Ok, after 6 more hours in the workshop and almost loosing faith in my brain i found the problem

I was measuring and suddenly i had a connection to earth from both ignition + connectors - even between battery + and earth, even though the ignition key was not connected i measured 3 Ohm. the next moment it was 300 Ohm, then no connection.

I tracked it down to this connector in the firewall, behind the battery:


when i unplug the first connector (with the ignition plus) the connection to earth is gone. I have a clean connection between the connetor on the cables to the coil and a clean connection from the connector in the firewall to the ignition key. When i plug it in onl a few mm everything is fine but as soon as i plug it all in i get a unstable connection and a connection to earth.

Both male and female part look decent.




Well, what now? change the connector on the cable?

 

I believe looks can be deceiving. If it were me, I would curl up a piece of 400 grit paper (grit on the outside) and work it in and out of each of the female connectors, then pinch each connector a bit. There should be a slit in each female connector that needs squeezing? Then do the same treatment to the male studs, this time with the grit on the inside of the curl. Then a bit of dielectric grease on the female connectors, then push the two connectors fully in. IF that doesn't cure the problem, then it's the wires to the actual connectors - either on the plug or the jack. The plugs obviously being the easier to cure. The jacks are mounted in the firewall and harder to get to the backside. Hope this helps.

Bill

 

That firewall block has a male connector on the other side. The problem could well be that side, as when plugged in the problem appears. I would take a look there before doing anything further.

 

yes unfortunly the plug is merged to the cables so its not easy to get/change. i have a old wireing harness that came with the car, maybe there is a better plug on it. Then i could change it with a short peace of he cables and then crimp them.

 

I would solder then heat shrink rather than crimp. That's just me though.

 

So today i startet it again and a little teaser: nothing changed.

What did i do since the last startup:
- changed to new: Distributor Cap, Distributor Finger, HT-Leads, Coil
- cleaned the Battery + Stud on the firewall
- checked and cleaned the Ignition + connection. The connector in the blug seamed a bit too big, i closed it a bit, cleaned it with sandpaper and now i have a stable, clean connection with 0.0 Ohm to the ignition switch
- checked and cleaned the ignition switch itself
- new battery
- closed a minor fuel leak that occured at the last start up in the new fuel lines
- added the missing fuel tank selection valve and replaced one return valve because it was broken
- cleaned the connector to the injection resistor pack

I started it today and it again had a really hard time to come alive. I tried priming the fuel rail several times, pressing the paddle though befor start - still needed 7 trys till it startet.
i let it idle for about 30min.
here is in detail what happened:
- about 30sec. after startup the coolent filler cap in the middle overflow pretty bad, soaking the whole engine bay (that i spent weeks cleaning) in coolant - yay. after that no more coolent leaked - i assume i filled it up too much, since it was standing for weeks and i always refilled it when the level setteled? I have to check the level as soon as it is cooled down now.
- it idled at about 1200rpm for 1min, then went up to 1400rpm for maybe 20seconds and then settled at about 1300rpm
- it idles smooth (for my point of view, i have not much experience with V12 engines) and responses well. No misses or wrong fireing.
- temperature got up after about 3-5minutes and reached 70°C according to the instruments. Sometimes there was a short (1sec) jump to 80-90°C that i cant explain. the electric fan was running after a few minutes after startup
- idle went down with rising temperature and settled at 1000-1100rpm at 70°C
- the temperature did not rise further in the 30min and the idle did not change further. So i assume the AAV was not fully closed yet.
- there was no further coolant leak
- when i open the throttle a very small amount it seems to run a bit rough - and with a bit rough i mean that you can barely feel that the engine is even running, wich you cant in idle and at higher rpm

So, now i am thinking what to try next.
- The last point got me thinking - i adjusted the throttle linkage - do i have to set some zero point at the throttle position sensor or some switch? Maybe there is something not correctly adjustet and hence the hard start?
- why does it not heat up further? is that normal when its just ideling? Cant take it for a spin atm because im still waiting for the registration.
- anything i can look into further?

or should i just enjoy it and follow Grants advice and declare it female

 

The car should start immediately from cold if all is well. The problem is there and must be found, the V12 HE is not a temperamental engine.

Start with the basics: If it will not start, have you verified that there is a spark when cranking from cold?

Once this is known let us know.

 

Ok, what i did today:

I measured the coil voltage while cranking (coil+ to battery -) and it drops from 12.6V with ignition on to 9.0V when cranking - oof, thats not good.
So next i measured the battery voltage itself. It also dropps pretty bad to 9.6V while cranking.
I checked the spark as well - it has a spark but not consistant and pretty weak. i made a video:

Then i measured the Voltage between Battery + and Coil +. Thats 0.1V with ignition on and 0.6V while cranking. also not that good.
That 0.6V drop is even there when the coil is disconnected, so it must come from somewhere else while cranking. So i disconnected the ignition + from the starter relais and the 0.6V drop was gone.
So the first step will be, i replace the starter relais.

BUT this will not solve the massive voltage drop at the battery. The only thing i can think of that can cause this is the starter motor itself, since the battery is brand new and fully charged. What do you guys think?
Does that mean i need a new starter motor?

 

Have you replaced the igntion amplifier?
Have you put a relay into the igntion circuit to deliver a good 12v to the coil?

If the starter turns over the engine properly, it is fine.

 

Check the earth strap fiasco at the LH engine mount. WELL documented over many years that these 2 straps fail to earth the system as desgned, so it looks for other earth paths, gear cable, throttle cable, etc etc, NOT good.

That voltage drop is consistent with the electrical section of the Ign switch needing a service. Then that relay in that White wire to tge coil, MUST DO THAT.

Going around the +ve and -ve connections in the engine bay, and there are MANY, and ensuring they are dismantled and cleaned correctly is paramount to good starting, and trouble shooting.

Starter motor issues, RARE in any country, often blamed, but rarely the issue.

Starter relay, maybe. Check the integrity of the White/Red wire push on terminal at the, often NOT tight. Squeeze it slightly to tighten the grip.

That battery dropping like that is either a suspect battery, or, as mentioned, very bad earths in the system, probably both.

 

No i did not replace the inition amplifier yet.

I put a hot wire between battery+ and Coil+ while cranking, maybe a tiny bit better starting but far from good. Stoll only 9V while cranking since the whole battery goes down to 9V.
The Battery goes down to 9V even with disconnected coil and amplifier so i did not suspect that unless its normal that the voltage drops to 9V while cranking.

I had a starter on my mini that did turn but burned down a 300A relais and amost cooked a 50mm² wire.

I will check all earth connections next. Although i cant imagine how a bad earth can cause a voltage drop at the battery (measured between the two poles)...usually thats only possible when you take a HUGE current.
So i also will check the main wire to the starter for possible ground contact.

I would rule out the battery since it was the same with the old battery what was in good condition and the brand new battery

 

So i spent enother three hours in the workshop and did my earth- job. I found 8 earth points in the engine bay, i opend every single one cleaned them with a wire brush on a dremel, put some contact spray on it and put i back together.

I also checked and cleaned the positive post on the firewall on the left hand side since i already did the one on the right.

Then i went down under and checked the mass stripe between the housing of the gearbox and the chassis. I didnt look bad. I had a new one laying around so i replaced it anyway. Also cleaned the metal on the chassis and on the gearbox with some sandpaper.

ok maybe a bit too big but hey its a earth, that cant be too big

Ok done that, tried to start....nothing changed.

Did i miss an important masspoint? i looked at the ones you can see inside but they look better than new. Are there more under the car?

EDIT: You wrote about a two strap ground at the left engine mount. i couldnt find one there - anyone has a picture or a drawing where this one should be?

What i would like to try now:
Get a clip on amperemeter and measure the current while cranking.
Maybe connect a second battery with jumper cables to see if that holds up the voltage better.
But first i will take it for a longer drive ... maybe its just dirty or wet plugs from all the cranking and ideling

as i wrote...only a high load on the battery can cause a voltage drop directly on the battery

 

I have another question according the cooling system. I filled it according to the workshop manual.
I opend both caps, filled in the middle. It says fill until the side tank is full, but it didnt really fill with it.
After a day or so it went up until the tank body was full, so i declared it full, closed the cap and filled in the middle to the right level.

Now when i started the car i had this massive overflow from the middle filler cap. It was maybe 30 seconds after start, then stopped and didnt leak further even when heating up.
When it cooled down i checked the levels. The side tank is half full, maybe a bit more and the middle filler is at the correct level.

When i got the car, befor renewing the coolant it was at exact the same level. Now i assumed that i just overfilled it and it spilled out what was too much. But further reading got me nervous that maybe something is blocked there? I read that the side tank should be filled till it runs out at the top? Wouldnt it overflow then everytime you open it after its all filled?
I will Check the bleeding lines too - maybe there was a huge air bubble in the radiator that rushed through and caused the overflow? Or is the level i am seeing normal and i should not worry about?

EDIT: and another Question: Is the rotational orientation of the jiggle pins in the thermostat important? There was no noteable pattern at the old ones, i fittet them with the jiggle pins at the top.

 

Check the follwing for blockages

• cross pipe
• all the radtop air piurge pipes, banjos and flexibles
• the pipe from the crosspipe to the header tank on the wing (the "question mark") pipe
• the overflow pipe to the atmospheric tank
• the heder tank itself and its various spigots
• when you filled the radiator, did you undo the bleed plig on the top LHS of the rad? Also undo this when topping up.

The jiggle pins at the top is correct.
If all Ok with the above, the maybe you have a water pump problem or some blockage inn that assembly.

 

Ok, i will check these points.
In the instructions you should fill the header tank from the middle filler till it overflows - but then i have read on several sites that is usually just 1/2 to 2/3 full. What would be the correct filling level after operation?

EDIT: forget it, i understand now - The header tank is filled up all the way, then expands into the athmospheric tank. after the first expansion it is half empty.

 

So i checked all the mentioned lines and they are all free. So i undid the bleed screw of the radiator, put the whole car slightly uphill and filled it all up again - filled in another 2 liter, definatly more than what was pressed out. there was a lot of air left in the radiator.
Started it up, took it for a spin and nothing spilled So i think i can cross this topic off my list.

Also just to check i put in a relais that connects the coil directly to battery + when ignition is on. Without any change.

Points i have to check now:
- Earth straps near engine mount as mentioned...i cant find them and dont know where they should be.
- measuring the battery current while cranking. The starter has somewhere near 1.8kW, that means there should be somewhere between 150 and 200 amps depending on the efficiency and the other loads
- changing the starter relais

 

Have you changed BOTH coils and ensured they are corrctly connected in parallel by the two wires that link them (+ to+ and - to -)?
Have you checked the connectors on the coils (the copper breaks inside the insulation) fitting new connectors is always a good idea.
Check the connector to the 'dreaded white wire' the one leading from the Lucas amp to the loom
Check the connector in the V from the trigger on the dizzy bottom that exits the dizzy bottom in the front of the dizzy and leads to the amplifier.
Have you replaced the cooant temp sesnor on B bank thermostat housing? Also check that the air temp and engine temp loom plugs are not on their wrong sensors, as they both are the same. Some looms are marked "air" and 'engine", if not check the wire colours agree with the wiring diagram.

If all this is Ok, I say buy a new amplifier from Manners, which I suspect is the problem anyway..

 

I have a new high performance coil (single coil) instead of the two ones. Connectors are all new, even the one in the V.
The water temp sensor is new. I will check the wire colours.

Would a faulty amplifyer affect the running engine as well? maybe i check the connectorsin the amplifyer first and then maybe rebuild it....new amplifyers are really expensive here in austria - and ordering somewhere else we have high costums.

 

Many different problems associated with bad module in ignition amplifier, other parts inside amplifier, usually short out and you get no start or run. Some guidance on repairing amplifier below.

inhttps://www.jaguarforums.com/forum/attachments/xj6-xj12-series-i-ii-iii-16/217204d1541893758-jaguar-xj6-s3-ignition-system-repairs-jaguar-lucas-cei-amplifier-repair-xj6.pdf
Rgds
David

 

Thank you for the pdf i can get hold of a PetronixD72000 to a reasonable price. So if the start relais and the starter motor is fine i will try that.

What i dont fully understand is, is there a difference for V12 and 6? is the PetronixD72000 fine for the V12?