Hi Guys!

Santa doesn't like xjs: He took me a new issue for my cat...

Few days ago, suddenly, the engine has started to misfire on the A bank and the catalytic convertor of this bank started getting so reeeeeed; quickly I've turned off the engine.

In the next days I've managed to determine the misfiring cylinders: 2A, 4A e 5A... the spark plugs of these cylinders were wet of fuel...

Cleaning all the spark plugs I've then managed to start the engine again but the A bank misfired merrily as before!

I've tried to use a stethoscope listening to each injector of the A bank while the engine was still running and every injector was working.

Now, while I'm ruminating on this issue, the cat show another “little” prolem, the engine doesn't start at all: no spark!

What can I check now?

Thanks!

Tommaso

 

Hi Tommaso

You are very lucky that you couldn't get her started, or your Car may have just turned into a Fireball by now!

As what you have experienced has got all the Hallmarks of a Marelli Fire.

The Marelli distributor is like having Two 6 cylinder Engines and when one side stops working as it has done, then the other side pumps raw fuel

into the Exhaust Pipe which can cause your Car to Catch Fire and then burn to the ground.

Which was why the Cat on 'A' Bank was glowing Red.

So don't attempt to Start her, as you may not be quite so lucky next time.

It looks like you are going to need a New distributor Cap and Rotor.

If you take the Marelli distro Cap off you should be able to see where it was arching and burned through.

Marelli Fire Syndrome can be caused by bad Maintenance with regard to the Spark Plugs, especially the ones under the Aircon, that sometimes

don't get changed when doing a Service.

So best to replace ALL the Spark Plugs.

This is the definitive fix to try and make sure that this doesn't happen again.

https://www.jaguarforums.com/forum/x...photos-135024/

 

Hi Orangeblossom,

thanks for the reply!!!

The problem is that I have Lucas type distributor...

Sorry for my misunderstending!!!

 

In that case it is almost certain from the symptoms you describe that the three injectors are staying open as a result of a short to earth in the injector loom. It will still put you in danger of a serious fire though as you have catalysts. A 1989 V12 with Lucas ignition is quite unusual though, do you have the Lucas amp on the B bank intake manifold?
IF a Lucas, my advice is not to drive the car until you have renewed the injector loom, and the oil as it will have petrol in it. If Marelli, as OB said, but as well as plugs and the dizzy rotor fix, new HT leads and for safety, amplifier modules and loom is a pretty good idea too.
Greg

 

Injectors are grouped 1,3,5 and 2,4,6 - still could be the harness.

To check the injector loom.

Turn the key to on (DO NOT START the car)
Measure the voltage on each pin of the injector plug (injector still plugged in) on 2A 4A and 5A you should read 12volts on BOTH pins if one side has 12V and the other side 0volts the injector loom is shorted to ground on the ECU side.

 

Hi!

Thanks Greg! Yes... I've the Lucas amp in the intake manifold... Maybe it's the amp itself the problem 'cause now I've no spark in any cylinder, but I've spark in the HT lead to distributor...

Thanks Warrjon, I've checked the injectors as You said and the voltage is the same for all: 12V on both pins, I've dismantled the injector rack too and the injectors do not leak with the car key in on... so I think they're ok...

I start to think my problem is in the ignition amp or in the distributor... Can I use multimeter ti check these?

Thanks,
Tommaso

P.s. Happy New (incoming here in Italy) year!!!

 

If injectors are OK then I would next look at Ignition leads. The ends are crimped on and have a tendency to come loose pull on the ends if its loose it will come off.

I do not think it will be ignition amp, if this was at fault then it would cause issues will ALL cylinders.

Could be terminals in the distributor. Pull the cap and check the terminals make sure none are scorched.

 

If you have spark at the distributor end of the coil lead then everything up to that point, including the amplifier, is working.

If you are not getting spark at the end of any leads then it's almost certainly not 12 bad leads. That leaves the distributor cap and the rotor. Your problem is with one or the other.

 

To summarise all the good advice above, if the parts are old in the dizzy cap/rotor/HT lead/plug chain, quite honestly the best thing is to change the lot, as you are probably close to a fail all through it.
The only other thing is if you have three injectors leaking, this will prevent a cylinder firing even with good ignition components. Can you definitely hear the offending cylinders' injectors clicking? Anyway, if the ignition stuff renewal does not do it, then you are looking at either (a) an injector loom problem or (b) cleaning the injectors. Orangeblossom did his at home, no trouble. Just a bit of a pain getting them back in without help. Also has the advantage of renewing the rubber rail to injector pipes, that will also need it anyway.
FWIW, my money is on a loom problem if the ignition renewal does not fix it!
Greg

 

Greg

Re: Tommaso's problem:

Could it be a dirty Plug and Socket on the Resistor Pack down by the Headlamp Nacelle?

When you put me wise about that, my injector problems simply disappeared.



Resistor Pack on a 1990 XJS V12 this ones on a Marelli but a Lucas Car has a similar thing.
A dirty plug and socket can cause Injector Havoc.




The Resistor Pack Plug also needs to be Clean

All Credit goes to 'Greg' for this Brilliant Fix, which simply cured all my Injector Problems, although I also had to Clean the Injectors as Six of them were Stuck.

Cleaning the Injectors was dead easy to do at home, with no Special Tools required and now She's running perfect.

 

That is a hell of a good point OB. OP should surely do that.
Greg

 

Just to add to the "to do list".

You say the coil lead has spark TO the cap, yes?

The sparkers are NOT sparking as they should, yes?

Remove the distributor cap, easy, and turn it over and look at the centre post carbon contact brush. Is it still there???.
They have a habit of going AWOL. Some fall out when you are busy in there doing important stuff, some burn away.
Mine burnt away, and it had some really strange mis-fires, that had a for sale sign on the windscreen, and some 5 weeks later I found it, and NEVER forgot what I found.

 

Hi guys!

Quick update: cleaned distributor contacts and spark plugs wires and now I've regular spark in the plugs... but the car doesn't start yet!

Checked again the injectors loom and now I have 12V IN ONE PIN AND 0V IN THE OTHER PIN of the plug ... IN ALL INJECTORS!!!

Strange: when checked the loom last week as Warrjon said there was 12V on both pins...

Cleaned resistor pack plug and socket as Orabgeblossom said... but nothing changed.

My ECU is shorted? How can I check where is the short?

Thanks!
Tommaso

 

Most likely the injector harness will be the culprit. Disconnect the injector harness plug on the LHS of the engine near where the wiper fluid filler is and check continuity to ground, I would suspect the issue is in the engine bay. If this measures open circuit (no continuity) tug on the injector harness in various places, give it a good rattle.

If after a while you can not get it to fail then check continuity from the plug to ECU to ground.

 

My internet is still blasting along at 11kb/s, so adding stuff is impossible.

Locate that shielded wire from the ignition amp, and unplug it at the amp, then unplug the ECU. Locate Pin #18 in that plug. Do a continuity test of that shielded wire, front to back. Use the imagination for a loooooooong test lead. The very fine signal wire inside that shielded unit breaks too easily, and without a pulse from the ignition, the injectors will not fire.

BUT

That voltage test is looking horribly like a major injector loom failure, and you are not alone, it is common now.

 

Good evening!

Following Your good advices (here and in other posts) I've worked to found something wrong in the harness but... Nothing!

Here results framework:

Continuity between amp shielded wire to PIN 18 ECU plug: checked!

Continuity between PINS 1,16,17,34,35 ECU plug to ground: checked!

Continuity between PINS 31,32 ECU plug to OW wire in big injectors plug LHS engine bay: checked, as well as PINS 13,14 to OU wire, PINS 27,28 to OG wire and PINS 8,9 to OS wire.

No continuity between injectors plug wires to ground!

Continuity between PIN 11 ECU plug to KS wire in power resistor plug: checked, as well as PIN 29 to KG wire, PIN 12 to KU wire and PIN 30 to KW wire.

Continuity between PIN 5 ECU plug to coolant temp sensor OU wire and PIN 19 to YB wire of the same sensor: checked (car doesn't start neither bridging pins in the sensor plug).

When I turn the key on there're 12v in the four injectors plug KB wires but nothing in the OW, OU, OG, OS wires (as well as there're 0v in KS, KG, KU, KW wires of power resistor plug).

Checked TPS too: the volts, opening throttle, rise smooth between red and yellow wire until 5v; the starting point is between 0.3 and 0.4v (analog mutimeter).

At this point my hands can measure ohms without the meter, as well as volts... with a little pain!

So where can I point my attention to solve the problem?

Thanks!!!

Tommaso

 

The next thing to check is the injectors.

You might have sticking injectors, pull the injector rail and injectors and clean them with carburetor cleaner, there are loads of YouTube videos on how to do this.

 

Quick update!

Now the cat seems to be ok: she runs fast and smooth!

I cannot really know the answer: maybe all the harness, plugs and injectors clean up job... Maybe she just seems to be in good mood...

By the way... Thanks all for the support!!!

Tommaso

 

Well done, whatever you did.

I reckon that car sensed your FEAR, and that put it in commond. Once you settled that point the car conceded.

Probably a combination of all the things, and that can be frustrating at times.

I would be running a serious dose of Injector Cleaner in the fuel on a regular basis. Brands mean squat, I usually grab whatever is on sale when I need it.

My HE got a bottle of brew once a month, but it was the Daily Driver and did mega miles.