Jaguar XJ-S. Service manual - part 70

 
 

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The people at John’s Cars (page 715) say they will test your ECU for you, free of charge.  They are confident you will 
eventually be buying something.  They add, however, that since testing requires a car, there may be a few days’ delay 
until they have a car with the correct system on hand for the testing. 

Of course, you can probably learn a lot yourself if you have a friend with a car similar to yours.  Swap the ECU’s and 
see how many problems go with them. 

If your ECU gives up the ghost, please see the comments under Performance Mods (page 309) before spending the 
major $$$$$ for a new one.  Also, you might want to contact AJ6 Engineering listed on page 710, or Corsaro 
Electronics on page 704. 

If you wish, you can open the ECU easily enough; it is a simple cover-body-cover sandwich with several screws 
holding it together.  Note that a couple screws have aluminum caps that serve as a tamper indication; it might be wise to 
inquire about policies regarding exchanging an opened unit before opening. 

Take precautions to avoid static electricity discharges while inside this unit.  Usually, it is sufficient to keep one hand 
on the chassis while working. 

 

EFI WIRING HARNESS TROUBLESHOOTING:  Matthias Fouquet-Lapar suggests “one thing I would do is to put 
in fixed resistors for the various sensors direct at the ECU connector” to find out if there’s a problem in the harness. 

 

INJECTOR CONNECTORS -- D JETRONIC:  The connectors on the early cars are a simple plug that inserts into a 
rectangular recess on the injector.  If you need new connectors of this type, Ed Sowell says you can get them at NAPA. 
 “They have what they call "harness rebuild" parts which is a selection of connectors and pigtail wires with various 
connector styles.  You buy the connector body and the pigtails separately, and assemble.  Be sure to ask for "harness 
rebuild parts," as you will get nowhere asking for injector connectors.  The NAPA numbers are: 

 

housing  2-17411 (this is the plastic connector body) 

 

contact  2-17421 (this is the pigtail with the connector attached-- 2 req'd per connector) 

Also discovered that NAPA has the contacts themselves without the pigtail wires.” 

Tom Simon says, “I have located a source for the injector connectors for pre-HE engines.  They were ordered from 
Fuel Injection Corporation in California.  Their web site is 

www.fuelinjectioncorp.com

.  The connectors are part 

number 920155B; they are black rather than the original white.  The terminals with no wires are 920121B.  They also 
have the boots (920125B) for the connectors.  I ordered 20 connectors, 14 boots, and 50 terminals. The total order 
including shipping was less than $35.00.” 

 

INJECTOR CONNECTORS -- DIGITAL P:   Apparently Bosch decided the simple rectangular plug wasn’t secure 
enough, so they developed a much more sophisticated connector for the Digital P system.  These connectors are a 
rectangular hard plastic box that fits around the connector on the injector, and they have an external spring to provide 
snappage.  These connectors simply pull off, although they can be a real bear sometimes.  It might not be a bad idea to 
apply a little grease or something to that spring or the little point that it snaps around to help get it off next time. 

These same connectors are also used on the Digital P temperature sensors. 

According to Peter Cohen and others, NAPA offers this connector in parts or as an assembly.  The assembly, with 
pigtails hanging out, is part number 2-17424.  In parts, the numbers are 

 

Housing  - 4 per box 

 

 

2-17416 

 

Spring Clips - 25 per box   

 

2-17417 

 

Terminal Ends - 25 per box  

2-17418 

 
 

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Michael Bucklew says, “The NAPA parts did not fit due to the lip around the bottom that holds the spring clip.  My 
plugs do not have the lip around the bottom.  The NAPA parts were $14.49 each for the plugs.”  It’s unknown if 
Bucklew’s comments apply to the pigtailed assembly, the individual parts, or both, but at that price who cares?  That’s 
too much. 

Rue Palmer says the problem is that is apparently the wrong NAPA part number.  The connector you need is NAPA 
part number 2-17427.  He describes this as a “Wired Housing (a wired connector minus the spring clip).  I had to use 
the spring clips from the old injector connectors because the new connectors don't come with them.” 

Lucas lists the parts this way: 

 

housing  526 8917 

comes in packages of four 

 

contact  526 8918 

comes in packages of 25 

 

spring  526 8930 

comes in packages of 25 

The Lucas parts, as would be expected, fit fine; this author used them on my harness rebuild. 

It appears that the complete connector with pigtails is the most common way to find these parts.  Discount Auto Parts 
also carries Caltherm, item number 08653, “GM Multi-Port Fuel Injector Connector”.  Costs less than two bucks each. 

Cohen:  “Other vendors are: 

 

Conduct tite:  Fuel Injection Repair Socket    #85850 

 

Dorman:  Connector kit 

  #643-463” 

John Robinson adds, “Beck Arnley makes an OEM copy connector w/pigtail: 158-0017.” 

Ed Forman says, “I looked at several parts stores, found some that looked like they would work at an Auto Zone store.  
But the back stuck out too far and hit the plate that holds the injector in place.  In desperation I went to a Jag dealer, 
they had the same type as the Auto Zone store.  But I found the right ones at an Auto Value store.  They are made by 
Parts Master part # 84059, they work great.  About $3.00 each, that's better that $12.50 at Jag.” 

Patrick MacNamara says, “Best deal I have found on the injector connector housings is from Del City.  They were only 
$1.03USD each and are complete with 6" pig tails, #73522.  No boots though.”  MacNamara ditched the pigtails since 
he wanted to use high-temp wire, which meant he needed terminals separately:  “The terminals for the injector housings 
are available from your local Volvo dealer at about $.75CDN each (Cable terminal #V0978258-2).  The terminal 
connectors from Volvo are nifty two piece quality looking terminals and don't look as cheap as the ones installed by 
Del City with their pigtails.  They have the double OEM crimp with one on the insulation and one on the actual wire 
which if I understand correctly should negate fatigue.  The terminal crimp part seems to be referred to as an open barrel 
arrangement necessitating special crimping pliers.” 

So, Patrick, why didn’t you get the housings from Volvo as well?  “I had purchased one to trial fit it to the Jag injector. 
 They are of a superior design in terms of positive locking with a nice button for release as well as being made from 
what looks like high impact resistance plastic.  Unfortunately the button release and lack of half moon cut out negates 
the fit onto the angled injector port.” 

None of the above items seem to include the rubber boot that covers the joint between the wires and the plastic 
connector.  Gregory Wells says, “Wurth markets the rubber boot and as with all Wurth parts, they're expensive.  I think 
the Wurth part number is 5-7120, but I'm not real sure of that.  Wurth distributes hardware and shop supplies to repair 
shops via independent salesmen and as far as I know does not distribute to the retail market, so if you want to chase 
these down call import repair shops to see if Wurth calls on them.” 

Rue Palmer says you can get the boots from NAPA:  “Harness Boots (for those who want the original rubber boot- 2 
per box):  2-18414” 

MacNamara adds, “Boots are also available from Volvo at $1.84CDN each (Housing cover #V0967340-1).  These fit 
the Del City Bosch connectors very well but are slightly shorter than the Jag OEM ones.  They are also much sturdier 
looking.” 

 
 

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If you can’t find the boots, screw it; the harness will work just as well and just as long without them, and probably look 
just as good or better.  Keen Young says, “My solution was 1/2" shrink tube over 1/4" shrink tube.  Put them both on 
the wires, solder on the connector, slide the small tube up to the connector, slide the large tube over the small one and 
over the connector, heat.  If you look really closely, you can tell it's not factory.  Got the tubing at the local surplus store 
for $.20/foot.” 

It’s also apparently possible to upgrade this connector.  Since it’s used on so many types of car and has been for so 
long, it’s to be expected that companies have come out with improved versions.  Mike Waldron says, “Autotronic 
Controls, makers of MSD Ignitions (

http://www.msdignition.com

), make weatherproof (don't need no stinkin' boot) 

connectors for Bosch style injectors.  These are designed to be removable from the injector, thus they don't break!  The 
part number for a bag of eight is: 2400” 

Unfortunately, Tom Bennett says, “Nice connectors, only problem is they do not fit!  The lock/unlock mechanism gets 
in the way with the injector hold down.  Nice for the other sensors though.”  Hmmmm; sounds like the ones Forman 
found at the Jag dealer. 

Robinson, who works at Bosch, says, “Delphi/Packard Electric makes a great connector that I believe will fit: 

 

15305086 - connector body 

 

12176636 - terminal 

 

12176807 - seal 

 

15326238 - spring 

“These are for the new GM eco-tech V6 wire harness.  Anybody who carries AMP products should be able to get 
them.” 

You could just drop into a junkyard and buy a bunch of connectors; lots of cars use Bosch injectors and most of them 
don’t cook them like Jags do.  Guy Poppe says, “I gathered 12 from the junkyard from GM cars.  Nice and sturdy and 
clip on -- great.  The connectors are too big as they strike the mounting plate.  Tried a Chrysler connector from my '94 
LHS and they fit.  They look different than the GM or Jag ones but again better quality.” 

 

INJECTOR CONNECTOR REPLACEMENT:  In case you’re trying to keep straight which wire goes to which side on 
each injector, Keen Young says, “No polarity.  The injector doesn't care which side is ground (earth).” 

Bill Farnsworth:  “Last month I changed all my plastic injector connectors without removing the existing leads.  I 
replaced all 12 connectors in 3 hours.  Knowing a bit about connectors and wiring kinda helped too.  Here is how I did 
it: 

“Tools required: 

Small flat blade jeweler's screwdriver 

Small utility or x-acto knife 

Hot air (750w) heat shrink gun  

A three foot length (appr.) of 1/2 in" shrink tubing 

1 Tube silicone glue/sealer 

“Remove the connector from the injector.  With the utility knife cut away the existing heat shrunk rubber from around 
the base of the connector leaving enough to maintain a base of rubber against the connector.  You will notice that there 
is a small amount of epoxy glue holding the rubber to the base.  Work the rubber and connector back and forth (like 
snapping a crab leg) until the glue releases.  Turn the connector toward you and inside you will see a small slot above 
each  lead.  Insert the small jeweler's screwdriver into the slot; this releases the tab holding the lead to the connector.  
You can pull the lead out now.  If it doesn't release, work the screwdriver around until it does release.  Or you can just 
break the old connector off; it's toast anyway. 

 
 

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“What you have left is a clean wire with two leads, and a 3" length of Jaguar rubber boot, all intact.  Neat!!  If the leads 
aren't clean, now is the best time to clean them with alcohol. 

“Now, slide a 4" or 5" length of 1/2" shrink tubing over the leads and boot.  The tubing has to be long enough to go 
over the entire boot and cover both ends by at least a half an inch to prevent water seepage.  Next put a small amount of 
silicon glue/sealer around the base of the boot that meets up with the base of the connector.  Be careful not to get any 
sealer on the leads. 

“Now take the new connector and push the leads thru the end until they seat.  The base of the connector with mate up 
perfectly with the boot and the glue will seal up the end of the connection (just like original). 

“Slide the tubing up and over the boot and over the base of the connector until it clears the lip by the same distance as 
the original (look at the next injector connector).  Take up your heat gun (a hair dryer might work, but probably doesn't 
have enough directional control.) and warm up the shrink tubing until you have a perfect fit around the connector and 
boot and wiring at the other end.  Take care to not melt other wiring in the area.  Aluminum foil works as a good heat 
shield/deflector.  Move onto the next injector.  The first one will take you a while.  Once you get a feel for how 
everything comes apart and goes together, then the whole process will take you 5 minutes per injector.” 

 

IS YOUR INJECTOR HARNESS COOKED?  Surprise, surprise.  Craig Sawyers explains:  “As some of you will have 
found, the insulation on the wires under the hood gets really brittle with time, and cracks.  I was just browsing the 
Farnell catalogue (major electronic component supplier), and their selection of "automotive cable" uses PVC insulation, 
with a maximum temperature spec of 70°C.  Interesting, think I.  In fact, most PVC insulation conks out at 70°C.  Some 
special UL-rated cable goes to 90°C (or 105°C if it won't be moved while it is hot, some hope on an engine).  So it is 
practically guaranteed that the insulation will fail on a Jaguar, even if it doesn't overheat!  This is particularly true of the 
V12, where both major engine harnesses run smack down the centre of the V.” 

Is this a serious problem?  It’s just cosmetic, right?  You don’t care except the wires look bad, right?  Well, ask Rue 
Palmer, who had a sudden loss of power and immediately pulled over and opened the hood to see what was the matter: 
 “It looks like one of power wires in the injector harness shorted out due to the PVC wire insulation becoming brittle 
and cracking, which then melted most of the insulation from the wires to the right bank injector harness.  It appeared 
that when the harness shorted it caused all the injectors in the right bank to go to a continual spray condition which 
flooded out the right bank and dumped raw fuel into the exhaust system.  Upon examination the next morning, both the 
right exhaust and the engine oil had gas in them.  

“Additionally, gas sprayed into the engine compartment caused by the injector located at "5 A".  It had a hole melted in 
the housing of the injector body.  None of the fuel lines appeared to have been damaged but I replaced them all anyway. 
 To this day we don't know why we didn't have a massive engine bay fire.  The wire in some places was glowing when 
we lifted the hood.  I don't think the fire extinguisher that I carry would have put it out if it would have ignited.” 

Funny thing: the only reason Palmer pulled over that quick is because he had read this book, and thought he was 
experiencing the Marelli failure described on page 160.  His car doesn’t have Marelli ignition, though, which was the 
first clue that this problem was different. 

Half the wires in the injector harness are connected to 12V power, and the other half go to the resistor pack and then on 
to the ECU in the trunk.  If any of the latter half short to ground, 12V power will be applied continuously to an entire 
bank of injectors.  This will flood out the bank, but worse it will cook wires and melt injectors because these circuits are 
not designed to have 12V on them for longer than a couple of milliseconds at a time. 

Still, reports of this cause of engine fires are not common -- which makes sense, actually.  Once the fire starts, all the 
insulation in the V will be burned away and the wires scorched, so it will be impossible to diagnose this cause.  Palmer 
is probably an extremely rare case for having caught it before ignition. 

Sawyers:  “It wouldn't be so bad if they had been routed along the fuel rails.”  Actually, this is fix #1 -- relocating the 
injector harness before it gets cooked.  This author moved it off the bottom of the V and up just an inch or so, fastening 
the harness clips under the intake manifold nuts rather than under the bolt heads holding the valley cover on.  This gets 
it out of the oil deposits and keeps it a lot cooler without changing the appearance of the engine significantly.  If you’re