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Old 01-07-2018, 07:06 PM   #1
durk80
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Default Best way for re-wiring fuel injectors?

I have a 91 240 of which I would like to replace the fuel injector orange and green/white wires far enough back where heat hasn't taken its toll. While the insulation is still good, the copper wire underneath is oxidized. I know that each of the 4 pigtails tie in to one larger wire, but the question is, what is the best way to join 4 wires to a single wire?

Thanks for any help or advice in advance!
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Old 01-07-2018, 07:52 PM   #2
dl242gt
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You could probably get a section or good used harness from one of the folks here like Dave Barton. Soldering the wires together and using a quality heat shrink is a good way to join them together.

There are also butt connectors with solder inside. You heat them with a heat gun and the solder inside joins the wiring. The outer cover acts as heat shrink and you get a sealed connection.
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Old 01-07-2018, 11:56 PM   #3
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Corroded wires are a problem. As an experiment, use a big soldering iron and try to tin the end of the wire. Hopefully, the heat and flux in the solder will burn off the corrosion and will wet/tin the wire properly. If this doesn't work, keep cutting back the wire until you find a good section. If you can't get solder to stick to a single wire properly, soldering a group together won't work and crimping will be unreliable.

Use a heat gun to soften up the black plastic harness sheathing so you can roll it back, or slit it carefully and rewrap with electrical tape.

For 4-to-1 you can use "copper crimp sleeves" (cheap at home depot electrical dept) but you'll need to figure out a good crimp tool for them. You could also use a crimp sleeve, with a cheapo tool, and solder it. Make sure to put the heatshrink on before crimping/soldering. When crimped/soldered, pull hard on the wires and they should hold. 10 or 20lbs force seems reasonable for 12gauge wire.

You can buy new injector connectors and/or pins, or pre-pigtailed, at rockauto/240turbo/diyautotune.
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Old 01-08-2018, 09:45 AM   #4
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I add extra flux when soldering and the solder always sticks. I use this flux and it works well. When I'm done soldering I remove the flux residue with rubbing alcohol. I use the Weller WLC100 soldering iron. Using an iron that is too hot can damage the insulation.
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Old 01-08-2018, 09:59 AM   #5
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TBH if the injector wires look bad, lots of other wires in the harness are most likely as bad or worse. Instead of chasing bad wiring every time something happens (and it will), replace the under-hood harness and get on with your life.
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Old 01-08-2018, 12:48 PM   #6
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It is not particularly difficult to clean up corroded copper wires. You need two solutions

In one plastic cup, fill up with 250 ml of normal white vinegar. Mix in normal white table salt. Start with 15 ml and continue adding until you achieve saturation (it no longer dissolves and just precipitates into the bottom of the cup). Warm vinegar will dissolve more salt.

In a second plastic cup, fill with 250 ml of water and add baking soda. Add 15 - 30 ml of baking soda and stir.

A third cup with clean water. Demin would be nice but not critical.

Dip stripped wires into the vinegar solution. Swish around for a couple of minutes until the copper is nice and clean.

Remove wire from vinegar solution. Shake off excess solution and dip into baking soda solution to neutralize the vinegar then rinse in clean water. Dry the wire with a hair dryer.

The wire should now be good for soldering or crimping. I prefer crimping because solder tends to migrate up the wire making is stiff and subject to failure (not to mention insulation damage); however, I have used both in a pinch. You can purchase multi point male spade connectors which can be used to bus together multiple female spade connectors which would allow for clean single wire crimp connections. If you use crimps, consider some conducting grease such as Oxgard under the crimp.

Or you could buy a new wire harness.
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Old 01-08-2018, 01:41 PM   #7
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If you decide to use spade lugs, then a good crimping tool will help a lot. I like the Paladin 1300 series frame with appropriate die set.

Last edited by Rusty_ratchet; 01-08-2018 at 02:26 PM..
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Old 01-08-2018, 10:15 PM   #8
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Firstly, thank you for all of the innovative (at least to me) ways of joining the wires.
I would love a brand new wiring harness! Yet for now, it looks like the more economical option looks like some open copper crimps are in order--after cutting back to better wire. If I remember correctly, the original wiring was crimped with a clear plastic heat shrink applied. (I believe that there was also some sort of glue further fastening the wires and keeping them from excessive vibration.) Not sure if it was soldered or not.

Love the vinegar/salt baking soda/ H2O and H2O bath method for cleaning the ends of the wire. That method sure cleans copper pots quite nicely!

I'll order some pigtails, tie in the wires using the copper crimps, heat shrink with sealant, and save up for a new wiring harness in the meantime.

Thanks again for all the helpful suggestions, the flux, the cleaning solutions, copper crimps--everything!
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Old 01-10-2018, 03:07 PM   #9
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Quote:
Originally Posted by Uncleknucklez View Post
TBH if the injector wires look bad, lots of other wires in the harness are most likely as bad or worse. Instead of chasing bad wiring every time something happens (and it will), replace the under-hood harness and get on with your life.
Agreed! Dave Barton is awesome, too!
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