in a Book
Sump, Pump, Lines
FUEL LINES: The fuel pump in the XJ-S (in the
trunk) can put out nearly 200 psi. This is way too
much for ordinary fuel hose -- do not use it anywhere in
this fuel system. Most auto parts stores now carry "EFI
hose." It is much more expensive, but a fuel fire is no
Also, small high-pressure lines usually require special
clamps; basic worm screw clamps don't always seal small
hoses at these pressures. Some auto parts stores now sell
"EFI hose clamps" in various sizes (these type clamps will
only fit the size hose intended, you cannot just keep
screwing them down smaller liken a worm screw clamp).
Sometimes the special clamps are offered in a package with
the hose; make sure you have suitable clamps on hand or can
buy them separately before buying EFI hose without
the clamps. Greg Price says, "The Series III XJ6 has some
nice fuel injection hose clamps, and my local Jag tech
recommends Mercedes fuel injection hose clamps."
Stefan Schulz says, "Here in the UK, Farnell offer
stainless steel hi-torque hose clamps which are The Biz.
Highly recommended. Farnell Industrial are on telephone
[+44] 113-2636311." Schulz adds that he does
not recommend the fuel injection clamps from a
The high-pressure hose often is available only in short
pieces. It may be necessary to replace a long piece of hose
with a length of metal tubing (available at parts shops as
hydraulic lines -- cut off the fittings) bent to shape with
short pieces of fuel injection hose used at the connections.
Get a tubing bender; you don't want crimps at the turns.
Many of the lines (fuel, power steering, etc.) in the Jag
consist of metal tubing with threaded connectors and a short
length of hose in the middle somewhere, all sold under one
part number. The hose typically has a fake braided pattern
in the surface, and is no better than other British
non-metallic parts. The section of hose can easily be
replaced with the fuel injection hose with suitable clamps.
It is suggested that before you cut the original hose off,
you place measured marks on the tubes on either side of the
hose so that when you reassemble, the same overall length
can be established. You should also put alignment marks, so
the new assembly won't be twisted. Finally, if the hose is
within sight of the exhaust system or other hot parts, it
might be better to wrap it with some aluminum foil to
prevent the radiant heat from cooking the new hose.
The threaded fittings on the ends of some of these lines
have brass compression seals. The good news is that these
are the very same seals that are commonly used on household
plumbing, so they are available at any hardware store. The
bad news is that the tubes are so soft that the compression
of the seals sometimes has necked the tube, and you can't
get the old seal off nondestructively. Often, reinstalling
the tubes with the old seals will result in a leaktight
connection. If this doesn't work, buy new tubing and use new
seals and the old threaded nuts. You may have trouble
finding new nuts of the same thread.
The connections on the fuel rail and injectors themselves
on the XJ-S do not use clamps; the tightness of the hose on
the fitting is relied upon to prevent disconnection or
leaks. While this appears to work well, it makes some of us
nervous, especially if we have had one of these connections
apart for some reason. If you would like to secure the
connection, the best way is to use some steel wire -- see
ENGINE FIRES: The early
XJ-S H.E. had a reputation for engine fires. There has been
a redesign of the fuel rail on the engine to solve this
problem; the newer design is indicated by rectangular tubing
rather than round. All XJ-S H.E.'s were recalled and the new
system fitted -- if you still have the old, see your nearest
Jag dealer. The non-H.E., on the other hand, still uses a
fuel rail with round tubing.
Leaking fuel in an engine compartment is remarkably
difficult to ignite. Usually there have been obvious odors
and visible leakage for some time. Please do not ignore fuel
odors; the XJ-S shouldn't have any.
MORE ENGINE FIRES: The later XJ-S also has a
reputation for engine fires, also from the fuel lines!
Peyton Gill reports on "an XJ-S that had a little
pyrotechnics under bonnet. I asked the guy about it and he
said that the fire was put out within 30 sec (owner had a
fire extinguisher) and the estimate to repair was $2000.00.
There was not that much damage. The cause of the fire was
the ignition coil wire was about 1/4 inch from one of the
fuel injection lines (between rail and injector). The
ignition wire had been arcing to the line and eventually
worked its way through. I guess the physical damage and
ozone created by the arc eventually broke down the
Julian Mullaney adds, "There was a recall for cracked
injector hoses and injector bodies. Ozone from the
distributor leads causes the perished plastic. The recall
replaces the lead with a shorter one, and replaces the
injector. They looked up my car (vin no.) in their database
and the fix had already been done a long time ago, however
the problem persisted.
"The problem was ozone deteriorating the injector hose on
the right bank second cyl. from the firewall. It produces a
cracked surface of the rubber hose. You should look
carefully for this, it's not easy to spot.
"The dealer said that they were instructed to look for
visual damage to the hose and replace injector if needed.
"If" is the key word here. However, if it looked good, they
could get away with only changing the HT lead to a shorter
one (thus not close to the injector) and leave the original
injector hose. This leaves the chance that damage could be
have occurred to the hose but it's not visible yet, leading
to the following chain of events:
- upon initial recall they only replace the HT
- then the hose continues to deteriorate from initial
- then you see the damage to the hose a year or two
- pyrophobia sets in;
- then you call the dealer;
- then they tell you sorry, the fix has already been
- then you find that the recall was done sloppily;
- then you get pissed off;
- a) then you think about fixing the problem
- b) you call the dealer again and insist they fix it
- then dealer calls Jaguar to authorize 2nd repair
- they say OK
- you get it fixed for free
"Option b) worked fine with me, my local dealer was very
good about it."
Ron White adds, "I checked the recall database and the
recall only affects 1989-91 XJ-S models; this is a result
of: "The high tension lead from the ignition coil can move
from the production location closer to the #4A fuel injector
hose." <snip> "Vehicle description: coupes and
convertibles with Marelli ignition systems.""
White had a fire in his car, and thanks to having a fire
extinguisher in the trunk and knowing how to use it, his car
survived with almost no damage. "I have seen engine fires in
other cars and have seen people make the mistake of flinging
their hoods (these were American cars) open, only to have
the fire flare up 5 or 6 feet because of the added oxygen. I
opened the bonnet just enough to get the nozzle of the
extinguisher in, and gave it a good squirt. I then
cautiously opened the bonnet up and seeing no flames opened
it up all of the way and gave it a real good squirt!"
White's extinguisher happened to be a Halon type which works
wonderfully and leaves no crud on the engine but is bad for
the ozone layer and is in the process of being outlawed.
Experts seem to feel that a common powder type fire
extinguisher would probably work just as well, the only
disadvantage being that you'd have to blow all the powder
out of the engine compartment afterward.
One more note: White's car is an '86, meaning it's late
enough to have had all the updates to correct the early fuel
rail problems and too early to be covered by the recall for
the later cars with the Marelli ignition. "It appears that
the cause was a cracked body on an injector, and it was
squirting fuel directly on the distributor!" That fire
extinguisher is sounding like a better idea all the time,
CATALYTIC CONVERTOR FIRES (MARELLI IGNITION):
Might as well call it an engine fire; the level of damage is
comparable. Discussed at length in the section on the
STILL MORE ENGINE FIRES: Just when you
think you have the situation under control, the government
throws another monkey wrench in -- this time in the form of
oxygenated fuels, now required in California and many
metropolitan areas. Stephen Wood says, "We starting in
Spring 1996 having a substance called MTBE -- methyl
tutol-buytol,ethonanal, something like that -- blended with
our gas to help reduce emissions. Hopefully they will be
taking it out soon, as there has been a major hubbub about
it here. You see, it also melts things, like fuel lines,
carburetor gaskets, (especially the old rubber/cork type),
fuel tanks, braising material solder, etc.
"Last summer car fires were up significantly all over the
state, including my brother's '69 Camaro (it was restored).
MTBE melted through the carb gaskets on his vintage Holley
"At that point it got serious, and I checked my fuel
lines, and sure enough, they were going way squishy from the
inside out. In other cars we have seen it also has melted
"If you ask the insurance companies they have had a
slight increase but nothing to worry about. No problem,
right? Wrong! Most of the cars affected are cars that
the insurance industry won't provide fire, theft and
vandalism coverage on anyway. If you ask the CHP and the
firemen, they know that last summer was a major
So, you need a new type of fuel hose, right? "The problem
with the hose issue is that the rubber manufacturers are not
going to gear up for a California-only issue. However, some
of the new cars have fuel lines made out of a tygon
derivative, a newer plastic that is more resistant to these
blended fuels (New LT1- LT4- and LS1 GM motors). I don't
think there is a crossover app. as of yet, tygon is a bitch
to work with and has the characteristics of polypropylene
tubing, i.e., firm and not clampable. You have to use
special fittings with it.
"There is supposed to be some new silicone-based flexible
"rubber like" fuel line coming out soon from Gates or
Goodyear but I haven't seen it. So for now, I have been
keeping an eye on the situation and checking all pressurized
fuel lines every month, and replacing them every 6 months (I
have done this three times now). Vent lines are ok from when
I replaced them 6 months ago. I have been changing fuel
filters every 45-60 days (preventative mania), making sure
to cut open the old filter to see if anything weird develops
like little bits of rubber hose.
"I will have to take my gas tank out this summer, and
have it boiled and welded or just put in a new one. The
corrosion around the outlet is growing and I think it is
melting through the solder. I may just J&B weld it or
FIRE EXTINGUISHERS: After reading the previous few
pages, you have probably come down with a healthy dose of
paranoia regarding fires in the XJ-S. A fire extinguisher is
cheap, and may come in handy.
John Napoli suggests a built-in system like those found
on race cars: "It should be a lot easier to extinguish a
fire within the closed confines of the engine compartment
with the bonnet closed, and you could certainly react a lot
quicker than, say, opening the bonnet, saying "Oh, sh$t",
running for the boot, trying to find the fire extinguisher
that is underneath all your luggage, meanwhile the bonnet is
open and the flames are getting higher..." Of course,
keeping the extinguisher on the floor in front of the front
seat may help.
Emile A. DesRoches says, "If anybody is really interested
in a real "racing car" fire control system (sanctioning
bodies require a system plumbed in to spray at the engine,
fuel cell and driver's lap area), they can be obtained from
such organizations as Racer's Wholesale in Atlanta. From
experience as an SCCA tech inspector, I can say that they
may make a mess, but they work and clean up is inevitably
less expensive than replacing a fried V12 motor."
FUEL RAIL HOSE REPLACEMENT: This job is a cinch --
and it's highly recommended for anyone who notices aging or
leaking hoses. Take the entire set of injectors off the car,
which entails depressurizing the system, removing 24 nuts
and disconnecting a couple of fittings. Buy some 1/4" "fuel
injection" hose at any auto parts store -- if it's
reasonably priced it's the wrong hose, EFI hose is quite
expensive. The original hose may look like it has a cloth
surface and the aftermarket looks like rubber, but don't
worry about that -- the aftermarket is probably better. And
you might wanna get some steel wire, about 20 gauge.
One by one, note the position of an injector (the
direction the connector faces) and the length of the piece
of hose. Cut the old hose loose (don't lose the dished
washers), and reassemble by simply pushing the fittings into
a new piece of hose cut to the same length.
Now, if you're like me, you don't trust those push-on
connections. So, add considerably to your workload by tying
each hose connection with the wire. Wrap two or three times
around the hose, pull tight, twist, cut off, and fold the
twisted part over so it doesn't stab you whenever you're
fiddling around in the area. If you're concerned about
appearance here, stainless steel wire will look better.
You can buy stainless steel leader wire in any store that
sells fishing tackle, but it probably won't work well for
this task; the alloy used for leaders is very hard and
difficult to wrap. In a completely overblown sidetrack, some
advice on finding suitable stainless steel wire: Gregory
Price says, "I got a spool of SS wire in the Help section at
Gordon Clefton suggests, "We use stainless steel safety
wire in four sizes in aircraft applications: .020"; .025";
.032"; and .041". The wire comes in one pound spools. Two
Sporty's Pilot Shop ($13.95 each) . .
Eastwood ($10.99 each) . . . . . . . .
Lee Walden says, "If you're really looking for lockwire,
check out Harbor Freight Tools. If they sell the lockwire
pliers, they'll have the wire too."
Bill Frenchu suggests:
McMaster-Carr Supply Company
PO Box 440
New Brunswick, NJ 08903-0440
"Stainless Steel "Machine Grade Wire", "Lashing Wire",
"Lock Wire", "Tie Wire", "Spring Wire" and "Music Wire".
Most available in 1 or 5 lb. spools, in various diameters
from 0.009" to 0.125"." Note that the "spring wire" and
"music wire" will be very hard, just like the fishing leader
"Also Inconel Lock Wire in Silver and Black." Another
note: Inconel is what was used for lock wire at P&WA on
jet aircraft engines; it's really excellent and will not
rust, even though it's generally not as pretty as stainless
Small Parts Inc.
PO Box 4650
Miami Lakes, FL 33014-0650
"Precision ground Type 304V Stainless Wire, in 30 or 60
inch lengths, shipped "straight," not coiled. Diameters from
0.005" to .104"." Since it's shipped uncoiled, I'm betting
this is a hard alloy as well.
Michael Stanford says, "Monel is the alloy of choice for
siezing wire in most situations, it has the proper
combination of corrosion resistance, malleability and
strength. Stainless is generally too hard to be twisted
without breaking. Most stuff that is advertised as true
stainless is an alloy anyway, usually monel.
"An easy source for a small quantity is West Marine, a
catalog boat stuff company. 800-538-0775, a 30' roll of 20
Ga (0.037"), order #127854. They also have stores in most
coastal areas of the USA. Sailboaters use siezing wire for
safety rigging parts.
"Standard safety/siezing wires and the special tools to
properly twist/tension it are also available from Jensen
Tools, 800-426-1194. Jensen is expensive and caters to the
electronics industry. http://www.jensentools.com.
"The cheapest source is Northern Hydraulics,
800-533-5545, http://www.northern-online.com. Pliers are P/N
15646-C121 and wire is P/N 156461-C121, 365' x 0.032" dia.
roll of "stainless". If you don't already have the Northern
catalog, get one -- it is a valuable asset."
There is, in fact, a special tool made just for making
hose clamps from wire. This is not the same thing as
lockwire pliers; lockwire pliers merely twist two wires
together neatly. This hose clamp tool is designed to help
pull the wire tight around a hose before it is twisted. It's
sold under the names ClampTite or Clamp-It, and the claims
include that it can use wire to make hose clamps up to ten
times stronger than screw-type clamps. The Clamp-It is sold
in Australia by
Super Drill Sales
P.O. Box 393
Oakey Q 4401
+61 076 913 162 Fax: +61 076 913 076
Mobile: 018 878 782
FUEL SUPPLY CHECKING: It is often useful to know
if the fuel supply to the injectors is working properly. To
do this, Robert Dingli suggests installing a fuel pressure
gauge: "I bought a VDO fuel pressure gauge for about Aus$40
and connected it to the fuel rail where the cold start
injector was once supplied. I believe any pressure gauge
designed for hydrocarbons would be suitable and other brands
sell for much less. My gauge is mounted in the engine bay as
I am paranoid about high pressure fuel entering the
"There are a couple of things to note about connecting
the gauge :
- use high pressure fuel line and fittings.
- don't mount the gauge on the engine as vibration will
- use a restrictor in the line as the pressure
fluctuations will also kill the gauge."
FUEL ODORS: Jaguars seem to be prone to fuel
odors; the XJ-S was even recalled to provide a more positive
vapor recovery system. Please note that while Jaguars often
smell like fuel, they're not supposed to; it is an
indication of a problem, and should be addressed.
One excellent suggestion is to trot the car right down to
your local Jaguar dealer, or anyone else with the equipment
to test automotive emissions. The testing equipment includes
a probe that is inserted in the tailpipe to detect unburned
hydrocarbons (fuel). This probe is real handy for finding
fuel leaks anywhere in the car.
There is a relay in the trunk through which the EFI
controls the fuel pump. If you remove the relay and jump
connectors 86 and 87, the fuel pump will run whenever the
ignition is on. This is useful for searching for fuel leaks
without having to leave the engine running.
There are a couple typical places to check for sources of
odors. The fuel filter is the size of a Coke can and is
located behind the spare tire in the trunk. When this filter
is replaced, it is all too easy to spill its contents within
the trunk. The nature of the foam padding under the carpet
is such that once this happens, your trunk will smell of
fuel for all eternity. The only suggested fix is to replace
the carpeting and padding. It is recommended that before the
filter is replaced, and before any repairs to the fuel
system in the trunk are carried out, the carpet be
Possible locations for leaks include the fuel tank
itself, located over the rear axle. It is accessible by
removing the spare tire and some other stuff, then pulling
the carpet out. The tank sits on a thin pad. Meanwhile, on
the underside of the car there are numerous lines that are
held to the car with little clips and rivets. One of these
rivets is in the panel the tank sits on, and sometimes the
weight of the tank compresses the pad enough that the metal
tank contacts the tip of the rivet. After some vibration,
the contact can wear a hole in the bottom of the tank. Once
the tank is drained and removed, it is a simple matter to
patch the hole (there are types of epoxy sold that will work
well) and find an alternate way of supporting the item under
Officially, the recall supposedly was to prevent
excessive pressure/vacuum cycles on the tank, resulting in
stress cracks. Obviously, this is something else to check on
Chad Bolles reports that the seal around the rear
windshield starts leaking, and the water soaks the sponge
under the tank and causes the tank to rust.
The tank is connected to the filler cap with a short
piece of hose and some clamps, accessible from within the
trunk by removing some carpet. Another place to check for
As described above, there are several fuel lines that
include a piece of hose in the middle of a metal tubing
assembly. Despite the pressure, these hoses often weep fuel
rather than burst. One of these pieces of hose is in the
high-pressure line directly over the right rear wheel arch,
and is difficult to see because of some heat shielding.
Check all of these lines with the pump running, and replace
any hose you even suspect of being the cause of odors.
Derek Hibbs says: "The answer for my fuel smell was
simple, the fuel cap overflow pipe was disconnected and any
spillage during refueling was draining directly into the
boot/trunk instead of onto the ground. Reconnected the
overflow pipe and no smells (I also take more care when
Also check the components of the vapor recovery system --
FUEL TANK LEAK REPAIRS: If you have tank leaks due
to perforations, one good solution is to coat the inside of
the tank -- and it forever ends the concerns about rust
scale from the tank fouling the fuel pump as well. John
Whitehead says "I have used gas tank sealer from Bill Hirsch
Automotive, with great success. I put it in the fuel tank of
my '67 XKE which had a number of pin hole size leaks.
Previous attempts to coat the outside of the tank were not
as successful. The tank sealer is gasoline and alcohol
resistant. A quart can is sufficient as only a thin film is
coated to the inside of the tank. I am not sure of the
product's chemistry, but it dries to a white Teflon-like
film." Obviously, major cracks or holes will require more
FUEL COOLER: Many people see that the air
conditioning circuit in the Jag includes a fuel cooler, and
assume that this is a high-performance trick. Dragsters
often include an ice bucket in the engine compartment to
cool the fuel on its way to the engine to get more
It's a great idea, but unfortunately not the case. The
fuel cooler in the Jag is in the return line going back to
the tank. The pump moves much more fuel than is normally
needed and most of it recirculates. The fuel being heated
while passing through the engine compartment as well as the
pumping energy itself would eventually heat up the fuel in
the tank significantly, possibly causing vapor lock problems
and problems passing EPA emission requirements -- heated
fuel gives off more vapor. The cooler is to counteract the
heating effect. This may help explain why the ventilation
system has the A/C running during most conditions.
Why Jaguar doesn't put the cooler in the supply line and
reap both benefits is anybody's guess. Perhaps it's more
difficult to make a cooler to operate at the higher fuel
pressure on the supply side.
FUEL COOLER - CONVERTIBLE: According to Michael
Neal: "This vapor lock problem was such a problem that the
convertibles were modified to keep the A/C compressor
running all the time. The aerodynamics on the convertibles
caused the engine compartment to run even hotter than the
coupes. With the A/C compressor running the fuel cooler kept
the fuel temp to a decent level."
HOT STARTING: The fuel cooler works great when the
engine is running, but is worthless after the engine is shut
off. The heat rising from the engine heats the fuel in the
rail, which is not moving. If the engine is started about a
half hour after shutoff, it may have difficulty
Jaguar has provided two different fixes for this problem.
Both involve a temperature sensor in the boss on the left
side of the fuel rail; the boss has no opening into the
fuel, but the sensor has a copper bottom that presses
against the rail to sense the temperature. The boss itself
seems to exist on all XJ-S's, since a recall replaced the
rail after the hot fuel problems were found.
One type sensor has vacuum connections, and is connected
between the intake manifold and the left side fuel pressure
regulator. The other type sensor is electrical, and is
connected in line with the inlet air temperature sensor for
the EFI system.
FUEL COOLER - 1992-ON: Richard Mansell quotes from
a Jaguar publication that was sent to him: "It is titled
"Technical Guide - The New XJ-S 1992 Model Year Preliminary
Information". In it there is a paragraph about the fuel
cooler deletion, it says:
introduction of the in-tank fuel pump, the fuel cooler is
deleted. This affected the characteristics of the system
so that a muffler is added in the line to reduce noise
"I wonder why adding an in-tank fuel pump should allow
the deletion of the fuel cooler. It also says in another
As a result of the
deletion of the fuel cooler, it is necessary to introduce
a redesigned hot start system. The thermal vacuum valve
fitted to pre-92 MY vehicles is replaced by the following
1. Fuel rail temperature
switch. The electrically operated switch enables the fuel
rail pressure to be increased when the fuel temperature
exceeds 70 degrees Centigrade at hot starting.
2. 45 second timer
module. The timer limits the time for which the increased
fuel pressure is applied.
3. Solenoid vacuum valve.
This controls the vacuum signal driven by the fuel
temperature switch and the 45 second timer.
4. Vacuum delay valve.
This controls the way the extra pressure is applied at
hot starting to give a decayed reduction in fuel pressure
over 45 seconds, after which the pressure is switched to
FUEL PICKUP: The following tip was sent by Leonard
Berk of Howard Beach, NY: Apparently his XJ-S would run fine
when first started, but after a half hour it would start to
lose power, eventually coming to a stop. After shut off, it
would start and run fine for another half hour. After much
head scratching, it turned out the problem was dirt in the
small sump tank in the trunk. Apparently, as the engine ran,
the dirt would gradually collect on the screen on the pickup
and plug it. When the engine was shut off, the dirt would
fall back to the bottom of the tank.
There is another potential problem with this pickup
screen. It is a molded plastic item, and is installed by
simply sliding it onto the metal pickup tube until it
bottoms on a shoulder on the inside of the screen. The
shoulder is not very big, however, and the screen has been
known to get sucked on and over the shoulder until the
bottom of the screen meets the end of the pickup tube. This
reduces the effective area of the screen by about 80%, and
the screen will clog much more easily. To prevent this, put
a hose clamp or other obstruction on the tube for the base
of the screen to rest against, so that it does not rely on
the internal shoulder.
However, there is some experience to indicate that this
problem is often accompanied by a failed fuel pump. Perhaps
the plugged pickup causes the pump failure. Be aware that
when you find the pickup problem you may also have to
replace the pump before the car runs right again.
Apparently, if you can hear the pump whining when driving,
you can count on it. Perhaps the cost of this pump is enough
to justify checking the pickup before you have
John Goodman owns a 1989 XJR-S 6.0 litre: "I have just
cleaned out my sump tank, no signs of a filter!" Who knows,
maybe Jaguar decided it was more trouble than it was
Goodman also came up with a neat procedure for emptying
the sump so you can work on it. "What I did was to clamp the
fuel hose from the tank to the sump with some vice grips,
start and run the engine till it stalls which soon empties
the sump." Since the sump is vented, the pump can draw out
of the sump without drawing a vacuum. The pump draws the
fuel out of the sump and returns it to the tank; it would
empty the tank by itself if you can run the pump without
starting the engine.
FUEL PUMP CONTROL: On the Digital P system anyway
(I dunno about the D Jetronic), the fuel pump is controlled
by the EFI ECU via a relay in the trunk. The ECU contains a
circuit that determines whether or not the engine is
actually running and shuts off the pump if it has been
motionless for more than a coupla seconds. This is for
Unfortunately, this circuit is reportedly unreliable in
the 6CU, and sometimes will fail to keep the pump running
more than a coupla seconds regardless of whether the engine
is running or not. Typically, the starter is engaged, the
engine fires, the starter is released and the engine quickly
dies -- misleading the mechanic to believe that the problem
is related to coming off the starter circuit.
If you'd like to test this circuit to determine if this
is your problem, simply remove the fuel pump relay in the
trunk (the one without a red mark on it) and put a jumper
between terminals 86 and 87. This will allow the pump to run
whenever the ignition is on. If the car now runs perfectly,
the fuel pump circuit in the ECU (or the relay itself) was
the problem. AJ6 Engineering, as well as other places that
repair ECU's, should be able to fix this problem for far
less than the cost of a new ECU. If you're willing to risk
the odds that you will be in an accident where you are
knocked unconscious, a fuel line is severed, and something
ignites the leaking fuel, you can leave this jumper in place
FUEL PUMP NOISE: Noisy fuel pumps are a very
common complaint. Goodman suggests: "it may not be the pump
causing the noise, try the hose clamps on the fuel outlet
pipes from the pump vibrating against the boot floor or
battery stand. Fuel filter may be blocked causing strain on
the pump or the filter may be vibrating against the tank or
spare wheel, steel fuel lines vibrating under the floor
FUEL PUMP VARIATIONS: Goodman reports: "The latest
XJ-S's had pumps inside the fuel tank, so Jaguar may
have done this for noise related problems. I suspect that
these pumps are lower output because the '93 model XJR-S had
twin in-tank pumps, and must be ordered in a matched
& Eisenhardt Convertible
FUEL TANKS: This section is of no use to coupe or
later convertible owners, but it is reportedly difficult for
H&E owners to find information on how this system works
so a description is included here. According to Mike
Cogswell, "In order to make room for the folding top and its
mechanism H&E had to take the standard tank and cut part
of it off. It would appear they literally cut the tank and
welded in a sloped section. To regain fuel capacity, they
added a second tank under the parcel area, basically where
the rear seat would have been in a coupe. The upper tank is
about 14 US gal. and the lower is about 11.
"As you know, the standard tank has a sump from which the
high pressure fuel injection pump draws its fuel. Since the
second tank is lower than the first H&E added two
concentric hoses. The larger outer hose allows fuel to
gravity drain into the lower tank from the upper (which is
where the filler neck is located.) Consequently, the lower
tank is always full until the upper tank goes dry.
Meanwhile, a small submerged pump constantly pumps fuel from
the bottom tank to the top tank via a small tube that is
located in the center of the large drain hose. The fuel is
dumped into the upper tank's sump, where it is available to
the main fuel pump. The submerged pump can pump fuel faster
than the engine consumes it, but any in excess of the sump
capacity will drain right back into the lower tank. Both
pumps only run when the ignition is on and the standard pump
circuit is energized, so all the regular safety interlocks
"Each tank has its own fuel level sending unit. The upper
unit is apparently the standard XJ-S tank unit. The lower
one is similar, except the mounting plate is horizontal
instead of vertical. The two gauges are wired in series.
There is a small circuit board in the H&E harness that
theoretically turns on the low fuel level light.
"My gauge is wildly inaccurate. Because they are in
series I'm guessing that my top one basically hits bottom
well before the bottom one starts to drop. As a result, my
gauge is very non-linear."
Tim Blystone points out that since parking the car
nose-down on an incline will cause the fuel to drain toward
the forward tank and away from the sump, the auxiliary pump
might not keep up when the tank is less than half full. "All
of the early tank designs will stall on a sufficient
"H&E went through a couple of different
configurations. The main difference is the dams added in the
interior of Jags original tank."
FUEL HEATING PROBLEMS: The stock Jaguar fuel pump
moves far more fuel than the engine normally needs with the
excess returned to the tank. Since this heats the fuel
somewhat, a fuel cooler is included in the return line,
using the A/C freon circuit to provide cooling. On the
H&E, however, the problem is exacerbated by the fact
there are two pumps running full time, coupled with
the fact the car is a convertible so the top may be down and
the A/C off on warm days! Tim Blystone: "Normally
this presents very little problems until the A/C goes on the
fritz, or you have one of H&E's earlier designs. If it
is summer, the top is down... the AC system is off. No cool
fuel. Vapor lock from hell."
FUEL SYSTEM MODS: Tim Blystone: "My modification
puts the plastic hose from the H&E fuel cell directly
into the supply for the sump tank. A new and longer piece of
hose is required. Fuel is pumped by the H&E pump
directly into the Jag sump tank and bypasses the need for
the tank to be gravity filled. There is a return to Jags
original main tank from the sump tank so there is no excess
pressure in the sump. The result is a fuel system that
doesn't have the H&E problem with steep inclines or die
dead in the middle of a hot southern day."
GAS CAPS: The single gas filler on the H&E is
the same as the two on an XJ6.
VAPOR RECOVERY SYSTEM: When the car is running and
drawing fuel out of the tank, there must be a vent system to
allow air into the tank to prevent a vacuum from being
created. It is no longer acceptable to merely have a small
hole in the gas cap; such methods allow fuel vapor to escape
into the atmosphere all the time, whether the car is running
or not, and would contribute to air pollution. Now, unless
you live in California or somewhere else where they have
intelligently-designed gasoline pumps, you pump 20 gallons
of fuel vapor out into the air every time you pump 20
gallons of liquid gasoline into your car, and proper fuel
tank venting begins to look like an inconsequential issue.
But we will endeavor not to get into a discussion of the
real intentions of our legislative bodies.
Nowadays, the vent system from a fuel tank is connected
to a carbon canister. Air can flow freely through the
canister into the fuel tank, but when vapors from the fuel
tank try to escape through the canister they are absorbed by
the activated charcoal.
Of course, the charcoal can only absorb so much fuel.
Therefore, whenever the engine is running, there is a system
by which the engine draws fresh air through the canister.
This draws the vapors back out of the charcoal and burns
them in the engine.
When the car is not run for extended periods of time, the
amount of vapor generated in the tank could be considerable.
Gradual changes in ambient temperature and barometric
pressure would cause the vent system to "breathe", running a
large amount of vapors through the canister. To absorb all
this vapor, the canister would have to be prohibitively
To prevent this, there is a valve in the vent line
between the fuel tank and the canister. This valve will
allow air to flow in either direction, but only after a
certain pressure or vacuum has been reached. If the contents
of the tank expand and try to escape out the vent, it will
prevent any flow until the pressure reaches a set value, and
then it will allow it to pass to prevent damage to the tank
or hoses. Similarly, if the contents of the tank contract
and try to draw air in through the vent, the valve will
prevent any flow until the vacuum reaches a set value, and
then it will allow it to pass to prevent the tank from
collapsing. As a result, the vast majority of the smaller
expansions and contractions do not open the valve at all,
and the amount of vapor the canister is expected to absorb
is greatly reduced.
Of course, this means that at any given time the fuel
tank and hoses may be slightly pressurized, even when the
car is not running. Even the tiniest leak anywhere in the
system may become quite significant.
The carbon canister vent is an excellent system, does not
hurt the performance one iota (as opposed to some other
emission control systems) and is normally maintenance-free.
Activated charcoal can absorb and release fuel vapor
forever, it doesn't wear out or get "full". However, there
are filter elements within the canister (after all, it is an
air intake) that may eventually get clogged, and the carbon
itself may eventually get contaminated with fuel additives
or other non-petroleum substances, so it is recommended the
canister be replaced once in a great while.
If you're really a skinflint, the carbon canister
can be opened and the filters replaced. There are two, one
at the top of the charcoal and one at the bottom -- you must
dump all the charcoal on a newspaper or something. Both
filters can be neatly replaced with coffee filters. The
canister can be held shut with aluminum tape when
The carbon canister itself has an opening on the top to
atmosphere, and three fittings on the bottom. The fitting
labeled T is connected to the fuel tank, via the appropriate
valve and the vapor separator. The fitting labeled P is the
purge line to the engine. The fitting labeled C is capped
off; it originally was the connection for venting the float
bowls of the carburetors, but they are history. Note: if you
fit carbs, do not simply open this fitting and try to use
it; a screen has been omitted inside as well, and you will
draw carbon granules into the floats.
One of the possible causes of the common fuel odors is
the location of the canister in the XJ-S. On most cars, it
is located in the engine compartment where any escaping
fumes will simply be blown away by the flow of air through
the radiator. But in the location in the bodywork forward of
the left front wheel, there is no such flow. The vapors may
gather in the bodywork and eventually work their way to the
passenger compartment. Of course, there aren't supposed to
be any fumes escaping, so this is a secondary
problem. However, it might be a good idea to connect a
length of hose to the atmospheric vent on the canister and
route it out the bottom of the car.
Another possible failure mode is that the engine is not
properly purging the canister. If the engine is not drawing
air through the canister when running, the canister will
quickly become saturated with fuel and will cease to absorb,
and any further fumes coming down the vent line will escape
VAPOR RECOVERY SYSTEM -- AFTER RECALL: The
original XJ-S vapor recovery system pretty well followed the
description above. However, there was a tendency for the
tank to develop stress cracks from excessive pressure
fluctuations as well as indications it did not vent as well
as intended (including numerous complaints about fuel
odors), so there was a recall to address the system. In
general, the recall involved the installation of Rochester
valves in place of the pressure-operated tank vent valve.
Basically, a Rochester valve works the same way as the
earlier pressure-operated valve when the engine is off, but
when the engine is running a vacuum signal opens the
Rochester valve wide open to freely vent the tank. The
recall also installed a pair of vacuum-operated purge valves
to provide a positive purge when the engine is running. The
left side throttle butterfly housing was replaced with one
that had suitable taps for controlling the Rochester valve
and purge valves.
David Johnson: "The Rochester valve (Part CBC 7714) is a
cylindrical disk (approx 2 inch diameter) with an inlet from
the fuel tank vent pipe and outlet for the vent to connect
to the carbon canister. A third outlet at the top is to
connect to the manifold vacuum. This top vacuum pipe opens
the Rochester valve when the engine is running. Hence you
should not have pressure in the fuel tank when the
engine is running (If you do, check the Rochester valve).
The location of the Rochester valve is next to the carbon
canister under the front left wheel arch. The valve stops
the fuel tank from venting below 2 psi, (i.e. the valve
only opens above 2 psi on the fuel tank side), and
the valve opens due to a small vacuum on the tank side. That
is why you get a whoosh when the car is standing on a hot
day. A simple check is to open the tank cap after standing
for some time on a hot day. A huge whoosh and an oil canning
sound means the valve is not working -- the vent is
connected wrong, or the vent is blocked. If you have
no whoosh then the vent pipe or fuel tank is leaking,
and the car will either have a fuel leak or a fuel vapor
smell. It is important to disconnect the Rochester valve and
check it opens at 2 psi and under vacuum. Also note the
Rochester valve must be connected in the correct direction.
It all sounds complicated, but the system is simple."
For those who have disconnected the vacuum lines from the
butterfly housing and want to reconnect them properly, I can
give this guidance based on the dealer instructions for the
recall that installed the system in the first place: Among
the two vacuum hoses that go from the butterfly housing to
the area in front of the left wheel well, one is supposed to
have a black and white delay valve in it, hanging in the
vicinity of the coolant header tank. A hose from the black
side of this delay valve should be connected to the front
port on top of the left butterfly housing. The hose with
nothing in it should be connected to the rear port on top of
the butterfly housing. Of course, there were several
variations on this system as applied to different cars, but
I think that description should cover most of them.
VAPOR SEPARATOR: In the XJ-S, there are several
vent lines from the fuel tank. They all are routed to a
small vapor separator high in the bodywork to the right and
above the fuel tank. This small metal contraption is
intended to allow most fuel vapor to condense and drain back
into the fuel tank. The vent line to the canister is routed
from a point high in this separator, so fuel vapors must be
very determined indeed to make it past this point.
Note that the vapor separator has been blamed for many
problems. Since it is steel, it is prone to rusting. If a
hole rusts through it, fumes will be vented into the
bodywork. Also, rust particles may fall inside it and plug
the tiny vent passages and hoses.
VAPOR RECOVERY SYSTEM -- INCORRECT PLUMBING: David
Johnson owns two H&E's, and reports: "I found that on
both of my cars the fuel vent systems were plumbed
incorrectly (not done by my local dealer). The carbon
canister under the front left wheel arch is connected to a
vent pipe from the fuel tank, and a vent pipe to the PCV
valve next to the LHS air intake. The two vent pipes were
wrongly connected, i.e. the fuel tank vent was connected to
the valves for PVC pipe (two valves operated by vacuum from
the LHS manifold), and the PCV vent pipe was connected to
the Rochester valve that should be connected to the fuel
"So what's the big deal? Well, the valves that would
normally operate the PCV valve only open under vacuum when
the engine is running. When parked and sat in the sun
the tank cannot vent! I tested these valves with 10
psi and still the valves would not open. The tank is now a
sealed container with fuel vapor inside! There are only two
things that can happen:
(a) The tank will build up a severe pressure and
will rupture in time due to fatigue at the weakest
location. A pressurized gas vapor canister in my
car/garage does not give me a good feeling!
(b) If you are lucky, one of the vent pipe/fuel
connections will leak to relieve the pressure and cause a
fuel leak and/or a fuel vapor smell. I am still not keen
on this option with the car in my garage!
"If the tank is connected correctly to the Rochester
valve, the valve will open at approx. 2 psi to relieve the
pressure in the tank, and also opens under vacuum. This
stops the tank venting under all conditions and hence does
not overwhelm the carbon canister.
"Of course my vent works perfectly now, no gas smells and
no severe pressurization of the tank, just a small woosh
when I open the tank cap. I wanted to pass on this info to
others, since I consider this a dangerous fault, in this
case not a design fault but an incorrect installation by the
Jag dealers on two cars! Very ironic since the recall
was to solve this problem."
"This recall was Hess specific (recall (C002) XJ-S purge
kit (Feb 1990). If you check the recalls on XJ-S 86-91 you
will find there were similar problems with the regular XJ-S
but a different fix. The mod was estimated to be 4.35 hrs
for later Hess cars to install Kit JLM2046 and conduct a
fuel system integrity test.
"The diagram (figure 6, page 8 of 23) showing the valves
and carbon canister connections is not very clear because
the fuel vent pipe connections are only partly shown, but
the PCV pipe vent connections are clearly shown. I deduced
these pipes were incorrectly attached by testing all the
valves to determine how the vapor system functioned. I
called the Jag dealer the next day to get a copy of the fuel
vent recall, and hence confirm the connection was
"I do not think the two cars were fixed by the same
dealer for the recall. One car is from New York, and the
other is from California. That is why I suspect other cars
could also be connected wrongly!"
Linkage, Idle Speed Adjustment
IDLE SPEED ADJUSTMENT: On each butterfly housing,
there is an adjustment screw that a lever contacts when the
throttle is at idle. These are not to be used for
setting idle speed. If they have been disturbed, the linkage
must be readjusted.
Underneath the rear end of the left intake manifold there
is an aluminum housing with two hose connections; one that
goes up to the back end of the manifold and one that goes
forward to the air filter housing. Just below the connection
leading to the air filter housing is a bolt. This bolt,
believe it or not, is the idle speed adjustment. The bolt
itself obstructs an air passage, so the farther the bolt is
unscrewed, the more the passage is opened, and the faster
the engine idles. It's not real convenient to get to, but a
ratchet and a long extension with a swivel at the end will
do it. The bolt requires a 13 mm socket to fit.
AUXILIARY AIR VALVE: If you have tried to adjust
your idle using the above method and turned the screw all
the way in and the idle is still too high, chances are good
that your auxiliary air valve (also called an "extra air
valve" in Jaguar repair manuals) is stuck open. The
auxiliary air valve is in the same housing that the idle
adjustment screw is on, and is supposed to open when the
engine is cold to keep the idle up. To check to see if it is
the problem, remove the left side air filter cover and
element, start the car and let it warm up, and check how
much air is entering the hole where this valve is
Per Jan Wikström: "It's a particularly dumb design,
unfortunately, being a slide valve - one tiny speck of grit
or a modest accumulation of soot and it jams, and if your
engine boils, the wax bulb that operates it can expire. You
can overhaul these valves, though. When you look down the
neck from the top, you'll see a part with about six holes
(there are variations) in it; that's the actual valve. If
you make up a tool with six flat-ended pegs to pass through
these holes (about 2in long, from memory) you can press out
the brass bulb unit in the bottom - carefully; the pegs need
to be as large as you can fit through. You can now clean out
the bore and the valve slider and press the bulb back
Mike Morrin: "On my car, the auxiliary air valve was
stuck in the closed position, which caused the car to stall
when cold. My method of disassambly of the auxiliary air
valve was different: I mounted the valve in a lathe with the
thermo bulb away from the chuck. I then carefully skimmed
metal from the bottom of the aluminium housing until the
thermo bulb dropped out. This made the housing about 5mm
shorter than standard. I then fabricated a plate from 5mm
aluminium which had the same mounting holes as the valve
body, but a hole in the middle which was a snug fit for the
thermo bulb (and too small for the flange in the bulb to
slip through). After freeing up the sticky valve, it was
reassembled with its new spacer plate and a good dollop of
silicone sealant and has given no problems since."
OVERRUN VALVES: If the throttle is closed at an
elevated RPM, the manifold vacuum can exceed that normally
found at idle. Under such high vacuum conditions the
fuel/air mixture being introduced into the cylinders, even
at the proper ratio, can be so rarified that it cannot be
reliably ignited with an ignition spark. If that cylinder
full of unburned mixture is then exhausted, it dumps quite a
load of raw hydrocarbons into the atmosphere. However, as
Roger Bywater points out, an even worse result (from the car
owner's standpoint) is what happens when the mixture is
later ignited within the exhaust system; it can blow the
mufflers open. This igniting within the exhaust is what
causes the "backfire" upon deceleration that is
characteristic of some cars -- mostly pre-EPA cars.
The little housing at the forward end of each intake
manifold contains the overrun valves. They are a
spring-loaded poppet valve that should be adjusted to open
when the manifold vacuum is higher than a set amount more
than idle vacuum. Basically, this limits the manifold vacuum
to a level where ignition is reliable. It also tends to make
the engine feel as though it has no "compression" on
deceleration -- basically, the throttle is being opened a
little. In fact, on some other automobiles, the same effect
is achieved by physically opening the throttle.
Unfortunately, Bywater reports that the springs in these
valves get weak with age, and the valves may start opening
at idle. This causes a high idle, and often erratic. If you
remove the housing and look at the valve, you can see it
would be very easy to adjust -- but what do you adjust it
to? Basically, adjust it just tight enough that the valves
are closed at idle -- which can be confirmed by putting a
finger over the hole in the filter housing with the engine
idling. Bywater says, "Setting the over-run valves by
checking with finger over the hole is as good as any method.
As long as they don't leak at idle but work when you blip
the throttle and release it to create an over-run condition
they will be OK. You will probably hear them anyway.
Actually they only lift a few thou and should be set to open
at about 20" mercury."
ACCELERATOR PEDAL -- EARLY MODELS: Mike Morrin
says, "The Jaguar pre-HE service manual seems not to have
been updated from 1975 to 1981, which is fine for my car,
but I have seen a few things which are obviously wrong for
most of the pre-HE cars. A minor example of this is the RHD
accelerator pedal assembly: The only type shown in the
manual was only fitted to the first 200 cars."
BUSHINGS: There is a
throttle shaft on each side of the engine, parallel to the
heads, that transmits throttle motion to the butterflies.
The rear end of this throttle shaft, along with some
linkage, is supported by a plate bolted to the rear of the
intake manifold. There is a rubber bushing in the plate for
the shaft to turn in. This bushing is probably shot --
British nonmetallic parts again. This bushing will dry up,
crack to pieces, and fall out, leaving the throttle shaft to
wallow around in the opening. In fact, this is another
example of a 100% failure mode in the XJ-S; if you haven't
already replaced the bushings, they are probably bad right
now. The effect on the throttle operation is not good, as it
tends to screw up the sync of the two butterflies with each
other and with the throttle pot in the bellcrank. There are
also reports that this problem can have adverse effects on
emissions tests, especially if one bushing is gone and the
other is still on the job.
The part number for the original Jaguar rubber bushing is
C34388. However, I don't think anyone in their right mind
would recommend the original bushing -- it's rubber, for
heaven's sake. Rubber throttle linkage bushings are a relic
from cars with rigid linkages from the pedal to the carbs;
since the engine moved around on its mounts, some means had
to be provided to connect the pedal on the car to the
butterflies on the engine without the engine's motion
affecting the throttle position. The solution was to have
one rotating shaft with one end mounted on the car and the
other mounted on the engine; the pedal was connected to a
bellcrank right next to the mount on the car, and the
butterflies were actuated by a bellcrank next to the mount
on the engine. The pedal twisted the shaft which opened the
butterflies, and engine motion would rock the shaft back and
forth without twisting it. Rubber bushings were needed at
the ends of such shafts to isolate engine vibrations from
the rest of the car, and to allow the small angular motions
of the shaft without any binding.
None of this applies to the XJ-S. The motion of the
engine relative to the car is dealt with via a throttle
cable. The linkages where the bushings are used involve
shafts that are mounted at both ends from the same intake
manifold, so there is no relative motion. Totally rigid
bearings will work fine.
This application really begs for nylon bushings, but
bronze bushings would probably work just as well if you can
install them so they wouldn't rattle or jingle. The shaft is
5/16", and the hole in the plate is 1/2". With a little
looking, it should be possible to find a suitable generic
bushing to use here. A bushing with a single lip will work;
retention won't be a problem since it is effectively
Most auto parts stores carry replacement nylon bushings
for a Chrysler windshield wiper linkage that can be made to
fit, but it requires quite a bit of cutting since the OD is
too large and must be cut down. It also has a closed end and
an anti-rotation tab that must be cut out.
Replacing this bushing looks difficult; it appears to
require removing either the throttle body or the linkage
support plate, either of which is a pain. You may choose to
remove the linkage support plate, since it will permit you
to fiddle with the bushing installation away from the car --
or take it with you when shopping for a bushing.
David Littlefield describes a shortcut: "I was able to
replace both my bushings today in my '88 XJ-S without
removing either the throttle body or the linkage support
plate. I first loosened the pinch bolt on the short rod that
is between the bushing and the throttle body. I then removed
the spring clip that holds the spacer that fits against the
bushing. By sliding both the spacer and the pinch bolt as
far as I could towards the front of the car, I was able to
gain enough clearance to push the rod towards the rear of
the car for the ball end of the rod to come out of the
throttle body fitting.
"Once I had the rod out of the car, I was able to move
the pinch bolt even further back-- past the knurled portion
and right against the shoulder. I then took the new bushing
to my bench grinder. I carefully ground down almost all of
the lip on the beveled side. I put the bushing on the rod,
then fitted the rod back in the car, pushing the rearmost
end in first and then putting the ball end in the throttle
body fitting. I then pushed the bushing into place, while
still on the rod. Removing almost all of the beveled lip on
the bushing allows the bushing to be pressed into place
while on the rod, since distortion of the inner diameter of
the bushing is minimal. Replacing the spring clip behind the
spacer and resetting the pinch bolt completes the
"As stated in the book, a bushing with a single lip will
work since the bushing is effectively trapped. There are no
real worries about the bushing slipping back on the rod
because the spacer and spring washer hold it in place.
"I used the factory bushing for this procedure, but I see
no reason why it wouldn't work with others." Littlefield
gets two demerits for replacing a British nonmetallic part
that failed with another part just like it -- but at least,
using his method, it won't be too difficult to replace them
Jeff Elmore offers a different shortcut: "I
remembered someone saying that it was easy if you did
(something) and slid the shaft back through the throttle
housing. Well, after some contemplation, I figured he meant
removing the screws from the shaft-to-plate and sliding the
plate out of the shaft and sliding the shaft forward through
the housing. Well, it worked like a charm and the bushings
were replaced in about 20 minutes."
If you'd like to try a more expedient fix, John Napoli
describes a method he credits to Gerry Duff: "We just cut a
couple of pieces of rubber hose. Slipped right onto the
shafts, and is the right OD. No tools or disassembly needed.
Been working fine for almost a year, and when they wear out
5 minutes to do it again. When the repair was done, the
rubber hose sections were left long enough so that they
could be turned around if excessive - and quick - wear was
realized until a more conventional repair could be effected.
Last week I asked the owner how it was holding up. He pulled
the hoses, and stated that there was no visible sign of wear
at all -- he had never needed to turn 'em around." Note:
this author tried using this method on a friend's car, and
couldn't get it to work. It apparently requires a particular
type of hose we didn't have on hand; we were trying to use
fuel hose, which was a little too fat to fit through the
hole properly and tended to "walk" off the shaft when the
throttle was moved repeatedly. Napoli suggests that the hose
used with success may have been vacuum hose.
As Leslie Winfield discovered, a generic bushing with
no lip will work if you can figure out how to hold it
in place -- and can make installation almost as easy as
Duff's fix. "I purchased a 1/2 inch x 5/16 inch bronze
bushing 1 inch long, and two 1/2 inch outside snap-rings. I
ran a 5/16 bolt through the bushing, pinched it with a nut
& chucked it in my drill press (poor man's lathe). I
shaved about .005 inch off the OD with a flat file, used a
hacksaw with a 24 tpi blade to cut a groove about 3/32 of an
inch from each end deep enough for the snap-ring, and then
cut the bushing into two halves. With a little fiddling, the
snap-ring can be threaded to the inside of the support
plate, the bushing can be slid over the shaft and through
the hole in the support plate (grooved end first), and the
snap-ring positioned into the groove on the bushing. The
bushing is now captured on the shaft, and almost no play is
observed with this setup. It doesn't look too bad, cost
$1.07, and it should last as long as my '79 XJ-S does." Of
course, if you happen to have purchased bushings with a
flange, you can still use this method by cutting the groove
in the opposite end from the flange. While buying these
bushings, you might want to buy a spare one in case you ever
need to replace the thingy in
your Lucas distributor.
After bushing replacement, the linkage should definitely
be adjusted as described below.
ADJUSTMENT: If the butterfly
stop screws have been disturbed, the linkage bushings have
been replaced, or any other tinkering has been done that
could mess up the linkage adjustment, it should be
readjusted. I'd like to simply dump this description off on
the repair manual since any decent repair manual would
provide a step-by-step procedure that's easy to follow, but
unfortunately the procedure described in the Jaguar XJ-S
Repair Operation Manual (Section 19.20.11 followed by
19.20.05) is only barely discernible and the one in the
Haynes manual (Chapter 3, Section 47 followed by Section 37)
is bloody awful. So, I will endeavor to explain the process
here more clearly.
There are four distinct adjustments, which must be done
in order because each affects the others.
First, disconnect the crossrods from the throttle pulley
by prying them off the ball joints, and remove the air
filters. Loosen the locknuts and turn in the butterfly stop
screws until they don't interfere with the butterfly motion.
Open a butterfly, insert a feeler gauge between the
butterfly and the housing, and let the butterfly close on
it. What size feeler gauge? Well, therein lies a question.
The earliest Jaguar repair procedures specified a 0.004"
(0.105 mm) gauge, but after 1978 it was changed to a 0.002"
(0.05 mm) gauge. In theory, it shouldn't be too critical;
the change may have been made because some of the thicker
feeler blades were too stiff to bend to the shape of the
throat, and held the butterfly too far open. The 0.002"
gauge probably would work fine on all cars. Some have
suggested a piece of paper works best. Whatever, with gauge
in place, adjust the stop screw until it just touches and
tighten the locknut. Repeat for the other butterfly.
Second, loosen the clamp on the lever at the rear end of
the butterfly shaft, directly below the crossrod attachment.
Allow the spring to hold the butterfly against the stop, and
hold the crossrod attachment ball joint in the idle
position, where it contacts its own stop. Take up all slop
in the butterfly shaft coupling (adjacent to the butterfly
stop) in the opening direction, and retighten the clamp.
Repeat for other side.
Third, connect the crossrods at the outer end only, and
offer up the other end to the pedestal ball joints. The
lengths should be such that the sockets can line up without
moving anything. If not, loosen the locknuts on the
crossrods and adjust accordingly.
Fourth, loosen the locknut on the full throttle stop
screw on the throttle pulley, and back the stop screw away.
Hold the pulley in full throttle position, noting that the
butterflies are both full open. Adjust the stop screw until
it just touches the pulley and retighten the locknut. This
stop screw merely prevents stress on the linkage while the
engine is at full throttle and the kickdown switch is in
operation, and is not meant to restrict full throttle.
Ensure that the throttle moves freely through the full
range of motion. Note especially that if the cruise control
cable is too tight, it can restrict the throttle linkage
moving fully to idle.
You will need to warm up the car and readjust the idle
speed, since the butterfly stop screw positions have been
THROTTLE STICKING: Apparently, all cars have
occasional problems with throttle sticking due to buildup on
the butterfly itself. A butterfly cleaning procedure from
Randy Wilson: "You are cleaning the throttle plate and
surrounding area. The edge of the butterfly and the area of
the housing right around it will be covered in black goo.
Prop the throttle open and wipe the stuff out with a rag.
Use the weakest solvent you can to get it clean. I start
with a "WD-40" grade oil, and go to carb cleaner if it's
really bad. Oven cleaner is out. Sand blasting is not needed
"Warning: Some non-Jag cars, notably later Fords, have a
teflon coating on things in an attempt to reduce this
problem. Most solvents will damage this coating."
THROTTLE LINKAGE LUBRICATION: Jan Wikström
says, "The ball-joints shouldn't be lubricated at all,
unless you want to give them a dusting with Teflon or
graphite. The reason is that grease hardens and oil or
grease picks up dust from the air, increasing linkage wear
The Fuel System