Recovering from Engine Fire - Wiring Harness Guidance

[Andy A]

Dad and son have have an 87 E30 that had a small engine fire. Principle damage is the wiring to the injectors. We have a donor car (85 E30). Is it possible to replace only the damaged part of the harness or will we need to replace it as a total unit? I'm reluctant to start removing the shrink wrap from the harnesses looking for a connector. We have the Bentley manual and we recently moved the manual transmission from the donor car to the 87. We did this with Jack stands, no lifts and no prior experience. I just want to calibrate you on our level of commitment not our skill set. A step by step procedure would be much appreciated.

[Kennethdriley]

I just had to change mine out so I do know about this. I have an 88 that has a screw together plug that rotted and caused my car to be towed 7 times home. you can replace just the wiring going to the injectors and temp sensors if you are good with a soldering iron and heat shrink tubing. the harness wires run through and down through the center of the manifold. You would need to cut off the old harness about 5 inches from the split off of the main harness. you will have about 6-8 wires that you must splice to the proper color coded wires on the replacement top harness. You can go to the junk yard and pull any harness from 85-88. 88 is easiest because as I said it has a screw together plug connecting the two. The wiring consists of a thick injector common wire, a thick 1-3-5 common wire, a thick 2-4-6 common wire, two thin wires that go to the temperature sender for the gauge, and either a single or double wire depending on model that goes to the other temperature sender for the motronic computer. I would NOT just twist the wires together and tape them as they will rot under the hood and cause erratic operation. You can slip heat shrink tubes over the wires, twist them together taking care to have the correct color codes, and solder them together and then slip over the heat shrink. I used a giant one inch heat shrink tube over my entire repair but you could use electrical tape to bind the finished wires. If you have any more questions just drop me a note,

[Andy A]

Ken:
Thanks for the note. We did a full swap taking the harness out of the 85 "donor" car. That harness is slightly different from the 87. The screw together plug and the position of the two sensors that connect to the transmission. I modified the harness (cut off the square connector and replaced it with the screw version). A little forsight would have made the process easier, I did the splice work bent over the car it would have been more comfortable on the bench. The transmission sensors were more of an issue. I had to pull the ones off the donor car. They are considerably longer and allowed us to make the connection to the harness up top. The initial configuration had those mate down by the starter. The 85 harness won't reach down there. While this configuration is less tidy, it is very effective. Next steps are to track down a draw somewhere in the electrical system that was present with the old harness. I'm hoping the new harness fixed it but I'm not usually so lucky. Then we want to get the donor car towed away in exchange for a new hood, sunroof handle and front ground effect (the black thing that attaches to the front bumper that covers the fog lamps). Jr is responsible for calling the local junk yards and making a deal. It's a shame you're so far away. We could meet for a cold one and compare stories.

[Kennethdriley]

Glad it worked out for you! Just be sure and keep an eye on those screw plugs because they rot the wires on the wire end and can cause no end of troubles. Mine would make connection for weeks at a time and then it would die like you turned off the key. I rode in so many tow trucks I felt like a hooker. I pulled the rubbers back on all the rest of mine and sprayed them with WD40 just to be sure. Wish you were Closer too!