[xj40] Grounds-Earths: Locations, Identification & Service Photos

For the archives I have uploaded photos that document my
work to locate, identify and service every ground stud in
our '93, a process I completed during the past calendar year.

I’ve become convinced that clean grounds are critical to the
problem-free performance of the XJ40. I hope these photos
will serve as a sort of quick-reference to help owners
locate the specific ground point associated with a
misbehaving circuit.

Cheers,

Don

http://www.jag-lovers.org/snaps/snap_view.php3?id=1388098570
http://www.jag-lovers.org/snaps/snap_view.php3?id=1388091656
http://www.jag-lovers.org/snaps/snap_view.php3?id=1388071677
http://www.jag-lovers.org/snaps/snap_view.php3?id=1388068907
http://www.jag-lovers.org/snaps/snap_view.php3?id=1388009913--
Don B : '04 XJR '93 XJ40 VDP ex-'88 XJ40 Sovereign
Franklin, TN, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

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 !

Don

Excellent work!
During the 15 years that I have owned my '94 model XJ40 I have almost
religiously cleaned and dielectric greased every earth terminal that I have
come across around the car. (and the positive ones!- I also had problems
with the jump start post connections under the dash)
I have too often looked at beautiful Jaguars and seen,dry, rusty and
corroded terminals - under the bonnet and in the boot - they are asking for
trouble.
As part of my maintenance program I routinely spray WD40 onto every
termination that I have cleaned and treated in the past as well as all the
plugs and sockets around the car and hope that I am preventing future
problems.
Thanks again and I wish a good new year to everyone.

Norman Watkins
'94 my 4.0 XJ6S.
Scotland----- Original Message -----
From: “Don B” dnbyr@aol.com
To: xj40@jag-lovers.org
Sent: Sunday, December 29, 2013 4:08 AM
Subject: [xj40] Grounds-Earths: Locations, Identification & Service Photos

For the archives I have uploaded photos that document my
work to locate, identify and service every ground stud in
our '93, a process I completed during the past calendar year.

I’ve become convinced that clean grounds are critical to the
problem-free performance of the XJ40. I hope these photos
will serve as a sort of quick-reference to help owners
locate the specific ground point associated with a
misbehaving circuit.

Cheers,

Don

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 !

In reply to a message from Don B sent Sat 28 Dec 2013:

This is another superb and fantastically useful photo album, Don.

Many times I have seen answers posted on the forum including the
advice ‘‘have you checked the earth points?’’ This posting will be
very useful when that happens - whether the question is asked now,
or from an answer found from searching the archives.

My own car has been superbly reliable over the years, in no small
amount due to having always maintained the ground studs.

David–
The original message included these comments:

For the archives I have uploaded photos that document my
work to locate, identify and service every ground stud in
our '93, a process I completed during the past calendar year.
http://www.jag-lovers.org/snaps/snap_view.php3?id=1388098570
http://www.jag-lovers.org/snaps/snap_view.php3?id=1388091656
http://www.jag-lovers.org/snaps/snap_view.php3?id=1388071677
http://www.jag-lovers.org/snaps/snap_view.php3?id=1388068907
http://www.jag-lovers.org/snaps/snap_view.php3?id=1388009913


1992 Jaguar Sovereign 3.2 (1993 model) RHD 90.000 miles
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php

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 !

In reply to a message from dbcheshire sent Sat 4 Jan 2014:

Norman and David,

Thanks for the kind words as well as the affirmation that
keeping our electrical connections clean contributes to the
reliability of our cherished Jags. And thanks again to all
the pioneering members of this forum who have helped the
rest of us understand the importance of this type of
maintenance. I didn’t come up with this idea, I just
thought it would be helpful to have all the ground points
and battery power connections identified and photographed
for future reference.

Cheers,

Don–
The original message included these comments:

Many times I have seen answers posted on the forum including the
advice ‘‘have you checked the earth points?’’ This posting will be
very useful when that happens - whether the question is asked now,
or from an answer found from searching the archives.
My own car has been superbly reliable over the years, in no small
amount due to having always maintained the ground studs.


Don B : '04 XJR '93 XJ40 VDP ex-'88 XJ40 Sovereign
Franklin, TN, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php

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 !

I joined today and donated to help out the forum. I have a question, I need to see the ground points that are listed in your post but the pictures won’t open. Do i need a special viewer or chrome/internet explorer/edge/firefox to view?

Hi Gary,

Great to hear from you! Unfortunately, the Jag-Lovers forum transitioned to new servers several years ago and still have not gotten all of the large images transferred over, so all that are visible are the thumbnails.

You can find the ground points by referring to the Electrical Guide, which you can download at jagrepair.com. Note that most of the XJ40 guides are incorrectly filed in the XJ6 & XJ12 section.

Cheers,

Don

THANK YOU!!! My baby is dead in the water and can’t figure out why. It has NOTHING!!! wasn’t sure if there was a master fuse or relay

What is the year and model? What is the battery state of health and charge?

1994 XJ6 …battery was tested Good

Completely kaput ignition switch maybe?

What is the current state of charge of the battery? Jaguars require strong, healthy, fully-charged batteries.

What was the sequence of events. Did the loss of all electrical power occur suddenly, or has it been an intermittent problem? Did the vehicle sit unused for an extended period? We need more context, please.

Cheers,

Don

i had just driven it all day, went back out to go pick up dinner and it just turned over. i tried again the next morning and it turned over but then stopped and NOTHING. no dash/interior lights…horn…just like there is no battery in the car. battery was fully charged… tested and is good. was trying to find if there is a mega fuse…maybe 250amp somewhere in the positive cable but cannot find anything. 1994 xj6

Gary,

Seem to recall that on the ‘battery in the boot’ cars there could be a problem at the positive lead connection on the right side of the firewall corroding so nothing gets through to the engine / instruments.

1 Like

Hi Bryan! Sorry I haven’t been around lately. I’ve been at the Jaguar Forums since I bought an X350 several years ago. You remember correctly, as usual, that there is a jump start post on the firewall on the right side near the hydraulic brake boost pump/accumulator assembly.

Gary, before removing that jump post and cleaning the stud, wire terminals, washers and brass stud, disconnect the battery. If I recall correctly, the stud requires a deep 19mm socket (6 point preferred to prevent rounding the hex on the stud).

You can download the wiring schematics for your car at this link:

http://jagrepair.com/images/Electrical/Elect-Tech%20All2/93%20XJ6%20Electrical.pdf

A quick glance at Figure 6 suggests that failure of the Starter Relay could cause your symptoms, and another suspect could be the Central Microprocessor (CPU). A common issue with the CPU is water contamination of its electrical connectors or ingress into its case and circuit board due to clogged drains under the A/C evaporator, which allows water to pool in the tray below the evaporator and to slosh over onto the CPU while cornering. On LHD cars, the CPU is mounted on the firewall just to the right of the Climate Control Unit/Center Console. It takes quite a bit of disassembly to get to it, unfortunately.

A quick test would be to check the voltage between the firewall jump start post and a good ground, such as the ground stud on the right inner wheel well. You should measure a voltage just slightly lower than the voltage across the battery posts (which should be 12.6 volts in a fully-charged healthy battery).

Cheers,

Don

1 Like

One other thought is to check the fuses in the Center Console fuse box. I seem to recall that there is a fuse that can blow there and kill the instruments, cranking, etc. It may be a fuse for Accessories, but I can’t remember for certain.

1 Like

all the ones in the center console are 5 amp…i didn’t pull them to check will try that. I did have the battery out of the car and wire brushed/dielectric greased all grounds i could find…even the battery neg cable. the car turns over fine…all lights…horn…buzzers work…just no start. had to take a break due to the car sits so low…having to squat and stoop over to work on everything. i will get a voltmeter and check from the underhood jump post and a ground. Thank you for any and all advice

here is the beautiful offender

Hi Gary,

Your car is gorgeous! Thank you for posting that photo.

Based on your initial description of the problem, I understood you to be saying that the engine would not rotate when attempting to start, and that you had no lights on the instrument cluster. A cranks-but-won’t-start condition is very different from a no-crank condition.

The first two things I would recommend are:

  1. When you turn the key to position II (ON) but do not attempt to start the engine, do you hear the fuel pump run briefly to prime the fuel system? If not, suspect a problem with the pump or its circuit. Bryan N has posted a fantastic diagnostic procedure that has worked for me every time I have needed it.

  2. Measure the static voltage between the jump post and ground, then have a helper crank the engine and observe how low the voltage sags. If the voltage sags below about 10.4 volts while cranking, the ECM will not trigger the ignition to fire. Many voltmeters cannot respond quickly enough to read the true voltage sag, so consider any reading below 11 volts to be cause for concern.

A common cause of low voltage while cranking is corrosion on the many battery power and ground connections throughout the car: battery posts and cable terminals, negative cable connection to the body, the connections at all three fuse boxes, the firewall jump start post, the starter and alternator, and both ends of the engine ground strap.

Cheers,

Don

Crank no start? First thing to swap is the rotor. My 94 did the same thing last summer.

1 Like

Gary - you might find this thread helpful:

Be forewarned it is quite lengthy but it does contain a lot if information.

1 Like