[v12-engine] SEC: UNCLASSIFIED:-ECU Wiring Questions?

V12-Engine
1

---------------------- Forwarded by Johnathon Ronayne/ARMY/DOD/AU on
14/10/2003 07:27 ---------------------------

LT Johnathon Ronayne at ROBERTSON BARRACKS
13/10/2003 16:14

cc:

   Start

Well, After a bit of fiddling, I dicovered the WS lead from the Amp to the
ECU to have a break or ten.
I Now wish to replace it. The whole damn length of it to save going through
this crap ever again! Problem is, I’m not too sure what kind of wire I can
replace it with or whether it’s even worth doing. I guess this one’s for
you Kirby but has anyone else had this problem but with multiple breaks?
I’m worried that If I replace the accessable lenght in the engine bay the
wire may just break somewhere else. If it won’t, what should I replace the
bit I can get to with?
Funny thing was, I rejoined the wire at the first broken bit I found, but
when I put everything back together and moved the wire, the car wouldn’t
start again. Had to be that wire though, it’s the only thing I was playing
with at the time!
On a side note, does anyone know of anyone in Australia that fiddles with
our ECU’s (specifically my 16CU)???
I have a Catalyst version 16CU in my HE and I need to know how to make it a
non catalyst version, if that’s possible, without sending to Englandon
vacation to visit AJ6, but if all else fails… It’ll have to travel.

Thanks again for your help, I’d be lost without the list!

John R
1984 XJ-S HE, 1978 XJ-S, 1969 MG-B MkII
‘Who needs a Holden anyway?’

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Subject: SEC: UNCLASSIFIED:-v12-engine-digest V3 #723 '84 XJ-S HE No

2

Well, After a bit of fiddling, I dicovered the WS lead from the Amp to the
ECU to have a break or ten.
I Now wish to replace it. The whole damn length of it to save
going through
this crap ever again! Problem is, I’m not too sure what kind of wire I can
replace it with or whether it’s even worth doing.

Yes you can do it. First, see Sean’s instructions for wire splicing:

Then get some 18 gauge SLX or GLX wire (good to 125C) from some place like
Waytek.
Since this is going to be a continuing process you may want to bite the
bullet
and get a bunch of different colors:

http://order.waytekwire.com/CGI-BIN/LANSAWEB?WEBEVENT+L16194112305731E6131C8
0M+M36+ENG

Follow the wire to a place in the harness where it is in good shape, away
from the engine.
For example, I recently replaced all the ones for the sensors etc, splicing
in the
main bundle along the right fender near the starter relay. Do the splice,
then
use some high temperature “split loom” to recover the bundle.

Ed Sowell
76 XJ-S

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3

Checking my files I see that I got my wire from

https://www.delcity.net/tstore/servlet/pagebuilder?frame=Home

They will sell 100 feet, whereas Waytek won’t sell less than 250 ft.
I got 7 different colors of 18 gauge SLX for $31 plus shipping. They
do have a minimum order of $25 so I had to add another item of some kind.

I later discovered the SLX is a bit thick for fitting into some connectors.
GLX has a thinner insulation, with the same rating, but Del City doesn’t
seem to offer it.
Waytek does.

Ed Sowell
76 XJ-S

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4

Johnathon.Ronayne@defence.gov wrote:

'84 XJ-S HE No Start

Well, After a bit of fiddling, I dicovered the WS lead from the Amp to
the ECU to have a break or ten.

Well put! Obviously, the FIRST break brings the car to a halt, but
by the time I had the sheath stripped off I’d bet mine was broken in
about ten places. Once it’s brittle enough, it just crumbles.

I Now wish to replace it. The whole
damn length of it to save going through this crap ever again!

Actually, probably not necessary. It only seems to get brittle right
there over the engine. It joins up with a larger harness in the RR
area of the engine compartment, and by that point it was limber on my
car. So I just cut out the brittle stuff and spliced in new wire
from there.

Problem
is, I’m not too sure what kind of wire I can replace it with

Well, there’s a good question. When looking at coax wire, typically
there are impedance concerns – as in, if you use the wrong impedance
the signal might get attenuated and lost above some frequency or some
such. The highest frequency here is 6500 x 6 / 60, or 650 Hz.
That’s very low as such things go, which would lead me to conclude
that signal attenuation isn’t a concern here. Some of you electrical
weenies please confirm or contradict that, such things are not my
specialty.

I suspect the ENTIRE reason this thing is a shielded wire is to
prevent it picking up signals from other electrical pulses throughout
the car. That being the case, any coaxial wire would work. You
could buy some of that stuff used for audio/video patch cords in bulk
and use it. You might be able to find something high-temp, teflon or
whatever, which would be great.

I spliced in a short length of audio/video patch cord myself, and
even used a Motorola plug as a connector instead of the original
bullet connector. Works fine. I understand others have successfully
used non-coaxial wire for the short distance from limber coax to the
ign amp, which would seem to indicate that perhaps EF is not that big
a deal here. If true, that might make using regular teflon-coated
wire a good plan.

or
whether it’s even worth doing. I guess this one’s for you Kirby but
has anyone else had this problem but with multiple breaks?

Where all have you found multiple breaks? Are you just looking at
the first 18" of that wire, or are you checking other places, such as
in the trunk? The first 18" should be replaced, all the way back to
where the wire is no longer brittle, but I don’t recall any reports
of breaks elsewhere.

I have a Catalyst version 16CU in my HE and
I need to know how to make it a non catalyst version, if that’s
possible, without sending to Englandon vacation to visit AJ6, but if
all else fails… It’ll have to travel.

I’m not entirely sure you need to do anything. If I were you, I’d
install oxygen sensors (3-wire type) and use the ECU as is, unless
there’s something else you haven’t told us.

– Kirbert

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5

Well, After a bit of fiddling, I dicovered the WS lead from the Amp to the
ECU to have a break or ten.----------------------------------------------------------------------------------

My car is older and the ECU wire loom from under the RH wing, where it exits
the engine bay, right back to the boot, is in good condition.
All the wiring in the engine bay has been replaced.
On that note, as other listers said, you only need splice the cable to where
it exits.

You have heard already about how brittle the injector wiring will be ?
Where it lies in the valley is about the worst place on the car for any wiring.

In Darwin you might have to hunt around for good coax cable. Even shielded
cable should work, which is not quite the same as coax.
Stay away from hobby shops, they probably have junk. Try telecom or your
own army workshops. For a short term fix just about any wire will work if
you want to get
mobile in a hurry.

On a side note, does anyone know of anyone in Australia that fiddles with
our ECU’s (specifically my 16CU)???
I have a Catalyst version 16CU in my HE and I need to know how to make it a
non catalyst version, if that’s possible, without sending to Englandon
vacation to visit AJ6, but if all else fails… It’ll have to travel.

John R
1984 XJ-S HE, 1978 XJ-S, 1969 MG-B MkII

Prestige, or H&H in Melbourne have some electronic expert in tow who fixes and
modifies the things.
However, as Kirby said, does not seem an obvious reason why you need a
different version to what you have.

Richard Dowling, Melbourne, Australia, 1979 XJ-S & 1985 XJ6

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6

Richard Dowling wrote:

Even
shielded cable should work, which is not quite the same as coax.

Hey, don’t leave us hangin’! Please explain the difference!

Stay
away from hobby shops, they probably have junk. Try telecom or your
own army workshops. For a short term fix just about any wire will
work if you want to get mobile in a hurry.

I presume what you’re saying is that any coax or shielded wire will
work, but it might not work long in the environment, you need to find
something that will withstand the heat?

– Kirbert

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7

Well, as some of us “weenies” know, you can make just about anything work in
a pinch. I would recommend a FEP (Flourinated Ethylene-Propolylene) jacket
that is rated for heat ranges of 90C. There are other jackets that offer
better resistance to oil and gas, but whatever you have available is the
only thing that really counts. As far as the electrical concerns, the run
is too short and the frequency too low to be of major impedence issues. If
the run started to exceed 25’ then some capacitance from the cable and
terminations can lead to signal distortions, but usually at much, much
higher frequencies. The A/V patch cord and RCA plugs will work, but I
question how long, as the jacketing really isn’t made for extreme
environments and the tinned RCA plugs can develop residual corrosion in high
heat and humidity situations. Gold plated plugs can overcome that, but they
still aren’t optimal couplers. A good coaxial connector is the way to go if
you wish to keep all signal integrity at it’s optimum. A complete 360 degree
termination of the shield is what coax needs to properly ward off stray
signals. “Pigtailing” one end of the coax by twisting together the shield
can change the impedence properties, again, this probably doesn’t apply to
the signal levels that we are talking about here. In a pinch, I have used
twisted pair wires with shield and drain in place of coax on low frequency
lines. It yielded a slightly noisier signal, but it may work in this
application if the right jacketing can be found such as TPE (Thermoplastic
Elastomer).

Troy Elbert
74XJ12L-----Original Message-----
From: owner-v12-engine@jag-lovers.org
[mailto:owner-v12-engine@jag-lovers.org]On Behalf Of Kirbert
Sent: Tuesday, October 14, 2003 11:12 AM
To: v12-engine@jag-lovers.org
Subject: Re: [v12-engine] SEC: UNCLASSIFIED:-ECU Wiring Questions??

Richard Dowling wrote:

Even
shielded cable should work, which is not quite the same as coax.

Hey, don’t leave us hangin’! Please explain the difference!

Stay
away from hobby shops, they probably have junk. Try telecom or your
own army workshops. For a short term fix just about any wire will
work if you want to get mobile in a hurry.

I presume what you’re saying is that any coax or shielded wire will
work, but it might not work long in the environment, you need to find
something that will withstand the heat?

– Kirbert

Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting
services and resources including Photo Albums, Event Diary / Calendar, On
Line Books and more !

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8

I’ve got a couple of meters of MIL SPEC 1553 data bus wire I borrowed from
an avionics lab when I was taking a course at the Pax River Navy Test
school. I was always thinking of using it for this particular XJS
application, but I was never able to pull up the temp specs on the internet
after typing in the nomenclature marked on the side of the insulation.
Anyone out there know the specs for 1553 data bus wire and if it would
handle the heat under the hood?
Patrick
82 XJS HE

Richard Dowling wrote:

Even
shielded cable should work, which is not quite the same as coax.

Hey, don’t leave us hangin’! Please explain the difference!

Stay
away from hobby shops, they probably have junk. Try telecom or your
own army workshops. For a short term fix just about any wire will
work if you want to get mobile in a hurry.

I presume what you’re saying is that any coax or shielded wire will
work, but it might not work long in the environment, you need to find
something that will withstand the heat?

– Kirbert

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9

At 04:12 AM 15-10-03, you wrote:>Richard Dowling wrote:

Even
shielded cable should work, which is not quite the same as coax.

Hey, don’t leave us hangin’! Please explain the difference!

– Kirbert

Kirbert, I would not have you hanging.

This subject is more the province of high frequency electronics, and my work
is mostly at the other end of the spectrum around 50/60Hz and DC.

Coax cable is designed for high frequency signals, and has a characteristic
impedance which is low enough not to attenuate signals as they propagate
along its length. Think of TV signal connections which is a typical coax
application. To get it right the insulation material must have a specific
dielectric constant and thickness between the outer shield and inner conductor.
The outer shield is a capacitor for the inner conductor, which with the self
inductance of that conductor helps get the impedance correct.
That shield also acts as a shield against outside interference.

Shielded cable looks similar, but it is not specifically designed for high
frequency work. It is intended to screen the inner conductor from outside
interference. It will shield the signal from outside interference which has
frequencies of a few kHz and upwards. It is good protection against “noise”
radiated from an ignition system for instance, or a nearby radio transmitter.

It does not help protect against induced signals you can get if you are
close to powerful magnets, transformers and heavy current cables running at
50/60Hz.

People write whole books about this subject, but that is not for me.

Richard Dowling, Melbourne, Australia, 1979 XJ-S & 1985 XJ6

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10

Richard Dowling wrote:

Shielded cable looks similar, but it is not specifically designed for
high
frequency work. It is intended to screen the inner conductor from
outside
interference. It will shield the signal from outside interference
which has
frequencies of a few kHz and upwards. It is good protection against
“noise”
radiated from an ignition system for instance, or a nearby radio
transmitter.

Of course it is also used for the opposite reason. To shield radio
recievers (esp Loran) from noise caused by wiring in aircraft. Typical
noise producers are ignition wiring, alternator /generator, voltage
regulator, strobe lights, gear/flap motors etc
Steven Hall

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