A little late for this, But could the oil switch for the light or the other for the gauge have anything to do with an instant shut down?

 

Hello Anziobridgehead. I have been reading this thread and I haven't seen you answer any important questions. First off, do you have spark? Do you know how to check for spark at one of the spark plug leads?

Take the easiest spark plug wire to get at off at the spark plug, put a spare plug in the wire, ground it to the engine and have someone crank it, you should have strong spark. If no spark is present then disconnect the lead from the coil to the distributor at the cap, hold it near an engine ground and crank the engine. If you have spark there the distributor has an issue. If you still have nothing then keep tracing backwards.

If you have spark at the plug leads, then you have a fuel issue. If you have pressure at the fuel rail then the signal is not getting to the injectors. Follow Grant's advice here.

It is important that you let the people who try to help you know exactly what you have tried and what the results are. Don't leave any information out. Everything helps.

Good luck.

 

Big W, after reading over this thread, you're correct, I haven't really answered anything, and I apologize. I have spark, and as I checked the CTS, it crumbled. So i replaced it thinking that was the problem, and when I went for the module, the new one didn't seem to have proper grounding lugs. Then there was the wire out of the amp. So after a couple of sprays of ether, it fired up. I'll be buying some coaxial wire in the morning and spending an entire sunday slowly running a new wire to the amp. I'm sure I'll have a few more questions on that procedure.

 

Grant, You mentioned joining the thin wire and wrapping it, and then the coaxial cable, and then soldering. Could you give me a little more detail on how you would join the cables, also where would you solder? If it's the thinner wire that seems to be the culprit, should I be replacing just that thin wire or both? I appreciate as much input as possible. A thorough explaination will NOT insult my intelligence. I'm here for help so please " ASSUME I KNOW NOTHING". Thanks.

 

OK,

Sunday morning, fuzzy, so a STRONG coffee to to clear the thoughts HAHA.

That Jaguar coaxial cable needs to be carefully opened. It will have a black outer casing, under that is the Copper shielding, under that is a White/Clear core plastic, inside that core is the "thin wire" I mentioned.

I usually go over on the RH side, near our brake booster, which gives me a nice pliable section of coax.

Peel it back, get that coper shielding right out of the way (it is connected to earth at the ECU), and carefully open the White core, thus exposing the inner thin wire. This is NOT scary, just the first time jitters will strike.

Do the same with the new piece of coax, and join the 2 thin wires, and solder accordingly. I had some of that "heat shrink tape" which has a glue substance inside, and wrapped a small length around that White core, incorporating the thin wire repair, and heated it, sweet. I then joined the Copper shielding, and a drop of solder, and seperately wrapped that with the same heat shrink tape. Once I was convinced that NO strands of wire were going to interfere with that inner thin wire, I wrapped the whole repair with tape and heated again.

The connecting of that thin wire at the amp is fiddly, so look a few times at it, and make the repair, and ensure that Copper shield is NOWHERE in sight. It is earthed at ONE end only, and that is nearly always at the ECU.

Some years later I moved my "magic box" to the radiator front panel, alongside the ign coil, and did away with that coaxial cable in the engine bay totally.

Any more questions etc, ask away.

 

After cutting open the protective "sleeve", I found 2 wires. A black wire, and a white wire. When I stripped the white wire, it had a wire mesh coating over another white wire that was the thin wire that plugs into the module. The black wire was a single wire inside. That was soldered to the mesh coating, just before the module originally. If I strip the mesh off the white wire and join it to the new mesh wire and do the same with the thin wire, I still have a black wire not connected. I believe this needs to be soldered to the mesh shielding. Where should I solder the black wire?

 

OK,

The black wire is the shielded wire in an extended form that may have been attached to an earth point AT the amp, although I am only aware of that mesh/shielding being earthed at the ECU, but as long as it is attached to earth at ONE end only is fine.

The White is the thin wire in question.

My strong suggestion id to get a DVM, and unplug the main ECU plug, and do a continuity test of the thin wire. Pin #18, and the bare section under the bonnet, thus establishing the integrity, or lack of, in that thin wire. A long wire to reach the boot will be needed. If the thin wire tests OK, then it is deemed OK in my book.

Then do the same test on the shielding simply by earthing one probe, and poke the other probe onto the open mesh under the bonnet. If a continuity is found then it is attached at the ECU, so insulate it in the bonnet section, ensuring it is NOT contacting that thin wire in any way, if not, then attach the black wire to an earth point at the amp. the plug will need to be plugged into the ECU for this test, or do it prior to unplugging for the thin wire test.

I have attached a wiring diagram that should assist, and a "word" paper on the pin outs from the ECU, and where they go.

I will look thru my library of diagrams for the one that shows the wires at the ign amp and post them as soon as i find them.



XJ-S ECU Pinout table.doc

 

OK, found it.

Item #12 is the amp.

The rest is self explanatory, and #14 is the thin wire TO the ECU pin #18, and this is the only communication the ignition system has with the fuel ECU.

The memory is getting flashes at times here, dont laugh, it happens, BUT, inside that amp is that rubber BLOB, and inside that rubber blob are 2 resistors.

Now the fuzzy hits.

One is for the tacho, the other I "think" is the one for this thin wire, so if I am wrong, so be it, but I do remember that if one of those resistors fails the tacho stops, big deal, if the other fails the engine stops. I wonder?????.

These resistors are NOT shown on any diagram I have ever seen.

 

Good stuff Grant. One resistor is for tach (engine speed) and the other is telling (pulsing) the ECU how fast the engine is going? Without it, no fuel delivery?

Therefore, it makes sense that this a RF cable hence the shielding and ground on one end to attempt to block interference? Interesting. This car can be shut off by sending a interfering radio signal? I know, I kind of went too far on that one. LOL

In the grand scheme of things, the ECU is there to control fuel delivery not the ignition so it needs several inputs to make that happen. Temp, speed, power, etc?

Good stuff and great research Grant.

 

Thanks Abe.

The ECU is FUEL ONLY, and requires that signal via the coax purely to acknowledge that ignition pulse is present.

NO pulse, NO signal, NO fuel activity past priming the fuel system.

Soooo a stalled engine has NO pulse, so NO activity, sweet.

Sadly the wire gets fried behind the engine, and changing #6 spark plug on each side usually has it pushed and shoved in all directions, and old age takes care of the rest.

The coax was also to shield interference from the spark plug leads, or so I am led to believe.

Mine has the ign amp out the front, near where the front coil used to live, and I ran the leads up the RH inner guard, NO coax cable at all. I spliced into the factory coax at the bulkhead connector behind the RHF wheel panel. That was 10+ years ago, and still sweet.

 

Thanks to all of you, and all of your great advice. Unfortunately, I've done all I can do and I'm exactly where I started. So tomorow she goes to the local Jaguar dealer for some proper repair. They'll get her running again. I've learned alot from this forum and it's good to know there's still a few good people out there willing to take time out of their lives to help someone in need. Thanks a million. And I'll report back with the dealers findings.
Kevin

 

Well good luck with the dealer. They may find that you forgot to turn the key - LOL just kidding.

My jag starts but runs bad and shuts off when warmed up. It also misses real bad on the right bank (A). I changed the plugs and swapped the coils to no avail.

When I got this car, an inexperienced person broke switches, wires and vacuum hoses under the hood. I had to go through each system to reconnect and repair it. On top of all of that, the car was vandalized in the interior where they broke up the window and top switches and pulled wires out of the dash. I had to collect all the parts and repair. The last to do is the upholstery and repair the seats.

I will do body work and paint next spring

Most would give up on a car like this but not me. I just like British cars and the abuse they can give to a mechanics nervous system LOL

It needs a complete exhaust system now as I figured out that the cats are fried. I want to just put two after cats on each side and pipe to two glass packs or Turbo mufflers. I need some throaty sound. This is going to be my weekend car.

Well looking forward to hearing about their findings.

Abe

 

Well, after 3 days at the Jag dealer, my car is back up and running. Grant, You were spot on. No power to pin 18 at the ECU. I also had them replace and re-run all of the coil and amp wires as well as the CTS wiring. They mentioned pin 1 getting a weak reading. They fixed that wire as well. Thanks again to everyone.
Kevin

 

Glad to hear its fixed.

 

SWEET.

Next round is on Kevin.

You are lucky the dealer even wanted to look t it. Down here, anything more than 5 years out of warranty is a no no.

 

The same thing happened to me on my xj-6. Driving along in traffic at about 35 mph and the motor just shut off. no warning at all.. just stopped. Trailered it home to my shop. After trying all of the things you guys have mentioned I tried tracing the white ignition wire from the ignition switch to the coil. That was it. I never found the actual short in the wire so I just by-passed it through the firewall directly to the coil. That new GM module started to smoke my coil. I went back to the original module and got a much heavier ignition coil. I eliminated the ballast too. Now.. these ignitions are not the same but the symptoms seem similar. My XJ-6 has never run better or smoother since. I have three 12 cyl Jags and have never had an issue with the ignition system (yet). Hope this helps. Kev