XJ6 died on a short drive

XJ
21

Con,
From your picture it appears that your car’s Prior Owner, or his shop, made some wiring modifications to the wiring to your ignition switch and covered them with electrical tape. I highly suspect that these wiring modifications may be causing your fuel injector problems especially because that White-Yellow wire provides an important signal to the EFI ECU. I personally would not drive that car with those kind of shoddy looking splices and recommend that you get a new replacement switch right away. The Jaguar part for the ignition switch is DAC1607.

According to the Jaguar Series III S57 Electrical Guide (a very handy document to have) the Purple-Green and Purple-White wires are part of the Seat Belt Warning buzzer system. It looks a prior owner disabled it by disconnecting these wires.

The DAC1211 is the Power Resistor that provides the ground to fire the fuel injectors when the EFI ECU commands them to fire. The Series III XJ6 Parts Catalogue is a very helpful document to own when trying to sort out parts and part numbers and the DAC1211 is found on page 2G07.

I have found that the S57 Electrical Guide, the Parts Catalogue, and the two owners manuals (the green one and white one) are all worth their weight in gold as far as taking a lot of the mystery out of working on these cars. I would not be able to keep my three Series III saloons running without them.

Paul

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Ideally, the injector should be tested with an injector test light, Con - to verify ‘pulsing’. But also use 15W test lamp to identify whether there is adequate power as proposed earlier…

If the above quote is correct, Con - the ECU doesn’t trigger, ‘ground’, the injectors. I did not see that before Aristides quoted it? It is then relevant then to check the ECU grounding, pin #5.

Another wire, #1, white/black wire is connected to coil negative via the injector resistor pack. This wire conveys the triggering pulse, ‘grounding’ from the ign amp. Check coil neg connections; there should be 3 wires - black/white from ign amp, black/white to the ECU and one white/slate blue to the tacho. There should be 2 white to coil neg…

That the engine quit cold while driving adds spice to the problem - which is knotty enough already. That you have spark (strong, blue?) and the coil neg/ground test lamp flickers while cranking implies that the ign amp (a natural suspect) is working. Nominally, the ECU is less sensitive to ign amp malfunctions than the ignition system. You ‘cannot’ have ignition and no ECU triggering with an iffy ign amp - so the connection, coil neg to the ECU, becomes ‘interesting’…

While crude; disconnect ECU white/black at coil neg and, with ign ‘on’, repeatedly, rapidly touch and break ground. Nominally, this may trick the ECU to trigger the injectors every third time. If it does; ECU and wiring is OK, and the ign amp is under suspicion.

If it does not; ohm (ign off) between the (disconnected) wire and ground. It’s an improvised test - and I haven’t the foggiest idea of what it should read. But you may draw on your own expertise?

However, if you read ‘1’, break, there may be an actual wire break - or the ECU does not, by design, ground the connection at its end. You can back up by measuring resistance between the coil end and the resistor pack (indeed the item shown in your post) connection. And proceed in steps with the three connection points, coil end, resistor pack and #1 on the ECU connector…

You may also turn ign ‘on’ and measure voltage on the (disconnected) ECU wire at the coil end. A voltage reading can (theoretically) only come from a powered up ECU - but ‘no reading’ may be inconclusive…

In short; if there is proper power to the injectors - the problem is failure of the coil neg trigger to reach the ECU. Either wiring or no trigger from the ign amp - or, however unlikely, an ECU fault…

Frank
xj6 85 Sov Europe (UK/NZ)
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23

Hi Paul, Yes I have noticed that there are several wires in similar condition in that area. From what I can see it looks like there may have been some sort of security system installed that has been removed. There are several cut wires from a small wiring loom in the same area. They are not connected anymore and I have also found a wireless door locking module under there as well. I’m not sure at this point if this is part if the same secuirty system or not. I do have several of the books you mention but they are of the .pdf variety and to be honest I think I am old school when it comes to books, I think I’d prefer to have a hard copy rather than a copy on screen. In any case the Electrical Schematic reproductions in the .pdf manuals are not of a very good quality almost making them unreadable. I will investigate a replacement switch but at this stage, the car was running ok before the current crisis so will try to check all the connections there and get it going first.
Thanks for your input, I really appreciate all the informed help and advice I am getting here,
Con

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Wow…mamma mia.
I haven’t known how to respond, but i have looked at these images several times!

Just wonderful…better than new.
Who says the v12 can’t look great within the engine bay?

I’ve had 2. An '88 H&E convertible and a '90 coupe with Aston Martin wheels. Still in the gallery here, which is nice as I haven’t any idea where my photos of it are.

I removed air pump and rail on both to clean things.
I too am a perfectionist. Appreciate all out in the open actually as Jaguar had done.

Your cars are testament to how they can be.

Here ib Dalkas, tge highways are enormous, like airplane runways.
They are perfect car for here.

BUT I decided on an old S1 xj6 for personal reasons. Perfect car, blend of classic yet very modern. The prices often ridiculous yet that’s changing now.
Very difficult to find decent one.

Also, an xk motor is easier to maintain, i said…
Less expensive, i said…
Better gas mileage, i said…
If i need to pull motor someday i could, i said…
Parts more plentiful and less expensive…well, that’s sort of true. But not really, parts are easily sourced when u know what’s what.

In the end, well none are really true…and I’m ending up doing all on this one where none would be necessay on a well maintained xj-s.

And in the end spending as much or more on properly maintained xjs.
But I’m happy with my choice.

So nice to be at that point where all you need to do is maintain…

Anyway, thanks for sharing!
It would be nice to see everyone’s cars.

Kind regards
PS: You really let your wife drive the other?? Whew. Anorher reason i’m not the marrying type i suppose!

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Good point raised, and your electric nous will come in handy…!

As an aside, Con - if the injector test lamp stays fully lit with ign ‘on’, it means that that injector’s wire to the ECU is permanently grounded…

The ECU cannot influence the injector - it clicks opens and stays open, and should spray continuously while the pump is running…

Frank
xj6 85 Sov Europe (UK/NZ)
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26

You will get there Demian. I love driving our XJ6 - many can’t believe it’s 46 years old. Paul

1 Like
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Hi Frank,
I have ordered a Noid light so am waiting for it to arrive. I am finding I am in a real predicament at present. I think I am attacking this car all wrong. It clearly has several undeclared faults that have been there for some time before I purchased the vehicle. Every time I try working on one problem I seem to either find or introduce another. At present I can not even get the motor to turn over so now I need to trouble shoot the starting system. I put the battery on charge overnight, reconnected the battery and all I get is a click at the starter relay. Sheesh! :scream: Think I’m gonna take a break until the NOID arrives in a week or so. Thank you all who have contributed so far, I will take this thread up again in a couple of weeks when my head is a little clearer.
Con

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Sorry to hear all your troubles Con…
One step at a time and eventually you will sort the car out.
I have spent countless hours undoing all the “good” works that various useless mechanics have done to my car… and when they put their hands on the electrics “electrickery” gets a whole new meaning.
And in a sense, it’s better that all these problems present themselves now instead of somewhere in the Australian desert !

The process of elimination is the best way to deal with this kind of problems.

Take the big ECU plug out and with your VOM check that each pin connects to the corresponding sensor or component according to the diagram. What you are trying to find out is if the wiring is intact and you have no breaks and no shorts.
For example, the Air Temp Sensor pins are #20 and #21.
Measure the resistance at the sensor and then at ECU’s plug, it must be the same with just a couple of Ohms difference.
Check that every pin that is supposed to see 12V sees 12V, same for ground etc, to make sure that ALL pins are seeing what they are supposed to.
Once done you will know your wiring is OK and can be crossed of the list.

Your Ignition Switch is indeed a bloody mess Con…
Don’t run to get a new one before you see what is wrong with this one.
There are extra cables added. What do they do and where do they go ?
You must undo all that is done there…

Unplug the Switch, and same same, check that every wire connects to the wire it’s supposed to in every of the switch positions.
If something is wrong the switch can be opened and most probably fixed.
Once the switch is crossed of the list go to the next step.

If with a freshly charged battery you still have the same problem see if all pins at the starter relay get what the supposed to get, it could be a loose wire or the starter itself, give it a whack and see if it comes to it’s senses.
It’s a relatively simple circuit and easy to troubleshoot.

Sorry to sound pessimistic, but the NOID light will only confirm that your injectors are not firing… and you know that already.

Borrowing a known working ECU and seeing if the problem still exists would cross a big candidate of the list.

Bon courage,
Aristides

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29

Con,
I also prefer the hard copy technical documents for my Jaguars and purchased them on eBay. The S57 Electrical Guide was part of a dealership technician training package in three ring binders, the Service Manual a hard copy and of course the green and white owners handbooks are hard copy.

Shorely after I purchased my 1984 XJ6 Vanden Plas in 2000 I was on a trip about 100 miles away from home when my car mysteriously died all of a sudden. Thankfully I was in a hotel parking lot at the time, but it could have easily died on a freeway or while turning at an intersection in heavy high speed traffic. After it died thecar had a combination of “cranks but doesn’t start” and “doesn’t crank” symptoms with strange things happening with the dashboard lights as I tried numerous times unsuccessfully to get the car started and failed. After a long and expensive 100+ mile flatbed tow truck ride home I figured out what happened. The prior owners and their shops hand installed an aftermarket security system and mobIle phone by splicing into the ignition switch wiring much like I saw in your picture. The insulation on the ignition switch wires was melted and when I removed the ignition switch and disassembled it I discovered that the internal nylon parts were also melted and no longer holding the contacts together. I purchased a new ignition switch, removed all the non factory systems and their wiring, and then repaired the damaged wiring in the car with solder and shrink tubing. Since I completed those repairs I have been rewarded with many trouble free driving miles in this car.

Whenever I see strange electrical issues mentioned on this list, like yours, along with pictures of spliced and taped ignition switch wiring I automatically suspect a failed ignition switch and quite often (but not always) I am correct. If I were you I would remove the ignition switch and test it thoroughly outside the car on a bench to verify that it always works as it should in the various positions and inspect repair as necessary all the wires with solder and shrink tubing if before reinstalling it.

Before you trust that ignition switch again you should be certain that it works properly and won’t fail on you at the worst possible moment.

Paul

1 Like
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Thank you both Aristedes and Paul. I was feeling rather overwhelmed yesterday and when the car was not cranking it was alsmost the last straw. Of course you are both right. I need to work in a logical manner. So I think I will spend some time removing the security system wiring and also the keyless entry system. Then I will remove the ignition switch and replace with a good unmolested one.
I have been checking resitance on the ignition wires and finding quite high resitances for what should be simple straight lengths of wire. The black/white wire that goes from the coil -tve to the ECU when measured from the coil the the first multimeter plug just behind the block is showing 27 ohms which seems a bit high for a piece of wire less than 1m long. All of the wires around the coil, amplifier and fuel injectors are quite hard and cracked in places so I am seriously thinking about replacing these wires. Is this a “done thing” or do people just buy a new loom to suit? Money is not my friend at present so making it myself is preferred.
Aristedes, I do realize that the NOID lamp is not going to show me any different than I already know but I like to have the right test gear where possible.
I have also discovered that I have gained a fuel leak that is happening whenever I cranking the motor. It looks like it is below the intake manifold so will need to invest in some good wheel stands so that I can get underneath and find the leak. I suspect that this is a product of loading and unloading the car from the flatbed truck back when this all started.
So the beat goes on :smile:
Con

31

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Getting it to crank is the priority, Con - probably simple, at least to identify the problem…

The starter relay is triggered by white/yellow from the ign key, and just connects relay brown to relay white/red - which is connected to the starter solenoid. Which drags the starter pinion into mesh with starter ring gear - and connects the starter to the battery…right…?

Just for the record; just verify that the battery shows 12,7V or more…:slight_smile:

A dismantled alarm system is the pits; unless it is properly removed and the original wiring restored (fat chance) a botch makes fault tracing an uphill battle - as Paul’s experience demonstrates. Adding that the botch job may be perfectly innocent. Installing unavoidably ‘messed up’ the wiring - and without the original specs there is no way of knowing how it was connected up…

Use the starter relay connections as a test bed for jumpwiring from batt pos. 12V in relay white/yellow bypasses the ign key - and the relay should click. No ‘click’ implies a defective relay. 12V to relay white/red bypasses the relay - powering the solenoid, which sure should be audible. If so, and the engine doesn’t turn over - it’s a different ball park.

The finer points is of course to verify voltage; on white/yellow in ‘crank’ signifying the ign key is working - though it does not mean that it is in good working order. And on white/red when the relay ‘clicks’ - indicating that the relay is working…

That the engine quit during driving may be irrelevant to the ‘no crank’ problem - two separate issues. Certainly, the unknowns of the alarm system sure adds spice (tabasco!) to your endeavours - whether or not it is involved. Just make sure that eventual repairs are done properly - and complies with original wiring…

The ‘noid’ simplifies some testing, and can be used downstream for deeper probing - but get the thing cranking first…

Frank
xj6 85 Sov Europe (UK/NZ)
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As Frank said, getting the car to to crank is the first on the list Con.

I think you answered your own question… these cables are long gone !

Definitely DIY job and the electric diagram is your best friend here.
A used loom might not be much better from what you have in your car already.
Buy cables, terminals, shrink wrap and you are ready to go with minimal expense.
Take notes on everything you modify so you can retrace it in the future if you have to.
A very good source:

(no affiliation)
They have everything electronic you will ever dream, very good service and wholesale prices.

Highly recommended:
whenever you have a chance change ALL fuel hoses. (noticed the bold lettering?)
Injectors, Supply and Return.
Use Fuel Injection Hose in all, and CARB approved preferable - SAE J30R9
And don’t forget the ones in the trunk/boot. There I used Gates Barricade Low Permutation hoses to avoid unwanted fuel smells.
The only ones that usually don’t seem to have a problem are the 12mm ones from the tanks to the pump (also quite hard to find).

Keep us posted.

Best,
Aristides

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Went to work on the Beastie again and tried cranking. Not expecting much but surprise, surprise it cranked away happily, but of course did not start. I will start removing the security system wiring as soon as I find some time and also source a good ignition switch. I am also going to replace the ignition system wires and also a length of the signal wire from the coil back to the bullet connector and possibly back to the first connector block. Can anyone tell me how to connect the new wire so that it goes to the existing wire in the connector block. Is it a cut and solder to the wire coming from the connector or is there some other trick I should know.? I still need to check the wire all the way back to the ECU so may need to replace the whole run.
Con

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I trust the resistances were measured with wires disconnected, Con…?

Generally, wire resistances should pretty close to ‘0’ on lowest ‘ohm’ settings - or something is amiss. The wires are dimensioned for the expected current carried - and fused accordingly…

Test lamp is a prime test to ensure power is going to where it should…

Frank
xj6 85 Sov Europe (UK/NZ)
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35

I would send the bullet connector to the bin and replace it with a spade terminal plug.
Otherwise, cut and solder is the only other way.

Aristides

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Hi Frank
Yep pulled the Spade terminal from the coil and pulled apart the bullet connector then probes at each end. 25 ohms. The wire is cracked all along it so long overdue for replacement.
Con

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Hannclasdics,
I agree that the ignition switch is the likely source of some of the problems but there are probably more issues there. We should know more once Con replaces that.

Paul

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Con,
When I fix something I want the fix to last. In my opinion twisting cut wires together and covering them with electrical tape is not a lasting fix. I hate fixing the same thing more than once, particularly electrical wiring. I have spent many hours rebuilding engine bay electrical harnesses in my Jaguars. The heat, chemicals, and actions of prior owners and their shops took their toll on some of my Jaguar’s engine bay harnesses.

I try to reuse what I can, particularly the connectors, remove any damaged wire, and solder new appropriate replacement wires one by one with shrink tubing and then finish it off with high temperature 3M vinyl tape. I avoid using crimp connectors, particularly the colored ones, because the don’t look appropriate and I don’t believe that they will last. I solder all connectors. I have found the new fuel injector connectors at various autoparts stores. I have also kept all the wiring from two Series III XJ6 parts cars that I completely stripped so I have an ample supply of most connectors to harvest electrical components from when rebuilding the harneses. If you have access to a local junkyard you should consider visiting it in case you discover bits that are not reusable.

Paul

2 Likes
39

quick question to those who might know will a ignition switch from a 1980 S3 fit in a 1985 S3? The circuits seem similar.

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With that resistance it is ‘disconnecting’ wire, Con - not a connection for current…

…and since the ECU is basically analogue, current is required. Methinks that it may explain the lack of injector action - and a why not test it with a temporary wire, before doing it permanently…?

Frank
xj6 85 Sov Europe (UK/NZ)
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