[xj40] Fuel Fail Codes Come and Go

XJ40
1

My engine’s performance has varied over the past couple
weeks. Sometimes, it’s ran very smoothly without the
slightest skip. At one point it was skipping terribly and
running very rich accompanied by black soot on the tail
pipes. So far, I’ve only got Fuel Fail codes when the car
wasn’t running with the key turned so that the fuel pump
hums and all the warning lights come on. At first it was
Fuel Fail 17, referring to the throttle position sensor.
Later I got Fuel Fail 44, referring the oxygen sensor, I
believe. Then Fuel Fail 37, something to do with the EGR
system. And now, it’s running back to running good again
but skipping a bit when it’s first cranked and is back to
Fuel Fail 17. …?

I’ve been wanting to give my car a tune-up. I guess I’ll
start with the plugs and wires but all these codes coming up
have me confused as to what else I need to look into.–
Richard - 1992 Sovereign (4.0L)
Fountain Inn, South Carolina, United States
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2

In reply to a message from Enfield303 sent Thu 14 Jun 2007:

i think a full tune-up is a good idea which includes spark plugs,
plug wires, distributor cap, rotor button, fuel filter, air filter
and possibly a new coil and O2 sensor…if you have not done so
recently I would also do an oil & filter change as well as a tranny
fluid & filter change…this way you have covered the ‘basics’ and
can eliminate the possibility that one of these items is causing
your issues…this alone can sometimes ‘cure’ some weird and
erractic issues…you also need to insure your battery is properly
charged…a low battery can cause all sorts of false failure codes
to be thrown by the ECU…you can’t judge the state of the battery
charge by the fact that it can turn the engine over while
cranking…a low charged battery can still have enough juice to
spin an engine but not enough to properly energize the electricl
systems…i would also recommend cleaning the electrical
connections of all of the sensors that feed a signal to the
ECU…clean them with electronic contact cleaner and a small brush
and then apply dielectric grease to them…one more thing to do is
clean your throttle body thouroughly…i suggest you remove it
before cleaning it so that you can do a better job…check to be
sure nothing is obstructing the airflow into the MAFS such as
leaves or pieces of an old air filter…also check that all of the
bolts on the intake manifold are tight…they can work loose and
create a vacuum leak…speaking of vacuum leaks you should check
all vacuum hoses for possible leaks…if you have any doubts about
a hose I would just replace it since it is not very expensive…if
you still have issues after this you will have to go through the
process of elimination by checking and/or replacing items that can
throw a fuel fail signal…i am not sure exactly where Fountain
Inn, SC is but I live in Lancaster, SC…samll world sometimes…–
The original message included these comments:

My engine’s performance has varied over the past couple
weeks. Sometimes, it’s ran very smoothly without the
slightest skip. At one point it was skipping terribly and
running very rich accompanied by black soot on the tail
pipes. So far, I’ve only got Fuel Fail codes when the car
wasn’t running with the key turned so that the fuel pump
hums and all the warning lights come on. At first it was
Fuel Fail 17, referring to the throttle position sensor.
Later I got Fuel Fail 44, referring the oxygen sensor, I
believe. Then Fuel Fail 37, something to do with the EGR
system. And now, it’s running back to running good again

–
Cliff - '93 XJ40 Sovereign (4.0L)
Lancaster/South Carolina, United States
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3

In reply to a message from Cliff Archie sent Thu 14 Jun 2007:

Yeah, I’m not having much money these days but I will be
giving it a tune up as soon as I can. I might not be able
to replace a lot of parts at once, but I will get it done.
I’ve got the oil change and air filter taken care of
already. So next I’ll be getting the plugs and wires and
keep going from there. The weather’s been rainy lately and
before then, it was almost too hot outside for me to ever do
anything. The car’s actually been running better with the
rainy weather. I’ll be back out there checking on those
sensor connections, the intake, and the battery when I get a
chance. I’d also been thinking about replacing that O2
sensor ever sense I got that warning light but I haven’t
figured out where exactly it is as of yet…

Fountain Inn is a typical small southern town southeast of
Greenville, not quite 100 miles away from Lancaster. If you
had ever been here, I’m not surprised that you wouldn’t
remember it. There’s not really much to see…–
Richard - 1992 Sovereign (4.0L)
Fountain Inn, South Carolina, United States
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4

In reply to a message from Enfield303 sent Fri 15 Jun 2007:

Hi Richard,

A cheap fix I recomend (may be doesn t fix anything or may fix all,
but also evitates new electrical gremlins): spray some WD40 or
similar stuff in ALL electrical conectors at engine bay (well,
except the high voltage ones at coil and spark plugs), and even try
it at O2 sensor conector once you find it. This kind of products
remove water from them and are electrical conductors. Try it, it
doesn�t harms and may fix something.

Regards,

Daniel–
Daniel Blum, '92 XJR 4.0, manual gearbox, LHD, VIN 653523
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5

Daniel

Yes WD40 may well do some good but is a dielectric lubricating fluid, NOT a
conductor - just imagine the problems if you sprayed a conducting fluid into
a multipin connector.

NW

spray some WD40 or

similar stuff in ALL electrical conectors at engine bay (well,
except the high voltage ones at coil and spark plugs), and even try
it at O2 sensor conector once you find it. This kind of products
remove water from them and are electrical conductors. Try it, it
doesn�t harms and may fix something.

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 !From: “xjr fanatic” daniel_blum_v@hotmail.com
To: xj40@jag-lovers.org

6

First off: you only get failure codes when pressing the VCM button in
position II (engine starter not engaged or engine not running)
Secondly the 02 Sensor report is most likely a result of being fouled
from the main cause so not something to be concerned about.
The EGR would seem to be in the same ball park as the EGR though that
code usually relates to the solenoid valve (at the LH rear of the engine
from the driver seat) there is a blue bottomed solenoid vale with vacuum
hoses that run to the EGR and electrical connections. If the EGR
solenoid is hanging it could be the cause but its more likely the the
throttle put needs cleaning and or adjustment and perhaps cleaning of
the electrical connections with electronic contact cleaner and coating
with dielectric grease. If the vacuum hose was off you would not be
intermittent.

When was the last time you cleaned the idle orifice valve and the TPS or
the inlet air temp sensor and throttle body?
They all get gunked from the condensed oil fumes from the crankcase and
valve cover.

I’d hazard a guess your TPS is hanging up or malfunctioning some of the
time and causing the engine to go to limp home mode and/or your inlet
air sensor is gunked up. This problem generates the others. I’d start
there.

Its always a good idea to pull the plugs and give them a read for color,
soot, oil etc. on each cylinder to determine if you have an injector
sticking bad plug, bad valve etc. but my guess is you first need to fix
the TPS problem, make sure its clean and set properly.

Jay 90 VDP Majestic

Enfield303 wrote:

My engine’s performance has varied over the past couple
weeks. Sometimes, it’s ran very smoothly without the
slightest skip. At one point it was skipping terribly and
running very rich accompanied by black soot on the tail
pipes. So far, I’ve only got Fuel Fail codes when the car
wasn’t running with the key turned so that the fuel pump
hums and all the warning lights come on. At first it was
Fuel Fail 17, referring to the throttle position sensor.
Later I got Fuel Fail 44, referring the oxygen sensor, I
believe. Then Fuel Fail 37, something to do with the EGR
system. And now, it’s running back to running good again
but skipping a bit when it’s first cranked and is back to
Fuel Fail 17. …?

I’ve been wanting to give my car a tune-up. I guess I’ll
start with the plugs and wires but all these codes coming up
have me confused as to what else I need to look into.

Richard - 1992 Sovereign (4.0L)
Fountain Inn, South Carolina, United States
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7

In reply to a message from Jay sent Fri 15 Jun 2007:

I think you’re right, Jay. I was looking for that throttle
position sensor and I found a bundle of wires that connects
through one of those blue cylinder-shaped plastic
connectors. The wires were tagged ‘‘throttle pot’’ so I
followed that bundle of wires down and found that it leads
to something located on the bottom of my throttle assembly
right above my oil filter. That wiring and the object it’s
attached to are all covered in black gunk. I want to clean
all of this up in the way you describe but I haven’t found a
detailed explanation of how to do so. I just haven’t fooled
with it yet, afraid that I’d mess something up. I’ve been
meaning to order a Haynes repair manual on this car. I was
looking through the site’s XJ40 book but so far I haven’t
found much about this.–
Richard - 1992 Sovereign (4.0L)
Fountain Inn, South Carolina, United States
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8

In reply to a message from Enfield303 sent Thu 21 Jun 2007:

since the rest of the post string was lost during this post I hope
i do not repeat any advise you may have received already…to
clean the TPS I would suggest you unplug the electrical connector
and remove the throttle body and TPS as a single unit…this way
you will have much better access to both and can do a thourough
cleaning of both…one word of caution is to try and not get any
cleaning solvent inside of the TPS…i would suggest you use
electronics cleaning solvent since it will not damage electrical
components and dries quickly without leaving a film…you can avoid
this by turning it upside down where the shaft is pointing toward
the ground…that way when you clean the TPS body the solvent will
not run down the shaft and into the sensor itself…if you decide
to remove the TPS from the throttle body ‘BE SURE TO MARK ITS
POSITION IN RELATION TO THE THROTTLE BODY’…if you do not install
the TPS back in the EXACT same position it was removed the settings
for the transmission shift points could be altered and the ECU
could get a errant signal and cause the engine to run either rich
or lean…you can set the TPS position by using a voltometer and
back probing the wires but why go through this extra effort if not
needed…you can take this opportunity to also clean the throttle
body on both sides of the butterfly…make sure the butterfly is
not binding and opens and closes easily…as you reassmble
everything be sure to put some dielectric grease on the electrical
connector…–
Cliff - '93 XJ40 Sovereign (4.0L)
Lancaster/South Carolina, United States
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9

In reply to a message from Norman sent Fri 15 Jun 2007:

Are you saying that dielectric grease should not be used or WD40
should not be used on multi-pin connectors?–
The original message included these comments:

Yes WD40 may well do some good but is a dielectric lubricating fluid, NOT a
conductor - just imagine the problems if you sprayed a conducting fluid into
a multipin connector.

–
John 90 XJ40
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10

In reply to a message from John S sent Thu 21 Jun 2007:

WD40 should be used in multipin connectors. Norman was making a
correction to what I indicated in one of my ‘‘lapsus brutus’’. WD40
is in fact a dielectric and should be used in multipin connectors
(or any kind of connectors).

Regards,

Daniel–
The original message included these comments:

In reply to a message from Norman sent Fri 15 Jun 2007:
Are you saying that dielectric grease should not be used or WD40
should not be used on multi-pin connectors?

The original message included these comments:

Yes WD40 may well do some good but is a dielectric lubricating fluid, NOT a
conductor - just imagine the problems if you sprayed a conducting fluid into
a multipin connector.

–
Daniel Blum, '92 XJR 4.0, manual gearbox, LHD, VIN 653523
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
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11

In reply to a message from Enfield303 sent Thu 14 Jun 2007:

On a recent trip thru gatlinbirg my engine light came on code fail
fuel 17 also can you help with what you did to fix yours and what
to look at befor I take it to my mechanic.

Thanks David

Anderson,sc–
The original message included these comments:

Fuel Fail 17, referring to the throttle position sensor.

–
nsde
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12

In reply to a message from nsde sent Thu 30 Oct 2008:

I’ve had that before along with a code 14, coolant temp sensor. I
replaced the coolant temp sensor and have no problems…I got the
sensor from autozone was less than $30…there’s has a 2 year
warrenty while all the others I found was only 1 year–
jsm 94’ XJ40
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13

1990 Sovereign owner here:
I have recently had some success in chasing down the dreaded code 44. I should share some of the things I found…
I noticed a gurgling sound coming from around one of the injectors. New injector seals weren’t very expensive and they were shockingly easy to change. This cleared the code 44 - but then it came back. Ugh! Most of us can relate to this frustrating situation though. I carried on. Just yesterday, I found the real culprit and it was a bad ground connection on the intact manifold ground, just by the #1 injector. I’m sure it was intermittent and simply contacting on the day I changed the injector seals!
Anyway, there’s two things to look at if anyone else is grappling with code 44. Hope it helps.