E36 M42 cut wiring - help needed

[danielzzz]

Hello ! First time posting here,but not the first time I've gotten help.Resorted to this forum (via google) many times over the years and I want to say what a great community !
Anyway,here's the problem.I've got an unbelievably bad condition E36,which I bought last winter for snow driving.Anyways,started fixing stuff on the car,as snow's coming and found out the engine harness is half melted.I can't even believe this thing ran.Fixed every melt cable,except for 4 that were cut.Three of them are coming from the x6458 junction (the rectangular box in back center of engine bay).Ran these cables with a multimeter,two of them respond to ECU pins 6,24,28,34,55,54,52,51 which are pins for grounds and ignition coils.Cable colors green/white and blue/yellow.
The third one runs through the same pins plus pin 25,but the multimeter doesn't give a sound signal,just resistance (probably going through resistor).Color black/green
I'm uploading a photo of the cables/place just for reference.I think these cables are grounds,but where does it mount and is it combined in one ?
I know there are two grounds coming from the plastic box that has the cam,crank and knock sensor connectors mounted on it.In my case,box probably melt and they threw it away,so cables are free,but I've got one ground cable only(black with white).

Fourth cable that got me wondering is the one coming from the 7 pin ignition coil connector.It's brown,so I guess it's ground,but it doesn't seem to go to the x6458 box.Could this be actually mounted on the ground point at the back of the shock tower


Thanks in advance.

[bmwman91]

What year is your car?

[DesktopDave]

Sounds like you have your work cut out for you! Pun only half-intended.

The E36 did have a unitized plug for the coil pack. I don't have any pics (or much of anything else helpful) but I figured I'd comment to keep this thread up at the top.

I'm pretty sure you don't need the ETM (you seem very competent with a DMM), but here's a link to Miller Performance's BMW archive just in case.

I'm not sure this applies to your car specifically, but BMW's typical wiring colors are brown for chassis grounds. Various black wires with strips of many colors are used for control circuits and "floating" grounds.

[bmwman91]

To be honest, if the harness is really badly hacked up and full of crimps and solder joints...find an undamaged replacement and swap it in. They are generally a couple hundred dollars, and carry a lot less risk of failure than one with a bunch of repairs. There are a TON of harnesses on https://car-part.com/ (a nationwide dismantler database). It's under "Wiring Harness (Engine)" and if yours is a 1993-1995 model then I think that they are all the same part. Prices seem to range from $150 to a lot more, which is better than eBay and you can call the wrecker to ask questions.

Trying to track down an intermittent fault inside of a sheath (due to a bad solder joint, compromised insulation, etc) is a real hassle. In particular, a chopped up ignition section is one of the worst things to have. The switched primary leg is shielded, and the inner conductor sees upwards of 400V spikes every time a coil is fired, making for a high risk of arcing to the grounded outer shield, EMI, and a hazard.

[danielzzz]

Thanks for the replies,guys.I was pretty busy last month,so had almost no time for the car.
Today I opened the plastic box in the centre of the engine bay.Seems like the blue/yellow and black/green cables are coming from the engine harness plug(near the fusebox).Checked out a pinout of an X20 connector (I think it's the same for all E36s) and turns out one cable is for reverse lights,other is for starter relay unloader (which is actually strange,because the starter is working perfectly).
Only thing that's left to figure out is the green/white cable,which actually goes into a cable "unifier",into a thicker green/white cable,which goes towards the diagnostic and ignition coil connectors.

P.S.Do any of you guys using the monoblock ignition coil have a ground cable,that bolts to the strut tower ?
Also,tried finding another harness,but couldn't find one in good condition.I live in a small country,so have to order from internet etc,and I don't want to wait or spend money on this car.