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Wire loom repair

88trailcrawler

NAXJA Forum User
Location
OC SoCal
So, I was digging around in the engine bay A LOT the last few weeks dealing with the smog issue.

My wiring harness is down to individual insulated wires, mostly at the front of the valve cover, the plastic looms crumble to dust when you look at them and the tape that was inside has been reduced to fiber dust.

Everything works good and I want to clean up and wrap up.

I purchased some heat shrink tape and braided split loom from the electroncis store.

I was thinking removing all old plastic loom and tape, cleaning off wires, wrapping with heat shrink tape then covering with braided loom.

Not sure if the heat shrink tape is a good idea long term, thought I would post up for some comments before I get going.
 
The split loom from your local auto parts store will last like 6 months before its discolors, cracks and/or melts. I would actually like to find something a bit more durable than the OEM version if possible.
 
Look up Flexo F6.

Not sure that is the brand I got, but looks just like it.

I am thinking heat shrink tape wrap every few inches around the wires then at the ends and joints of the loom wrap?
 
The split loom from your local auto parts store will last like 6 months before its discolors, cracks and/or melts. I would actually like to find something a bit more durable than the OEM version if possible.
The loom I've been getting from JC Whitney has been holding up quite well (five years). At least in the black.
 
Do not use any tape's with an adheisive backing... It WILL get nasty....

The factory used duct tape, but that doesnt mean it's ok for us to do so, we plan on being in that engine compartment later on...
 
I ended up using hockey tape about every 6" -8" just to hold wires together.

Then used a braided split loom similar to the flexo with a bunch of mini zip ties.

I used the shrink tape just where wires exit the loom, didn't even shrink it down (no heat gun or torch)

I only did the Fuel Injection run from C101 down to O2 sensor.

It is much better now and suprisingly with all the moving around, everything seems to work fine.

Couple of questions:
- I found duct tape in the original harness - Comment above stated that was from the factory?

- I found 2 wires clipped off in the loom with the what appeared to be the factory cloth tape around the ends just under the MAP sensor - ??

- What is so special about that one wire that has the copper tape around it? - there was an extra bare wire inside the tape, but it didn't connect to anything at the sensor -??
 
The duct tape is factory, go figure...
The copper tape thing, is insulation for the over and under section of the wire harness, ie the stuff that goes past the exhaust. O2, Knock, and CTS.
 
Were the wires with the bare wire inside twisted?

Not sure I understand what you mean by twisted.

The pair of wires from C101 all the way down to the knock sensor are wrapped in a copper colored foil wrap. Inside that wrap was a third silver colored bare wire. This third wire was outside the sensor connector and it didn't look like it ever was inside the connector. The sensor connector only has two wire tabs (I think)

I don't know what this third wire is and if I should crawl back under there and try to connect it.
 
What I suggest, and do when building a harness up -
- first, go over the harness with a fine tooth comb and check for corroded connections, split insulation, weak splices, etc. Fix anything you find using quality sealant-lined heatshrink butt splice terminals and a ratchet or hydraulic crimper. Check to make sure it still runs well, then heat all the shrink tubing.
- next, moving from the ends of the harness toward the center, use cheap zip-ties to neatly bundle everything as cleanly as you can. Pay attention to where the harness will need to flex or have extra length to handle movement, i.e. where the harness crosses from the body to the drivetrain.
- next, lengthen or shorten any wires you've found to have a lot of slack or not enough slack to bundle neatly while zip-tying.
- substitute appropriate size fuses for any fusible links or at the very least, crimp in quality quick-disconnects or bullet connectors (of the same sealant lined heatshrink variety) so that replacing a fusible link in the future will not involve hacking up and soldering the harness.
- use dry vinyl harness wrapping tape to wrap all harnesses, again, working from the ends inward so that the tape does not unravel. A drop of super glue between the first and second wraps at the end of a harness branch can help as well. Do not fully wrap the harness where it needs to flex for installation or during operation, as the harness will be very stiff if fully wrapped. As you wrap with dry vinyl tape, clip the zip ties off just ahead of the tape, as they won't be needed anymore and will only make the harness lumpy.
- install split loom, again working from the ends of the harness inward. Wrap each junction or end with quality electrical tape such as 3M 1701, paying attention to the angles so that the tape will be evenly stretched and won't be able to bunch up by sliding sideways and leaving a trail of adhesive residue behind it. The last wrap or so should be unstretched so it doesn't peel off or "flag".

If you build a harness like this you should have no issues with it and it will be easy to work on if you need to add something in the future.

Oh, and the following products should never be used in wiring harnesses:
- scotchloks - need I say more
- duct tape (:nono: AMC and chrysler)
- wire nuts - those are for home electrical, not automotive.
- scotch tape, friction tape, harbor freight electrical tape - unless you want to end up wearing half the adhesive next time you work on the harness
- harbor freight zip ties - brittle plastic, fail very quickly in an automotive environment if they don't break while you're putting them on. Good for harness lash-up while prepping to vinyl wrap but that's about it.

I've seen some very clean harnesses built with waxed lacing twine, and done a bit of cable lacing on telco/datacenter racked equipment, but I prefer dry vinyl tape for automotive environments. It's a matter of personal preference, use whatever you like more.

The last full custom harness I built (94 XJ 4.0L/AX15/NP231 with full XJ EFI going into an e-carb equipped 87 YJ 258/A999/NP207 with a CJ7 dash swapped in) started up on the first crank after replacing one fuse and hasn't had a single problem yet. Since the factory disaster lasted 20 years, I expect the new harness to last at least that long. I'll have to take some pics and do a write-up on harness cleanup at some point, now that I think about it.
 
You might want to also look into PVC tape to wrap your finished wires with. I found this stuff a few years ago and have been using it ever since. It only sticks to itself and has to be cut off; it can't be unwrapped. No heat involved, no sticky crap on your hands, just use short sections at a time and stretch it, overlapping it as you go.
 
the whole thing? interior harnesses are annoying as hell but I can have the whole engine+engine compartment harness out of a jeep in around 20 minutes easy.
 
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