
That goes to the LONG starter bolt(that would be the Top bolt).Put the neg wire circular connector on that bolt,then feed the bolt through From the Engine side through the rear iron, the trans and starter and put the nut on.(it may have been on the other way but Trust me it is easier to get the starter on and off when the bolt is this way.PLUS you do not loose the Neg wire when you have to remove the starter,it stays on that bolt!)

 

Thank you for the advice! once I switched that ground around and the other capacitor, I cranked it over and its getting fuel ... not sure on spark yet, I had a minor fuel leak to take care of.


I have another question now, Is the injector harness labeled with that colored stripe front or rear? Here's a pic of how its setup now, Im not sure if the primary/secondary injectors are labled front/rear somehow or if it matters which order they are hooked up in, although I would imagine so considering the front and rear rotors fire at different times!?

 

Front primary is Light Green, front secondary is LG/White, rear primary is LG/Black, rear secondary is LG/Red.

 

So based on what you said and my picture .. It looks like I have the front secondary injector plug mixed up with the rear secondary, but the only one that has a color stripe is that orange one.... any other way to tell for the primarys?

 

You can do a continuity test at the ECU. 3F=R. Secondary, 3C=R. primary, 3H=F. Secondary,3E=F. Primary. Not sure what you mean by "Orange one" though.

 

sorry it looks orange on the front secondary connector in my picture . I assume thats supposed to be "red" correct?

not sure what you mean 3F , 3C , 3H. AND 3E though? is that a measure of resistance or continuity?

 

They are the names of the pin locations at the ECU.

 

Ok thanks man Im going to see what I can do tonight!

 

Okay guys I got this thing running good however I'm having issues with 3800rpm-4000rpm backfiring and hesitation .

When I unplug the rear secondary and front secondary injector plugs the car hits a brick wall rev limit like at 4000rpm.

With both plugged in it will rev to 5k or so then starts popping real bad like unburnt fuel out the exahust. the rear rotor seems to make no difference whether its injector is plugged in or not but I know its working fine below 4k , this would mean the ECU is at least getting some fuel in through the front secondary correct? so I cannot figure out if it's an injector or electrical issue.


Here are pics of the connectors that need a home , if you can help me identify them I would really appreciate it!

First up is this yellow wire w/ white stripe. under the upper rear intake area -


Next is obviously a ground for something, but what? and is this the cause of my hesitation? I did an emssions delete so could this be extra? there are no matching connectors within its reach.

 

bump ! still looking for an answer guys!

 

The Y/W goes to the water temp gauge sending unit.
The second one is indeed a ground and (normally) goes to a copper tongue screwed to the firewall near the wiper motor.

 

Thank you for the reply! But where is the water temp gauge sending unit located.. lol? Im guessing your meaning the water temp sensor in the back of the water pump housing?

 

Nope. Try very near the Oil Pressure Sender.

 

Okay I see , I noticed I have an extra connector down there! it was just a little short to reach, I guess the harness needs moved around a little! gonna try it and Ill let you know what happens! I must be missing the copper tongue by the firewall because I dont seem to have one .. not sure why my secondarys are only working on one rotor either, the rear injector harness seems to be the culprit. I swapped injectors and its still not firing the rear rotor after 3800rpm

 

Figured it out! Turns out the JSPEC ECU was bad! I swapped my N332 in there an now it revs to 7k! thanks for the help everyone.