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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
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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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Old 01-17-2018, 11:49 AM   #10
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Thank you for all of the helpful advice again! Before I go ripping out the injector wires, I was curious to what the voltage should be from pin to pin, as I do not have access to a noid light at the moment.

When I unplug an injector and probe both ends in the connector harness, should it be producing 12V at idle?
From my repair manual, the only spec it gave was for resistance. That, and to listen for the steady clicking on each injector.

The resistance for all 4 injectors were all in the normal range of 16 ohms.

I tried the test the other day and the voltage read around .3 for each injector connection at idle.

Thanks again for all of the help and pointers. Dave's wiring harness looks like an awesome summer job!
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Old 01-17-2018, 12:16 PM   #11
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Typically, the injectors are ground switched by the ECU to cause the injectors to operate. With the ignition switch in the run position; but, the engine not running, pull a plug out of one of the injectors and measure the voltage to ground on the two pins. For your high impedance injectors you should get 12 v on one pin and 0 volts on the other pin.

At idle, the injector operates with a relatively low pulse width. At 900 RPM it takes about 0.133 seconds to complete two engine crank revolutions (complete combustion cycle). On my B20E with sequential injection, at idle the injector is only open about 0.002 seconds during the two revolutions, so a duty cycle of about 1.5%. I assume you are trying to read the voltage across the injector terminals. Unless you have a scope or a very high end digital voltmeter with adjustable set up, you voltmeter is going to try and read the average voltage which, with a duty cycle of 1.5% would be 0.015 x 13.8 volts = .21 volts. My injectors are large resulting in relatively short pulse widths. If your injectors are OEM they are likely smaller resulting in a longer pulse width and a proportionally higher average voltage reading.
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Old 01-17-2018, 01:26 PM   #12
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Quote:
Originally Posted by 142 guy View Post
Typically, the injectors are ground switched by the ECU to cause the injectors to operate. With the ignition switch in the run position; but, the engine not running, pull a plug out of one of the injectors and measure the voltage to ground on the two pins. For your high impedance injectors you should get 12 v on one pin and 0 volts on the other pin.

At idle, the injector operates with a relatively low pulse width. At 900 RPM it takes about 0.133 seconds to complete two engine crank revolutions (complete combustion cycle). On my B20E with sequential injection, at idle the injector is only open about 0.002 seconds during the two revolutions, so a duty cycle of about 1.5%. I assume you are trying to read the voltage across the injector terminals. Unless you have a scope or a very high end digital voltmeter with adjustable set up, you voltmeter is going to try and read the average voltage which, with a duty cycle of 1.5% would be 0.015 x 13.8 volts = .21 volts. My injectors are large resulting in relatively short pulse widths. If your injectors are OEM they are likely smaller resulting in a longer pulse width and a proportionally higher average voltage reading.
Thanks 142 guy, for the wealth of knowledge! With the key on, I will probe for 12v on one terminal and 0 v on the other while having the black lead clipped to the intake manifold.

You have answered a question that has baffled me for a long time.
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Old 01-17-2018, 01:57 PM   #13
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A meter between the two pins, engine running, is not a good method.

You can use a noid light, or a test light between a positive source, like the positive wire, and the ground wire should blink. This will also confirm CURRENT! You can have 12v on a meter, but not enough current to operate and injector. Like if rez pack wires were also bad.


Waveform analysis thread. I have a couple fuel injector waveforms in there. You can see the injector opening in the waveform by the little opening hump. http://www.forums.turbobricks.com/sh...d.php?t=313652
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Old 01-17-2018, 06:53 PM   #14
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Quote:
Originally Posted by ZVOLV View Post
A meter between the two pins, engine running, is not a good method.

You can use a noid light, or a test light between a positive source, like the positive wire, and the ground wire should blink. This will also confirm CURRENT! You can have 12v on a meter, but not enough current to operate and injector. Like if rez pack wires were also bad.


Waveform analysis thread. I have a couple fuel injector waveforms in there. You can see the injector opening in the waveform by the little opening hump. http://www.forums.turbobricks.com/sh...d.php?t=313652
Good point. I will purchase a noid light!
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Old 01-17-2018, 09:22 PM   #15
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I finally bought a set for $15. I also use them to confirm power and current on components like washer motors, window motors, almost anything with a plug. It confirms the circuit is good before replacing a component.
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Old 01-17-2018, 09:34 PM   #16
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I finally bought a set for $15. I also use them to confirm power and current on components like washer motors, window motors, almost anything with a plug. It confirms the circuit is good before replacing a component.
You should also buy a current clamp
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Old 01-17-2018, 09:49 PM   #17
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Originally Posted by swedefiend View Post
You should also buy a current clamp
http://www.forums.turbobricks.com/sh...d.php?t=313652

Also just got a large jaw one with a custom BNC cable to go to the Picoscope. I can now do compression tests without pulling spark plugs.
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Old 01-17-2018, 10:01 PM   #18
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http://www.forums.turbobricks.com/sh...d.php?t=313652

Also just got a large jaw one with a custom BNC cable to go to the Picoscope. I can now do compression tests without pulling spark plugs.
Well, there you go.

I work with my box right in front of me. It's not a big deal. I know a lot of people like to park their boxes in a corner and work out of a cart. I dunno, not really a big deal for me to bust out my meter.

Also... I wouldn't worry too much about the concern in the other thread about the piercing leads.

I was taught primarily by a former Porsche technician that opened a race car building shop in Birmingham and a Volvo Master Technician. Both of them used piercing leads similar to mine (and I assume yours - SnapOn amiright?). I used them on customer cars at the places I worked and on my own... Including my megasquirted '83.

I've never worked on a space shuttle though, so... YMMV
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Old 01-19-2018, 05:19 PM   #19
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Well, there you go.

I work with my box right in front of me. It's not a big deal. I know a lot of people like to park their boxes in a corner and work out of a cart. I dunno, not really a big deal for me to bust out my meter.

Also... I wouldn't worry too much about the concern in the other thread about the piercing leads.
I have $3,000 of well organized Snap On tools an arm's reach away from me at all times in my service cart. I have to be efficient as a flat rate tech.

Included are my needle probes. I have been trained to never front probe terminals. We have the proper corresponding male terminals if I ever need to front probe or do a terminal drag test.
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