Jaguar XJ-S. Manual - part 60

 
 

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Two of the hoses that need attention are not in the trunk, but rather under the car and over the rear suspension.  The line 
over the right rear axle is the pressure line to the engine, and the line over the left rear axle is the return line to the tank. 
 If the hose section of either line develops leaks, it seems to cause odor in the trunk more than anywhere else for some 
reason. 

Check all of these lines with the pump running, and replace any hose you even suspect of being the cause of odors.  
Better yet, just replace the hose sections if they are older than ten years or so. 

Both hose sections over the IRS are actually fairly easy to replace.  Both lines connect at threaded fittings at the forward 
corners of the trunk floor, and both have couplings just forward of the IRS.  Before removing the right side one, 
depressurize the fuel system, and before working on either, pinch the appropriate fuel lines in the trunk and in the 
engine compartment (if the tank hasn’t been removed and the system totally emptied). 

This author found the one on the right side a bit easier to do than the one on the left, because there were more other 
things in the way on the left side -- but some of these things, like the handbrake cable, may switch sides on a RHD car 
so others may have different challenges.  On the author’s ’83, the fuel line assembly on the right side came out as a unit, 
so it could be rebuilt and reinstalled easily enough. 

The line on the left side takes a little more thought.  First, there is a plastic clip up at the top of the arch holding it in 
place.  If it’s not broken to begin with, it’s easy enough to break it; it is only too apparent that it’s not necessary to hold 
it in place.  Second, the short section of metal tubing on the rear end is hook-shaped, so it isn’t likely to feed out over 
the IRS.  Instead, after disconnecting both ends of the line, pull it rearward a bit and use a razor knife to slice through 
the hose itself.  Then remove the rear section rearward and the front section forward. 

To rebuild and reinstall it, start by cutting a piece of new hose a couple of inches longer than the original hose.  In fact, 
note how much of the straight section of the hook-shaped metal portion is exposed beyond the end of the hose, and cut 
the new hose longer enough to cover almost the entire straight section.  Install this new hose on the front metal section 
of the line with an EFI clamp, making sure that the screw portion of the clamp is positioned downward and a little 
inward because the top and outer side will be against the inside of the bodywork.  Stick a plug in the end of the hose, 
then feed the hose into position from the front until the end of the hose comes out on the back side of the IRS where 
you can get ahold of it.  Clean the entire straight portion of the hook-shaped section in preparation for having a hose 
slid onto it.  Put an EFI clamp over the tube, remove the plug in the end of the hose, then push the tube into the hose 
and continue to push until things begin to line up.  Loosely assemble the coupling at the forward end.  When the tube 
has been pushed into the hose far enough that the threaded end lines up properly with the fitting on the trunk floor, 
position the clamp near the end of the hose and tighten it down.  By using a longer piece of hose here, the clamp is 
located such that it can easily be tightened below the corner of the chassis and the screwdriver can be held within the 
wheel well. 

When you tighten the threaded end into the fitting on the trunk floor, you will need to have an assistant hold the end of 
the line on the inside of the trunk in the correct position.  Failure to hold the lines in position while tightening will result 
in distortion of either the hose over the IRS or the hose in the trunk or both. 

 

COMPRESSION FITTINGS:  In the author’s ’83, there are seven places in the rear end of the car where a metal fuel 
line is attached via a brass nut and a brass compression seal.  Three of these are on the main fuel tank itself: the main 
line to the surge tank, the vent line from the surge tank, and the return line from the front of the car.  The other four are 
in two elaborate bulkhead fittings where the supply line and the return line run through the floor of the trunk. 

These fittings are assembled by sliding the nut onto the tube, then sliding the brass compression seal onto the tube, then 
inserting the tube into the fitting and tightening down the nut.  As the nut is tightened, the brass ring is compressed onto 
the steel tube, forming a reliable seal and also securely holding the tube in place.  Typically, the thin-walled steel tube is 
soft enough that the compression of the seal necks the tube, although this isn’t strictly necessary for sealing or retention. 

The bad news is that these type connections are meant to be assembled once and left alone.  If you unscrew the nut, you 
can remove the nut/tube/seal assembly out of the fitting, but you cannot get the seal off the tube -- and you’ll only get 
the nut off if it can slide off the other end.  If you simply slide the thing back together and tighten it down, there’s only 
a moderate chance it will seal; the tube and the compression ring apparently work-harden, and there’s no further 

 
 

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compression available to allow it to reseat.  Applying sealing substances is a waste of time, and can result in chunks of 
sealant plugging up your fuel system.  To ensure a proper seal, both the brass ring and the steel tube must be replaced 
whenever such a fitting is disassembled. 

The good news is that the brass compression seals themselves are common in the US and are available at any hardware 
store or industrial supply house.  They are also often available in auto parts stores, in the bins with brass fittings.  Note, 
however, that there is a similar type of compression seal intended for use with copper or plastic tubing, and the 
compression ring itself is a bit different; it has a collar around the middle.  It might work here, but obviously you might 
be well advised to seek out the same type as was originally used to ensure it seals properly in these fittings. 

Suitable steel tubing is also available in sizes up to 3/8”, sold in auto parts stores in straight lengths with flared ends and 
nuts in place; just cut the flares off and chuck the nuts, they won’t work here, all you want is the straight length of 
tubing. 

You can purchase a tool in any auto parts store that will help you bend metal tubing without crimping it.  Note that 
cheap tubing benders often don’t work very well; it is recommended that you spring for a good one.  Also note that 
you’ll want to put the bends in your tubing before you cut it to length. 

You can make a barb for attaching a hose to the steel tube using a tool sold at most auto parts stores.  It’s called a 
“double flaring tool”, and its purpose is to make those flared ends that you just cut off the tubes you bought.  The 
intended use of the double flaring tool involves two steps.  The first step forms a little bulb on the end of the metal tube, 
and the second step folds the outer end of this bulb back inwards to form the double flare.  Forget the second step, just 
perform the first step, and it leaves a neat, professional-looking barb on the end of the tube for attaching a hose.  One 
example of this tool is the AmPro T73360. 

Anyplace that sells the compression seals probably also sells the nuts that are used with them -- but that won’t help you. 
 This is a Jaguar, so the fittings are some oddball thread.  In the US, you’d go nuts (!) trying to find a new nut of the 
same thread; if you need a new nut, just go ahead buy an entire new hose assembly from Jaguar.  Fortunately, the old 
nuts are usually reusable; just cut the old tube in half to recover them. 

When you assemble a compression fitting with a new section of tubing and a new compression seal, you’ll know what 
they are supposed to feel like.  You can feel a smooth crush as the seal is compressed onto the tube. 

Now that you’re an expert in rebuilding those compression fittings, let’s discuss some special cases.  First, the Rube 
Goldberg bulkhead fittings going through the floor of the trunk: if these things are leaking, don’t even think of trying to 
reassemble them with new compression fittings and new tubing.  Instead, yank the entire contraption out of there and 
install a simple rubber plug to fill the hole in the trunk floor.  Cut a hole through this plug the size of the steel tubing 
involved.  Bend a piece of steel tubing to a suitable shape and insert it through this hole, and connect the hoses to each 
end of it with suitable clamps.  Presto, a simple, logical fuel line assembly with minimal opportunities for leakage. 

“If it ain’t broke, don’t fix it” is a good credo, but you could actually justify removing those bulkhead assemblies on the 
basis of the weight savings alone. 

I’d suggest you throw those bulkhead fittings as far as you can, but remember to save the nuts from them first; they 
might actually fit two of the connections on the tank itself  -- although that’d be an unreasonable expectation from the 
British, they probably deliberately made them different to make sure you couldn’t connect the wrong line to the wrong 
place! 

If your problem is that you’ve boogered up one of the smaller nuts threaded into the tank itself, you might be able to 
save yourself the trouble of trying to find such an oddball nut by simply performing this bulkhead fitting replacement 
and getting the nuts from there. 

Finally, the big problem: the main line from the main tank to the surge tank.  On the author’s ’83, this is a hook-shaped 
1/2” tube that screws into a 90º fitting on the tank.  I certainly hope they changed this design on later cars.  The 
incompetence of the designer was so awe-inspiring that you can’t even get a wrench on that nut without removing the 
tank from the car!  Anybody exhibiting this level of skill should be operating a broom rather than a pencil -- and only if 
you’re not too picky about how clean the floor is. 

 
 

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This fitting is the most likely one to be leaking because of the hook-shaped tube.  Getting a hose connected to that tube, 
maneuvering the other hoses in the area, even replacing the battery or getting the spare tire in and out is liable to apply 
some stress to the end of the hook, all of which is likely to bend the tube right at the fitting and cause the compression 
seal to start leaking. 

So, once you finally figure out this is where your trunk odors are coming from, you need to get that fitting apart.  Drain 
the tank (see page 244).  Disconnect the straps holding the tank in place.  Insert some sort of broad pry bar between the 
gas tank and the deck it’s sitting on and see if you can lift the tank up a bit.  If you can’t, use a machete to slice through 
the foam under the tank so you can.  Once the tank is liftable, it’s actually possible to get a box end wrench on the nut 
by sliding it on from the other end of the hook-shaped tube and holding the tank lifted as you maneuver the wrench to 
the nut and turn it.  Hence, you can fix your leak without totally removing the tank, disconnecting all those other lines, 
removing the battery tray, etc. 

1/2” brass compression seals are actually not too difficult to find, but 1/2” thinwall steel tubing is.  The auto parts stores 
only carry steel lines up to 3/8”.  You might try a place that carries parts for large trucks.  Other places that may carry 
1/2” steel tubing, including hydraulic shops, typically have thicker-walled tubing -- which will work fine in the 
compression fitting but is difficult to bend or to form a barb on for connecting the hose. 

The solutions here come together.  First, you don’t want to install another hook-shaped tube.  Instead, what you want to 
do is install a very short straight tube, providing a hose barb right there at the fitting on the tank.  Then you can use a 
longer piece of 1/2” fuel hose to connect it to the surge tank.  Hence, you probably already have the tubing you need -- 
in the old tube.  Just cut off the old compression seal and cut off the hook end, leaving a straight section of steel tubing 
about 3” long.  Apply the old nut and new compression seal and install.  Be sure to clean up the outside of the section of 
tubing with some fine sandpaper so it forms a good seal. 

Of course, if you try to use the double flaring tool to provide a hose barb on a tube this large, you may mess it up -- and 
you have no backup tubing.  Solution: don’t bother providing a barb here.  The maximum pressure this hose will ever 
see is about 3 psi, nowhere near enough to push a clamped hose off a smooth tube. 

If your hook-shaped tube is too messed up to obtain a clean straight section from, you can use thicker-walled tubing 
since you’re not bending it and you’re not forming a barb.  The thicker-walled stuff might even be advantageous in 
providing a more secure attachment with more resistance to bending or deformation. 

 

STINKY FUEL LINES:  Believe it or not, one reported cause of fuel odors in the trunk is apparently the use of the 
wrong type fuel hoses.  They’re not leaking; the odor seeps through the material of the hose itself.  You can tell this is 
the problem by wiping your finger on the surface of the hose, walking a few feet away, then smelling your finger.  If it 
smells like fuel, that’s the problem. 

 

 

Fuel Lines 

 

FUEL HOSE MAINTENANCE:  If you have any doubts about the condition of the fuel hoses in your car, replace 
them.  Based on experience from the online discussion list, it would be an excellent idea to replace all of the fuel hoses 
in the car at least once every ten years; you can do it every five years to be on the safe side. 

In some locations, there is a fuel line assembly that consists of hose crimped onto metal lines; in such cases you can just 
buy new Jaguar fuel line assemblies, but it’s cheaper to buy generic hose and install it in the existing lines with suitable 
clamps (see below).  The hardest part would be getting the original crimped fittings off, but the second time you do the 
job it’ll be easier since you’ll only need to loosen clamps.  Don’t overlook the sections of hose in the lines looping over 
the rear suspension on each side of the car. 

 
 

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In other places, you will be replacing pieces of hose with clamps on the ends.  In yet other locations, you may need to 
replace hoses that don’t seem to be attached at all -- they are merely pressed onto the fitting.  Please read the following 
sections to understand how these work before tackling the job. 

 

FUEL HOSE SIZES - D-JETRONIC:  Bernard Embden found that the nipples on the D-Jetronic fuel rail are 
measurably smaller than standard 5/16” nipples.  “Putting 5/16" hose on the Pre-H.E. fuel rail resulted in a less than 
satisfactory connection.  The clamps had to be tightened excessively and bunched the 5/16" hose just to prevent leakage 
at the required 30 lbs. fuel pressure.  Even in this unsatisfactory condition, the 5/16" hose could be rotated easily on the 
rail.  I fitted the 9/32" hose.  This was the only size hose that fit the nipple correctly.” 

 

FUEL HOSE SIZES - DIGITAL P:  The D Jetronic fuel rail and injectors truly need 9/16” hose, a fairly unusual size.  
The original hoses on the Digital P fuel injectors appear to be 7mm or 9/32” as well -- but in this case it’s the wrong 
size.  The injectors themselves are made by Bosch -- and have barbs designed to fit an 8mm hose, a very common size. 
 The barbs on the square-tubing rail and on some of the lines to and from the rail are also designed to fit an 8mm hose.  
When you have the old hose off, it is a simple matter to measure the diameter of the straight-sided portion of the barb 
between the ridges to confirm what size hose is needed.  5/16” is 7.93mm and will fit an 8mm barb just fine. 

The problems begin when the novice mechanic finds out how easy it is to push the new hoses onto these barbs.  They 
just slide right on.  That just doesn’t seem right, and smaller hose is purchased and crammed onto the barbs with great 
effort and sometimes even boiling the hose prior to installation or other extreme measures that are only too likely to 
damage the hose or shorten its life. 

Resist such thinking.  The hoses are supposed to slip on easily.  Why would Bosch design an attachment scheme that 
requires lots of effort on an assembly line?  When 5/16” or 8mm hose is used on the clampless connections on the 
XJ-S, they simply do not leak.  There is no problem there; the fuel leaks the car is plagued with come right through the 
hose when it dries up and cracks. 

Some people have found 8.5mm hose -- sometimes at a Jaguar dealer.  Don’t use it on the XJ-S; there are no fittings on 
this car that call for this oddball size. 

 

FUEL HOSE TYPE:  The XJ-S features Electronic Fuel Injection, and EFI systems operate at higher fuel pressures 
than carburetors did: 30-50 psi vs. 5 psi.  Ordinary “fuel hose” was designed for 5 psi -- do not use it anywhere in this 
fuel system.  Most auto parts stores now carry “EFI hose”.  It is more expensive, but a fuel fire is no fun.  The basic 
generic EFI hose looks like standard hose; you will need to read the printing on the rubber surface to know you’ve got 
the right stuff.  Look for either “EFI” or “Fuel Injection” or some such clear indication of its suitability for fuel injection 
systems, or for a working pressure rating higher than 100 psi. 

If you have clampless hose connections (see below), generic EFI hose will work fine -- but there is yet a better idea.  If 
you find an industrial hose distributor or hydraulic hose shop, they can sell you what they refer to as “push-on hose”, 
hose that was designed specifially for these type connections.  Push-on hose is available in two different styles:  smooth 
rubber surface or cloth surface.  They both have basically the same specs; in fact, nobody seems to know why anyone 
would choose one over the other.  It probably has something to do with abrasion resistance or some such. 

The rubber surface push-on hose usually has a bunch of markings on it, including a pressure rating in the order of 350 
psi, but it probably does not use the term “EFI”.  There is a spec number on there, and you’re supposed to look it up in 
reference books to determine suitability for particular applications.  It is suitable for automotive EFI systems. 

The cloth surface hose this author found has far less text on it.  Duh!  It’s harder to write on cloth!  The letters are really 
big to be readable, and all it says is “WEATHERHEAD 5/16 H10005 D 09/14/98”.  The pressure rating on this hose is 
actually lower than the rubber surface hose (250 psi) even though it looks a lot tougher than the rubber surface hose.  
You cannot squeeze this hose flat with your fingers.  Weatherhead H100 series hose has a nitrile inner liner suitable for 
use with non-oxygenated automotive fuels.