[xj] XJ6 S3 Starts won't stay running

The car starts, runs for about 3-4 seconds then dies.
This is what I have done in the last couple of weeks, just
in case you all see something I may have done to cause this
prob.
Fixed the Electric Windows, Fixed the central locking ,
Removed the Oil Cooler pipe from above the Oil Filter and
replaced an 0 ring, Changed Oil and filter at same time. The
next day the Car would not start. It cranked but no go.
Short story, after reading Doug Dwyers Fuel Pump Circuit
diagnoses, I replaced the Fuel Relay on the firewall and the
Car started and ran, I did not drive it I just let it tick
over for a few minutes.I then proceeded to replace all the
Fan Belts. This took a few days as I was called out of town.
When I finally got the Belts back on I started the car , but
again I only let it tick over for a few minutes. I then
checked out the Electric Arial, that does not go up or down
and found the Power (Red) wire had been cut. When I rejoined
the Red wire the Arial Motor constantly ran. Pulled the
Arial apart and the Internal hoist Cable was twisted and
broken. So Disconnected the Wires going to the Arial, put
the Taillight back and thought will fix it later. Went to
start the car and that�s when the current problem arose.
So,what have I done to sort this? I put the wires back on
the Arial for a start, except the Red one :slight_smile:
I have been back through the testing Fuel Circuit procedure,
the only problem I see there is that the Red Diode Pack only
gives 2.5Volts at Terminal 5. I have not been able to get a
new Diode Pack from the local Parts shops (Saturday) so will
try the Auto electricians tomorrow, although is this part a
Jag specific Part?
I have searched the Archives and found some postings on the
same symptoms.It sounds like the Air Flow to the Intake is
not right.
I have checked both the Black Rubber Joiners going from the
AFM to the Intake but all are looking good. I pulled them
off and checked them then carefully re-installed them making
sure that the Clamps were tight and no possibility of air
leaks. I found the metal pipe going from the Air Pump to the
Cylinder Head was only just in the rubber tube, so pushed it
in and tightened it. Checked all Vac pipes running to and
from Intake Throttle area, tightened a couple.
After testing the Voltages at the AFM connector (all OK) I
found by removing the AFM connector that the car would run
if I held the throttle open � to � it ran for long enough to
warm the engine then I turned it off, although it ran very
lumpy.
When I reconnect the AFM connector, the car only runs for
3-4 seconds and dies, it sounds like a fuel starvation, if I
try to pump the throttle once its running it chokes and
backfires. If I hold the throttle partly open when starting
it revs at 2500 revs or more for a couple seconds then dies.
I will try to get the new Diode Pack tomorrow, but I don�t
know that�s the answer.Where is the ECU situated?(Sorry I
have not managed to get a workshop Manual yet.)Is the ECU
likely to be the cause?–
Oldmac2006
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Just for fun, I’d measure the fuel pressure to see if it’s 34-36 psi at the
fuel rail. You can use the hose to the cold-start injector and connect a
pressure guage to that. A regular water-pressure gauge from the hardware
store, along with fittings to adapt to a barbed hose spigot will work.–
Alex
79xj6L SII (BRG + wires)
86xj6 SIII (Black)
61 Sprite MkII (Red)
Menlo Park, Calif.

Oldmac2006 wrote:

The car starts, runs for about 3-4 seconds then dies.
This is what I have done in the last couple of weeks, just
in case you all see something I may have done to cause this
prob.

[clip]

After testing the Voltages at the AFM connector (all OK) I
found by removing the AFM connector that the car would run
if I held the throttle open � to � it ran for long enough to
warm the engine then I turned it off, although it ran very
lumpy.
When I reconnect the AFM connector, the car only runs for
3-4 seconds and dies, it sounds like a fuel starvation, if I
try to pump the throttle once its running it chokes and
backfires. If I hold the throttle partly open when starting
it revs at 2500 revs or more for a couple seconds then dies.
I will try to get the new Diode Pack tomorrow, but I don�t
know that�s the answer.Where is the ECU situated?(Sorry I
have not managed to get a workshop Manual yet.)Is the ECU
likely to be the cause?

===================================================
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In reply to a message from Oldmac2006 sent Sun 15 Jul 2007:

Had a very similar issue with a 85 XJ-6. Car would start flawless,
but than die within approx a minute. We were searching for two
weeks three floors down in the garage…
Either the cold start relay or the diode element on the bulkhead
(close to the battery on the LHD version) was damaged. I think it
was the diode element. When we opened the damm thing we found it
full of coolant (had a water hoose explode on the highway allmost a
year earlier).

Good Luck!–
Nikolaus
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In reply to a message from Oldmac2006 sent Sun 15 Jul 2007:

Thanks Nikolaus for the Reply.
Is the Diode Pack a Jag specific Part?
or should I be able to purchase it from any Auto Electrical
shop??
Where is the Cold Start Relay??

Cheers

Mark
Queensland
Australia
85 XJ6 Sovereign–
The original message included these comments:

try the Auto electricians tomorrow, although is this part a
Jag specific Part?
After testing the Voltages at the AFM connector (all OK) I
found by removing the AFM connector that the car would run
if I held the throttle open � to � it ran for long enough to
When I reconnect the AFM connector, the car only runs for
3-4 seconds and dies, it sounds like a fuel starvation, if I
know that�s the answer.Where is the ECU situated?(Sorry I
have not managed to get a workshop Manual yet.)Is the ECU
likely to be the cause?


Oldmac2006
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
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Is the Diode Pack a Jag specific Part?

Yes, and a bit pricey. If you’re handy with a soldering iron you can
replace the internal components for about $3.00

Where is the Cold Start Relay??

You don’t have one, although the (poorly edited) Jaguar manuals say that you
do, as they confuse the 6-cyl and V12 systems. Click here and scroll down a
bit to “identification of firewall relays” :

http://www.jag-lovers.org/xjlovers/xjfaq/toptwenty.htm

Cheers
Doug Dwyer
Longview Washington USA
1995 XJRFrom: “Oldmac2006” spare@intocomputers.com.au

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In reply to a message from Doug Dwyer sent Mon 16 Jul 2007:

Thanks Doug
I am capable of replacing the diodes and the resistor.
I have already had it apart but the colors on the resistor
are not clear enough to know what size it is.
The diodes look like IN4000 or IN4006 ?
Do you know the resistor size?
Also can you confirm the Diode Specs as IN4000?
Many Thanks
Cheers
Mark
Queensland
Australia
85 XJ6 4.2 Soveriegn–
The original message included these comments:

Yes, and a bit pricey. If you’re handy with a soldering iron you can
replace the internal components for about $3.00


Oldmac2006
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I had the same problem with resistor colors—couldn’t make them out. Alex
can suggest something suitable.

I think a '4006 diode would be fine but honestly can’t remember what was
originally used. Been a long time.

Doug Dwyer
Longview Washington USA
1995 XJRFrom: “Oldmac2006” spare@intocomputers.com.au

I am capable of replacing the diodes and the resistor.
I have already had it apart but the colors on the resistor
are not clear enough to know what size it is.
The diodes look like IN4000 or IN4006 ?
Do you know the resistor size?
Also can you confirm the Diode Specs as IN4000?

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In reply to a message from Oldmac2006 sent Sun 15 Jul 2007:

Thanks Doug,
I’ll ask Alex about the resistor.

Cheers
Mark
Queensland
Australia
85 XJ6 4.2 Sovereign–
The original message included these comments:

The car starts, runs for about 3-4 seconds then dies.
the only problem I see there is that the Red Diode Pack only
gives 2.5Volts at Terminal 5. I have not been able to get a
When I reconnect the AFM connector, the car only runs for
3-4 seconds and dies, it sounds like a fuel starvation, if I


Oldmac2006
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–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php

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As you can see, the diode number increases to indicate increased breakdown
(reverse) voltage. Any 1N400x will be fine in a car, as long as the 1 amp
current limit is ok.

The resistor can be measured by cutting one lead and using an Ohmmeter on the
resistor’s leads. Or, if you can see colors use them with…

http://www.weethet.nl/english/hardware_resistor_calculator.php

Metallic color bands indicate accuracy none = 20%, silver = 10%, gold = 5%.
More accurate small resistors will have it printed, like ±1%. Power
resistors usually have everything in print.–
Alex
79xj6L SII (BRG + wires)
86xj6 SIII (Black)
61 Sprite MkII (Red)
Menlo Park, Calif.

Doug Dwyer wrote:

I had the same problem with resistor colors—couldn’t make them out.
Alex can suggest something suitable.

I think a '4006 diode would be fine but honestly can’t remember what was
originally used. Been a long time.

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Oops, left out the diodes…

http://www.allelectronics.com/cgi-bin/category/205/Diodes.html

Cannara wrote:> As you can see, the diode number increases to indicate increased

breakdown (reverse) voltage. Any 1N400x will be fine in a car, as long
as the 1 amp current limit is ok.

The resistor can be measured by cutting one lead and using an Ohmmeter
on the resistor’s leads. Or, if you can see colors use them with…

http://www.weethet.nl/english/hardware_resistor_calculator.php

Metallic color bands indicate accuracy none = 20%, silver = 10%, gold =
5%. More accurate small resistors will have it printed, like ±1%.
Power resistors usually have everything in print.

Alex
79xj6L SII (BRG + wires)
86xj6 SIII (Black)
61 Sprite MkII (Red)
Menlo Park, Calif.

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In reply to a message from Cannara sent Mon 16 Jul 2007:

Thanks Alex, thats handy info for the resistors and diodes.
Unfortunately the colors on the resistor are very unclear.
When I put a tester over the resistor(I have removed it)I
get inconsistant readings of 2.5 to 19.7 using the 20M
setting on my Meter. I’m not familiar with this type of
testing, so not 100% sure if I have the settings right.
Anyway, I have ordered a second hand Pekron Diode Pack from
a wrecker, it will be here in a day or so. In the meantime I
will see if I can organise a pressure tester for the Fuel line.
Many thanks
Cheers
Mark
Queensland
Australia
85 XJ6 4.2 Sovereign–
The original message included these comments:

The resistor can be measured by cutting one lead and using an Ohmmeter
on the resistor’s leads. Or, if you can see colors use them with…


Oldmac2006
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Ok, if you’re up in the Megohm range then your fingers are effectively
shorting your readings if you’re holding the metal of the leads. If so, just
avoid touching the metal of the tester or resistor.–
Alex
79xj6L SII (BRG + wires)
86xj6 SIII (Black)
61 Sprite MkII (Red)
Menlo Park, Calif.

Oldmac2006 wrote:

In reply to a message from Cannara sent Mon 16 Jul 2007:

Thanks Alex, thats handy info for the resistors and diodes.
Unfortunately the colors on the resistor are very unclear.
When I put a tester over the resistor(I have removed it)I
get inconsistant readings of 2.5 to 19.7 using the 20M
setting on my Meter. I’m not familiar with this type of
testing, so not 100% sure if I have the settings right.
Anyway, I have ordered a second hand Pekron Diode Pack from
a wrecker, it will be here in a day or so. In the meantime I
will see if I can organise a pressure tester for the Fuel line.
Many thanks
Cheers
Mark
Queensland
Australia
85 XJ6 4.2 Sovereign

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In reply to a message from Cannara sent Tue 17 Jul 2007:

Problem solved!
Thanks for all the help. The second hand Pekron Diode pack
arrived, I plugged it in and she’s running fine now.
I took the Diode Pack apart first to check the colors on the
resistor.
Red, Violet,Gold,Red. these colors do not add up if you
check the resistors at the website. Gold should be the First
color.
http://www.weethet.nl/english/hardware_resistor_calculator.php
No worries, it works.I will ask at the Local Tandy’s if they
can match these colors, I would like to fix the old one for
a spare.
Driving it yesterday reminded me why I’m doing this :slight_smile: What
a great vehicle to Drive!!
Thanks again.
Cheers
Mark
Queensland
Australia
85 XJ6 4.2 Sovereign (That Goes :-))–
The original message included these comments:

Anyway, I have ordered a second hand Pekron Diode Pack from
a wrecker, it will be here in a day or so. In the meantime I


Oldmac2006
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Sounds good Mark. The colors don’t make sense, since there whould be 3 in a
row from one end that are not metallic. If you have you Ohmmeter, just put it
across the resistor one way, then the other, to see what you get. This will
show if the diode(s) are influencing your reading.–
Alex
79xj6L SII (BRG + wires)
86xj6 SIII (Black)
61 Sprite MkII (Red)
Menlo Park, Calif.

Oldmac2006 wrote:

In reply to a message from Cannara sent Tue 17 Jul 2007:

Problem solved!
Thanks for all the help. The second hand Pekron Diode pack
arrived, I plugged it in and she’s running fine now.
I took the Diode Pack apart first to check the colors on the
resistor.
Red, Violet,Gold,Red. these colors do not add up if you
check the resistors at the website. Gold should be the First
color.
http://www.weethet.nl/english/hardware_resistor_calculator.php
No worries, it works.I will ask at the Local Tandy’s if they
can match these colors, I would like to fix the old one for
a spare.
Driving it yesterday reminded me why I’m doing this :slight_smile: What
a great vehicle to Drive!!
Thanks again.
Cheers
Mark

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