[xj-s] Marelli question

XJ-S
41

In reply to a message from mike90 sent Fri 30 Aug 2013:

Mike,

You made a statement that brings me in line with your logic. I can
recall that many have said that the V12 will not start or run if
the front crank sensor is faulty or disconnected. I don’t recall
that anyone had definitively said the same about the rear flywheel
sensor, until you clarified the point by stating that your engine
flat out quit when warm, and the gap at the rear sensor became too
great - resulting in the loss of the rear sensor signal to the
ECU. That settled it - the fault is probably not with the rear
sensor signal since there are some sparks. With regard to the
other musing about why Jaguar set the trigger fingers at 8 deg.
past TDC, it could be to eliminate the initial starting knock that
sometimes occurs in engines with some amount of advance timing at
start, and the slow revolution of the engine cranked by the
starter. But, nearly any engine will run with a surprising amount
of retarded (ATDC) timing if the spark is there. I (and I’m sure
some others) have inadvertently installed a distributor or two
retarded by a tooth or two, and the engine ran, but was a real dog -
and why won’t this engine run if there is no problem with the
sparks on A bank - maybe the drag of the dead B bank and not enough
throttle opening? Oh well, press on with the current plan of
attack.–
lockheed 92 XJS Cpe/97 LT1 Miami FL/ 96 XJS Cv 4.0 Austin TX
Austin, TX, United States
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42

In reply to a message from mike90 sent Fri 30 Aug 2013:

‘‘the front sensor gives TDC for the A bank’’

Nope, didn’t say that - the front sensor gives 8 deg ATDC.

''This means that they think that firing on A comes

directly from the trigger points on the crank sensor.’’

Not exactly what I said. I meant to say that A bank might run only
(retarded) on the trigger finger signals if the speed sense is
missing. But the fact that Mikes car quit completely with no speed
sense from the rear sensor trashes that thought.

‘‘You can’t fire the A bank cylinders ATDC!’’

Sure you can, and it would probably run if the sparks were there -
but like a dog. And if the sparks are there, why doesn’t it -
maybe that goes to the fueling issue. My guess for the 8 deg
retard would be that Jaguar wanted to avoid the start up knock.–
lockheed 92 XJS Cpe/97 LT1 Miami FL/ 96 XJS Cv 4.0 Austin TX
Austin, TX, United States
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43

In reply to a message from lockheed sent Fri 30 Aug 2013:

I am looking forward to getting the ECU back, and starting
again. Nothing like a great adventure in chasing a ghost,
lol. It may not mean anything, but given the fact that the
harness, the coils, the amps, the ECU, the CPU, the air temp
switch, the coolant temp switch, the rotor, the distributor
cap, plug wires,and who knows what else have been changed,
the only thing that has made COMPLETE logical sense, and I
kick myself for not checking it first, would be the engine
ground. That too, though, seems a bit out of question, as it
seems the A bank would stop firing as well. I bought this
car from a shop that seized it due to a non-paying customer.
I got this email, after I had paid for the car, and simply
asked what had been done. Here is the mechanics reply:

''As to my best of memory

Car came missing was arcing from coil to harness had new
harness made up in cailfornia new coils new modules,new
control units.after all that still ran same way,I think car
jumped time’’

This shop gave up. I don’t think it was diagnosed, they just
started changing parts. I don’t know what all the PO, and
the shop have done, but I have my work cut out for me. The
harness did appear very new. However, if the shop had it
made, then they are the ones that spliced into the control
wire that goes to the CPU. (Next problem to be solved)–
Gene Holtzclaw
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44

In reply to a message from Gene Holtzclaw sent Fri 30 Aug 2013:

So I wonder why some people are so quick to deny a potential
cause of a persistent problem. Obviously the problem was
there before all of the other work was done. The flywheel
sensor could be sending a signal that is not quite correct
but sufficient to confuse the ECU. It would take less than
10 minutes to eliminate that as the cause by cleaning or
replacement with the one that Mike is sending. I’m not
saying this is the cure, rather do not dismiss it until you
have eliminated it yourself. The electronics on these cars
play funny games with us. I know that I made a mistake early
on with my crankshaft position sensor when I used WD-40 to
clean the contact of the plug. This started strange
happenings that were driving me nuts until one of the kind
members of this forum reminded me that WD-40 is a water
displacement product made from fish oil and will leave a
film on electrical contacts. I then went out and got
electical contact cleaner and sprayed the connectors again
with great success. It sounds to me like the garage had no
clue and instead of diagnosing the problem they simply
started replacing parts and wiring. Most of which will prove
to have been a waste of energy. The original problem is
still there and has not been addressed.–
The original message included these comments:

I am looking forward to getting the ECU back, and starting
again. Nothing like a great adventure in chasing a ghost,
lol. It may not mean anything, but given the fact that the
harness, the coils, the amps, the ECU, the CPU, the air temp
switch, the coolant temp switch, the rotor, the distributor
cap, plug wires,and who knows what else have been changed,
the only thing that has made COMPLETE logical sense, and I
kick myself for not checking it first, would be the engine
ground. That too, though, seems a bit out of question, as it
seems the A bank would stop firing as well. I bought this
car from a shop that seized it due to a non-paying customer.

–
Jeff Schultz -1992 XJS 5.3L V12 -1995 X300 4.0L
Rutland VT, United States
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45

The reason: when you fit an manual box to a Marelli engine, and you
fit a new flywheel, you better be sure that the tooth count is the
same…

Do the Marelli and the pre-Marelli have differing numbers of teeth on
the ring gear? I could see that happening, as the Marelli might
require a number of teeth that are evenly divisible by 3 or 6 or 12,
whereas the earlier cars might have had some random number of teeth.
Still, the later geared starter is supposedly retrofittable to ANY
V12, so either the number of teeth didn’t change or the number of
teeth don’t matter enough to worry about it.

– Kirbert

// please trim quoted text to context onlyOn 30 Aug 2013 at 13:53, mike90 wrote:

46

In reply to a message from Kirbert sent Fri 30 Aug 2013:

Kirbert,

''From this fact alone, we can conclude that this trigger is not
used to fire 1A – even good electronics cannot predict the future.

Rather, this trigger would be used to fire the NEXT pair of
cylinders on the A bank – as well as the FIRST pair on the B bank -

  • after some computed time delay, or perhaps after some computed
    number of teeth on the ring gear pass the flywheel sensor. The 1A
    cylinder firing will be keyed off of the THIRD trigger, the one
    that happens about 112 degrees BTDC.’’

Interesting thoughts, but I don’t think that one can make such
conclusions. For example, if we set baseline timing on a mechanical
distributor at ‘‘0’’ deg. or even some negative amount, we are still
able to make it fire at some advance up to ~ 30-35 deg BTDC thru
the use of centrifugal advance weights and vacuum advance to
conform to some timing map - is that predicting the future? And we
can do the same using electronics - both methods basing their
actions on initial timing reference, engine speed, manifold vacuum
and a timing map. This is no more predicting the future than the
mechanical distributor. Granted, it may not be there when the
engine first fires at a slow cranking speed (just as it is not with
the mechanical method and you get that first firing knock), but as
soon as the engine begins to accelerate and produces a useable
speed signal (tooth counts or whatever) mechanically or
electronically and some manifold vacuum, the required spark timing
will be input and will be there.

‘‘Rather, this trigger would be used to fire the NEXT pair of
cylinders on the A bank – as well as the FIRST pair on the B bank–
-.’’

Need some clarification of what you meant by that. Each timing
finger produces a firing signal for one cylinder on the A bank from
which a firing signal for 1 cylinder on the B bank is computed. No
two cylinders on either bank fire simultaneously. Nor do one
cylinder on A bank and one cylinder on B bank fire simultaneously.
This can be confirmed by looking at the Marelli cap and rotor. Two
revolutions of the crankshaft give six firing signals (three timing
fingers twice around) to fire the six A bank cylinders sequentially
in firing order, and six computed firing signals for the six B bank
cylinders sequentially in firing order. The firing signals
alternate sequentially from bank to bank, with the B bank firing
signals in between the A bank firing signals - like when you put
your two hands together with your fingers interlocked (at a 60
deg ‘‘V’’ angle for sure).

Maybe only AJ6 Engineering can confirm or deny your thoughts in the
first quoted paragraph.–
lockheed 92 XJS Cpe/97 LT1 Miami FL/ 96 XJS Cv 4.0 Austin TX
Austin, TX, United States
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47

In reply to a message from JagsinVT sent Fri 30 Aug 2013:

Check T-Boy’s latest posting on the thread:

‘‘6.0L V12 idle woes – finally, some progress, sort of…’’–
lockheed 92 XJS Cpe/97 LT1 Miami FL/ 96 XJS Cv 4.0 Austin TX
Austin, TX, United States
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48

Interesting thoughts, but I don’t think that one can make such
conclusions. For example, if we set baseline timing on a mechanical
distributor at ‘‘0’’ deg. or even some negative amount, we are still
able to make it fire at some advance up to ~ 30-35 deg BTDC thru the
use of centrifugal advance weights and vacuum advance to conform to
some timing map - is that predicting the future?

No, it’s advancing the timing. If we were to move the pickups on the
electronic systems, that would be analogous. But we don’t move the
timing marks; rather, we use time delays. And there’s no such thing
as a negative time delay. Not unless your car is going reeeaally
fast, anyway!

And we can do the
same using electronics - both methods basing their actions on initial
timing reference, engine speed, manifold vacuum and a timing map. This
is no more predicting the future than the mechanical distributor.

True, but that’s because the timing is NOT based on a trigger that
hasn’t occurred yet! Rather, it’s based on triggers that have passed
in the past, and timing is chosen accordingly.

Granted, it may not be there when the engine first fires at a slow
cranking speed (just as it is not with the mechanical method and you
get that first firing knock), but as soon as the engine begins to
accelerate and produces a useable speed signal (tooth counts or
whatever) mechanically or electronically and some manifold vacuum, the
required spark timing will be input and will be there.

Based upon triggers that HAVE OCCURRED.

Need some clarification of what you meant by that. Each timing
finger produces a firing signal for one cylinder on the A bank from
which a firing signal for 1 cylinder on the B bank is computed.

No timing finger can be used to fire a cylinder BEFORE the finger
triggers a signal. So, a finger that passes ATDC on 1A cannot be
used to fire 1A – unless a delay of just a bit less than 360 degrees
is used, but that’d be stupid when you have two other fingers. It
CAN (and probably IS) used to fire the NEXT fire on the A bank and
the next available fire on the B bank as well. It just so happens
the next available fire on the B bank will come BEFORE the next fire
on the A bank, so I’d expect that each of the three fingers trigger
first a fire on the B bank and then a fire on the A bank, each
delayed a calculated amount based on the flywheel pickup and an
advance map. But that means that the 1A cylinder is not fired by the
finger that is positioned at 8 degrees ATDC but rather by the finger
that comes 120 degrees before that.

No
two cylinders on either bank fire simultaneously.

Well, not on THIS engine; it uses a distributor instead. But as far
as crank position is concerned, 1A and 6A fire at exactly the same
crank position, so as far as the Marelli ECU is concerned they are
both triggered by the same finger and using the same delay factor.
Only the distributor determines that one spark goes to 1A and the
next goes to 6A. In a “wasted spark” distributorless ignition –
which the Jaguar V12 had in its last year – both 1A and 6A are
sparked by the same coil and at the same time, and the spark that
happens on the top of the exhaust stroke is just wasted, it does
nothing.

– Kirbert

// please trim quoted text to context onlyOn 31 Aug 2013 at 6:51, lockheed wrote:

49

In reply to a message from Kirbert sent Sat 31 Aug 2013:

Guys:

First, let me get this off my mind:

This has been a tremendous thread- there is so little known about
the Marelli setup beyond the fire problems, and some of the best
and brightest (my opinion) on this list have been posting,
contributing in a very constructive way to Gene’s resolution. This
is what I truly love about this site, and it is not the first time
I’ve seen this kind of thread evolve. Really, really cool stuff,
and big thing is this: people are civil in their discourse but are
after the real deal in terms of how things work, and they press
their view but yield graciously when more information and thinking
come to light. That’s a tremendously important characteristic of
this list. I certainly know I don’t hold all the answers, and I
have really appreciated the spirited discussion by others who
really know their stuff to sort the details down.

Now, on to the matter at hand:

I did not know about the fouling problem of the sensors, especially
as regards poor triggering behavior: the crank sensor sits almost
perfectly below the front crank seal, and the flywheel certainly
has access to oil dribbles from the B bank cam plug and oil banjo
bolt, and can certainly see oil slung from a leaky rear seal. I
know my sensor is always wet with oil and always has been.

But I did not think about the false triggering consequences of
this. That is really significant for owners of this system, and a
simple maintenance of pulling the sensors and cleaning them off is
not hard to do. Triggering on electronic systems is always a
trouble point, and I appreciate the posts on this thread and on
others that have brought this to our attention.

However, this issue is not what is causing Gene’s problem, almost
for sure. We will get to the bottom of it, surely, when Gene gets
back early next week, and can devote some time to the pursuit.

My sincere thanks to the many who’ve offered their best thinking on
this along the way- we would not be where we are without you.

-M–
Mike, 1990 5.3 XJS Conv., 5-speed, SE-ECU, TT Extractors
Lakewood, OH, United States
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50

In reply to a message from mike90 sent Sat 31 Aug 2013:

Mike:
Nicely said, I feel the same way about the 40+ posts under
this topic so far. I will ad – many thanks to you for taking
the initiative and helping out with the harness and ECU. I
was almost 100% sure the ECU won’t be at fault. Why the engine
cannot fire on A-bank only is still puzzling – there is spark
from the coil after all, and if there is fuel, the engine
should at least try to start.

Having read about the history of that car, I foresee many more
emails before this is resolved.

Best regards,
Steve–
The original message included these comments:

not hard to do. Triggering on electronic systems is always a
trouble point, and I appreciate the posts on this thread and on
others that have brought this to our attention.
However, this issue is not what is causing Gene’s problem, almost
for sure. We will get to the bottom of it, surely, when Gene gets
back early next week, and can devote some time to the pursuit.
My sincere thanks to the many who’ve offered their best thinking on
this along the way- we would not be where we are without you.

–
'95 XJS V12 6.0L, saphire/tan
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51

In reply to a message from Kirbert sent Fri 30 Aug 2013:

Kirby:
Not sure this answers your question, but the 6.0L flywheel has
160 teeth and according to the JDHT ROM, the flywheel (engine
speed sensor) ‘generates 6 pulses per engine revolution’.
Steve–
The original message included these comments:

Do the Marelli and the pre-Marelli have differing numbers of teeth on
the ring gear? I could see that happening, as the Marelli might
require a number of teeth that are evenly divisible by 3 or 6 or 12,
whereas the earlier cars might have had some random number of teeth.
Still, the later geared starter is supposedly retrofittable to ANY
V12, so either the number of teeth didn’t change or the number of
teeth don’t matter enough to worry about it.

–
'95 XJS V12 6.0L, saphire/tan
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52

In reply to a message from mike90 sent Sat 31 Aug 2013:

Mike and others:
I had an off-line email exchange with Mr. Bywater regarding my
woes (covered under a different topic). He gave me some good
clues, which pointed my attention to section 18.3 of the JDHT-
ROM.

Again, this is for the 6.0L with Marrelli and may not apply
directly to the 5.3L.

p.4 ‘Engine cranking and starting’
‘Engine cranking and starting is recognised by decoding the
speed signal. The ignition timing during cranking and start
up is dependent on engine speed, intake air-temp and throttle
position.
The ignition timing moves from the crank to the run function
at 350 rpm.’

On p.12, the software functions of the 36CU are described and
it specifically mentions ‘crank-to-run threshold’ for
enrichment.

The above brings the following questions:

  1. Does Gene have juicy battery to crank the engine well-
    enough?
  2. Have the air-temp and TPS been checked/verified?

I still think if the harness to the A-bank is fine, there
should be a sign of life from the engine.

Steve–
The original message included these comments:

not hard to do. Triggering on electronic systems is always a
trouble point, and I appreciate the posts on this thread and on
others that have brought this to our attention.

–
'95 XJS V12 6.0L, saphire/tan
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53

In reply to a message from sbobev sent Sun 1 Sep 2013:

Steve:

OK, that is even more interesting information on how the Marelli
works…we should be collecting all of this somewhere, because
these details appear no where else to my knowledge. I will look at
my JHDT ROM and see if I can find anything in sec. 18.3. I fear my
edition may be too early, but I will check.

I don’t know about the sensors, but my plan for Gene is to have him
stub out the sensor inputs with resistors of appropriate values, if
needed, so that we have known, stable sensor inputs.

I agree, A looks good, and part of the reason he is not actually
running is because the fuel ECU lay unmounted with the vacuum line
detached (e.g., very rich fueling then, during cranking and
imminent running, as no vacuum = WOT to the ECU).

There’s more than a few things that have to be sorted here, and I
don’t know what the original symptoms of the engine control were
before all of this nonsense began. For example, the stuff Gene
posted here about what provenence he does know, I did not know
until I read it here.

This is why I have been pushing to drill down to the bottom on all
details, and confirm actual situations at each step, on the way
back up. This is the only way to ensure you know just what you
have.

On the ECU being bad: I agree, I didn’t think this should be bad
either, but without actually checking it, how should one think
about diagnosis? The ECU, if it is flaking out, can do so many
things, throw so many ghosts, that if you don’t take it out of the
picture at some point, and confirm you have some other problem, you
begin to spin about, without decent confidence of direction.

-M–
Mike, 1990 5.3 XJS Conv., 5-speed, SE-ECU, TT Extractors
Lakewood, OH, United States
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54

In reply to a message from sbobev sent Sun 1 Sep 2013:

This has nothing to do with fixing the problem, but gives a little
insight into the 8 degrees ATDC trigger points on the damper. This
is common with the 2 stroke engines I have worked on. For
starting, the spark coincides with the actual placement of the
trigger, or 8 degrees ATDC, to make cranking easy. Once the engine
is running, the electronics calculate advance and move the spark to
BTDC. It has to have an input showing engine speed before the
advance can be claulated…when you first turn the key there is no
speed, so no advance.

This means that the Marelli cars have to start using 8 degree ATDC
spark, and then calculate an advance once the engine picks up some
RPM.

Gene, have you tried using ether for a start yet?–
John. '95 XJS 6.0L convertible. Southlake, TX
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55

In reply to a message from Kirbert sent Sat 31 Aug 2013:

From Steve’s Post on 9/1:

p.4 ‘Engine cranking and starting’

'Engine cranking and starting is recognised by decoding the

speed signal. The ignition timing during cranking and start

up is dependent on engine speed, intake air-temp and throttle

position.

The ignition timing moves from the crank to the run function

at 350 rpm.’

On p.12, the software functions of the 36CU are described and

it specifically mentions ‘crank-to-run threshold’ for

enrichment.

Now, I think we can begin to get closer to what is happening.

‘‘But we don’t move the timing marks; rather, we use time delays.
And there’s no such thing as a negative time delay.’’

Not what I said, and I said nothing about positive or negative time
delays. And, ‘‘negative timing’’ as you call it, can be done
electronically - and it may or may not be incorporated in the
timing map.

I said:

‘‘Granted, it (proper spark timing) may not be there when the engine
first fires at a slow cranking speed (just as it is not with the
mechanical method and you get that first firing knock), but as soon
as the engine begins to accelerate and produces a useable speed
signal (tooth counts or whatever) mechanically or electronically
and some manifold vacuum, the required spark timing will be input
and will be there.’’

Steve’s info. from above:

''The ignition timing moves from the crank to the run function

at 350 rpm.‘’

So, that probably means it moves from the 8 deg ATDC to the timing
map. But, the map is still referenced to the timing fingers to
keep the timing map synched with respect to the crank. The rotor
determines where the properly timed spark will go in sequence.

The bottom line is that we are all just speculating at this point
about exactly how the Marelli really functions. And because I am
sure we would all really like to know for sure (and to settle the
mumblings), I will initiate an e-mail to Magneti-Marelli to see if
they will give up the secrets of their older system as it relates
to the Jaguar V12 from late '89 thru late '96.–
lockheed 92 XJS Cpe/97 LT1 Miami FL/ 96 XJS Cv 4.0 Austin TX
Austin, TX, United States
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56

In reply to a message from Gene Holtzclaw sent Thu 29 Aug 2013:

I was messing with the car today and had a chance to measure
the voltages on my 6.0L.

Ignition on. +12V measured on the WP wire for both coils.
No other live wires, including the tach wire on the A-ban
coil.

Steve–
The original message included these comments:

Now the next favor, just for knowing. Can anybody check, and
see if there is ANY voltage on the 3 wire connection on the
A coil, other than the 12 volts? Again, when I turn the
switch on, I have 12 volts as I should on one wire, but 3.4
volts on the opposite wire- the tach signal wire. If I am
reading the schematics correctly, this simply shouldn’t be
(I don’t think). I am not much up on circuitry of ECUs, and
even though its on the A side, isn’t there still a chance of
some sort of weird backfeed, that somehow ‘‘may’’ be effecting
the proper operation of this car?

–
'95 XJS V12 6.0L, saphire/tan
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57

In reply to a message from lockheed sent Sun 1 Sep 2013:

Hi Alan:
Glad to hear I am not the only one who feels this way.
Today a learned:

  1. The 6.0L beast can be started and will run with the MAP
    sensor off-line (the plastic tube from the A-bank to the
    Marelli ECU disconnected). Go figure.
  2. The Marelli jumper has no (obvious) effect on start/idle,
    the car runs the same w/ or w/o it.
  3. Despite the disappearance of the 45 second timer starting
    with VIN 188104 and all discussion we had here, Mr. R.
    Bywater in a private correspondence with me confirmed that
    the EFU ECU (the 36CU version) DOES have a timer – feedback
    is inhibited for one minute from start-up. It does not take
    CTS or O2 voltage to switch open to closed loop.
    This naturally begs the question – does the Marelli ECU
    also behave differently during this period?

Kudos to Alan (aka lockheed) for taking the initiative to
write to Marelli and look for more definitive answers.

Steve–
The original message included these comments:

The bottom line is that we are all just speculating at this point
about exactly how the Marelli really functions. And because I am
sure we would all really like to know for sure (and to settle the
mumblings), I will initiate an e-mail to Magneti-Marelli to see if
they will give up the secrets of their older system as it relates
to the Jaguar V12 from late '89 thru late '96.

–
'95 XJS V12 6.0L, saphire/tan
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58

In reply to a message from mike90 sent Sun 1 Sep 2013:

Mike:
My car starts and runs with the vacuum tube to the EFI ECU
disconnected. I actually drove it this way back and forth
to work…
I also found out that disconnecting the vacuum tube to the
Marelli ECU also does NOT prevent the engine from running.

Anyhow, after the ECU and the good CPS reach Gene, I would
recommend trying to start the car on the A-bank alone and
confirm it runs. We can then eliminate 50+% of the ignition
components.

If it doesn’t on its own or with ether, then, the problem
may prove to be much more difficult.

Cheers,
Steve–
The original message included these comments:

I agree, A looks good, and part of the reason he is not actually
running is because the fuel ECU lay unmounted with the vacuum line
detached (e.g., very rich fueling then, during cranking and
imminent running, as no vacuum = WOT to the ECU).
There’s more than a few things that have to be sorted here, and I
don’t know what the original symptoms of the engine control were
before all of this nonsense began. For example, the stuff Gene
posted here about what provenence he does know, I did not know
until I read it here.

–
'95 XJS V12 6.0L, saphire/tan
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –

// please trim quoted text to context only

59

Crazy suggestion. Can the engine be started with just the B bank and
will it keep idling? And then trouble shot from there. If one just
disconnects the +12V from the A Bank coil.On Sep 1, 2013, at 4:34 PM, sbobev wrote:

In reply to a message from mike90 sent Sun 1 Sep 2013:

Anyhow, after the ECU and the good CPS reach Gene, I would
recommend trying to start the car on the A-bank alone and confirm
it runs. We can then eliminate 50+% of the ignition components.

If it doesn’t on its own or with ether, then, the problem may prove
to be much more difficult.

Cheers,
Steve

'95 XJS V12 6.0L, saphire/tan

Ptipon
Sonnora/CA, 90 XJS-V12 conv, United States

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60

Paul,

 I wouldn't recommend doing this unless you also disabled all of the A

bank fuel injectors. Otherwise you will be dumping unburned fuel into the
cylinders, catalytic converters and mufflers on the right side.

 I have seen on the E-Type list where the Series III E-Types with the

5.3L V12 have been run using just one bank to evaluate possibilities of
better fuel economy at highway speeds. However, those V12s are equipped
with carburetors and it’s a little easier to cut off the fuel to one bank.

Regards,

Paul M. Novak

1990 Series III V12 Vanden Plas
1990 XJ-S Classic Collection convertible
1987 XJ6 Vanden Plas
1984 XJ6 Vanden Plas
1969 E-Type FHC
1957 MK VIII Saloon
Ramona, CA
P.M.Novak7@gmail.com-----Original Message-----
From: owner-xj-s@jag-lovers.org [mailto:owner-xj-s@jag-lovers.org] On Behalf
Of Paul Tipon
Sent: Sunday, September 01, 2013 6:50 PM
Cc: xj-s@jag-lovers.org
Subject: Re: [xj-s] Marelli question

Crazy suggestion. Can the engine be started with just the B bank and will
it keep idling? And then trouble shot from there. If one just disconnects
the +12V from the A Bank coil.

On Sep 1, 2013, at 4:34 PM, sbobev wrote:

In reply to a message from mike90 sent Sun 1 Sep 2013:

Anyhow, after the ECU and the good CPS reach Gene, I would recommend
trying to start the car on the A-bank alone and confirm it runs. We
can then eliminate 50+% of the ignition components.

If it doesn’t on its own or with ether, then, the problem may prove to
be much more difficult.

Cheers,
Steve

'95 XJS V12 6.0L, saphire/tan

Ptipon
Sonnora/CA, 90 XJS-V12 conv, United States

// please trim quoted text to context only