I would forget an aftermarket ignition system. The HE ignition is extremely robust and quite efficient. Your problem is not the system, but a part of it that is malfunctioning.

Something else to check: A failing resistor pack can cause your problem too. See this link:
https://www.jaguarforums.com/forum/x...sistor-134745/

 

i already checked andcleaned the connector of the resistor pack. Are there "should be" resistance values that i can check?

here is a picture of the plugs i took out after i got the car. the last drive was about 30min.
To me they look good - would not suspect it to run too lean. But maybe i am wrong what do you guys think?

 

Plugs look fine. Have you checked that fuel is being injected at the cold start. If so and if it is, it is spark. Can you borrow an amplifier from someone to try, if buyng a new one is impossible? If it was me, the amp would be the first thing I would try.
This might help
Here is one in Germany, only the price of a couple of tanks of fuel!
https://www.jaguar-shop.com/Ignition-amplifier-53l-V12

 

i just changed the start relais and all its connectors. Remember, i had a 0.6V drop between battery and Coil with the old one. Now i have only 0.2V drop.

Battery still drops to 9.4-9.5V while cranking but the 0.4V more on the coil seem to help very much. It didnt start like when its slightly warm (does take maybe 1/4 engine turn and it runs) but after a few turns it starts now.

I assume it really is the voltage while cranking. The starter pulls 300-350amps. that a lot in my eyes - i assume it works but is not in good condition. maybe a short somewhere in the windings or bad coals.

 

It is certainly possible the starter is going home and drawing huge current. Not that hard to change it, but consult here if you decide to, as there is one very tricky bolt that can be ruined and become un-undoable if you use the wrong spanner! A modern gear redcution type is also a good idea as they drw far less current.

 

Yeah since its not a daily driver and if it keeps starting like this i will leave it in for now. If it gets worse i have to change it.

 

The 4 pin Pertronix D72000 module is not a new system, it is a direct replacement for OEM "AC Delco D1906 Ignition Control Module" 6 cyl, or 12 cyl. (if 4 pin module is required)
My view is the (9 volt during start, is the real problem) don't know what the cause is, but would continue to chase that. Just to confirm, you could jump a second battery to first to see if starting becomes more robust with two batteries overcoming the large draw you are experiencing.
Rgds
David

 

i did a longer drive and on tje next day it startet very well. I assume it really was the start relais. Anyway i will test if its even better with a second battery, but for now i have to deal with another problem.
I finally came to a gas station and filled both tanks up to half full (thanks god not toally full).
At home after an hour i noticed the extreme fuel smell and then the next hour a puddle of fuel under the right hand tank. Opened the rear light and saw it almost constantly dripping out at the fuel level sensor.
The Sensor as well as the sealing are new :/. Maxbe i just didnt close it tight enough....other than that i dont know how to close this leak.

 

The car is starting really reliable now even when cold. a second battery does not change much.
I took it for a two hour drive now and noticed it is not getting hot enough. Anyone has a idea what can cause this? It goes up to 70°C pretty quick (maybe 2-3min) and stays there. Sometimes goes up to 80, then again back to 70 - the changes are pretty quick. But it never goes over 80°C. I had a faulty instrument or sensor in mind but i measured with a infrared thermometer at the thermostat housings and they are both at 70°C. Thermostats are new. It was about 14°C ambient temperature.
In the V is measured about 100°C, Cooler hoses are also at 65-70°C
The idle starts at 1400rpm and goes down to 1000rpm and stays there - i assume that the AAV closes up to 70°C and not further, hence the higher idle.

I know people usually complain about hot running jags but at this point i have no idea what can cause this? Maybe a leaking filler cap so it cant build up enough pressure? There is no coolant spillage whatsoever.

 

A short answer might be that even thou the thermostats are new doesn't mean they work according to spec. Maybe pull them out and go with heating water on the stove and suspend each thermostat, noting where they open and close?

Bill

 

i drained the system again and refilled it according to grants instructions cause i felt some air in one hose. i got a better connection between the two levels in the filler caps and needed about half a liter more coolant.
When started it leaked out of the cap on the wing tank slowly. When i pressed on the cap it stopped and the hose to the athmospheric tank got hot. I assume this cap is just old and leaking, i will replace it.

Anyhow,i also noticed the fuel pump is leaking. And someone familiar with V12 told me that the engine is running far from good. You can feel it ideling when sitting inside and it sounds too rough when accelerating. Guess its back to the scratch.
I listened to the injectors with a stethoskope and they all click and sound exactly the same. Since i cleand and tested them outside i cross them off the list.

Maybe it really is ignition...the amlifyer?
Or - in best cause - the leaking fuel pump didnt provide enough pressure and it was the problem all along.

 

Ok, here are some good news: I changed the fuel pump and the fuel filter and it startet really well from cold. even better than it startet hot befor! Maybe it was the fuel pump all along and the start relay was just i minor factor that made it worse.

When the wether gets better i will take it for a drive and see if it runs better and has more power.

For the cooling topic: I did some reading on infrared thermometers and learned that it is more accurate to ask a glass ball about the temperature of aluminium than measuring it with a IR thermometer. Depending on the oxidation, roughness and how clean it is, results can vary by 300% So i guess i dont rely on the thermometer.
Unfortunly i dont know another way to accuratly measure the real temperature. I will change the coolant temp sensor and check the wireing.
And i will replace the two filler caps since one was leaking.

 

Use one of these with the probes taped to what you want to measure. You can get long probes and run them into the cabin to see temps in real time:
https://www.ebay.co.uk/itm/134110932...Bk9SR_q-hpezYw
Dead accurate and very useful.

 

So i took it for a spin. Today it didnt start as well as last time. we are back to a "okay" start when cold. Meaning that i crank for 3-4 sec befor it starts. Maybe i celebrated a bit too early. Although the engine sounds better when accelerating at low rpm, i still think it has a lack of power (my feeling can be wrong, never drove anothet xj12) and runs rough on idle (still can feel the car slightly shaking when sitting inside). Also it does not have a constant flow on the exhaust, you can feel interuptions in the flow on both exhausts.
I guess i will have to change the ignition amplifyer....maybe i have a chance to get one to cross swap first to see if it makes it better befor i buy one.

Maybe i also have another look for vacuum leaks, although i tested all connections to the engine for leaks and the only open connection is the AAV and the engine breather.

here is a short video of the engine ideling at 1100rpm after 20min drive and 70°C coolant temp:

Alsoi glued a thermometer to the pipe next to the temperture sensor and it reads the same 70° as the instrument and the IR Thermometer....so propably it does read correct. I guess i will pull out the thermostats next, but since the temperture was the same with the old thermostats i dont think thats the problem. I mean whats the chance of getting 4 simular broken thermostats?

 

i drained to coolant today and will pull out the thermostats this weekend. Will test it along with the old thermostats.

I have also looked for vacuum leaks in idle. You guys have to help me understand two things:

First the engine breather:
The engine breather is connected to the left air filter housing and open to the air filter. In the connection is also placed the PCV. That means the PCV is also open to the air filter....how should the PCV build a vacuum in he engine breather if it is open to the air filter? the small flow wouldnt affect anything if there is this huge hole to the air filter.
Also: shouldnt the PCV close completly in idle / max vacuum? I tried to somehow test it with a large vacuum pump and it didnt close/move at all. The piston is free, it just seems that the spring is too strong that it closes.

The second thing i am wondering:
The fuel breather system should somewhere be connected to the vacuum. inbetween there shouldbe the charcoal cannister. Heres the thing: i cant find a connection to the vacuum nor a charcoal cannister at my car. In the fender there is only the vacuum reservour for the brake servo on the right and the athmospheric coolant tank on the left.

 

update:
Today on the menue: thermostat soup


All four thermostats open at 82°C as rated and fully close again at 78°C
I noticed that the old ones have other jiggle pins than the new ones:



This ball in the new ones is veeery tight and i assume it makes bleeding harder than it is anyway. So i drilled it out and put the jiggle pins from the old thermostats in the new ones.

other updates:
It appears my car does not have a charcoal canister, there is no connection between the fuel tanks and the engine except the fuel line and return line.

I also noticed that when i unplug the vacuum line that controls the vacuum advance of the ignition and put a vacuum pump on it, it does not build vacuum.
I have the "Emission B" setup as in following link:
https://www.jagweb.com/aj6eng/vacuum.php
I have connected the pump to the connector on the manifold head and to the one above the throttle body. both do not build a vacuum and both do not produce a vacuum at the ignition advance.
I have to investigate that further, maybe i have a leak there and/or no advance in idle...hence the rough idle

 

The extended length of the thermostats in the fully open position is at least as important as the opening temperature. The bottom disc must fully close its port when the thermostat is fully open. They must open to at LEAST 41mm, measured from the big disc to the small. More is better. If they don't open that far, don't use them. They will never allow the engine to cool properly.

It's very common for the vacuum advance diaphragms to fail. However, some, but not all, versions have a controlled diaphragm leak for in-line vacuum regulators to work properly. If you apply a constant vacuum to them, they will move and change the advance, but don't hold a perfect vacuum. So different diaphragms for different versions of the distributors, so you have to get the correct one for your engine and emission system.

The pdf in the first post of this XJS sticky provides good info on the V12 cooling system. At the botton of it is a writeup on the thermostats.
https://www.jaguarforums.com/forum/x...aining-219536/

 

Thanks for the length i will re-check that. the new ones open a bit further than the old ones. but i will measure it just to be sure.

the vacuum cell was broken i already replaced that. i unpligged all connecrions, blocked them and apllied vacuum and it didnt hold. also no vacuum appeared at the advance connector - somethings fishy here

 

Measure quickly. They start to close very quickly once taken out of the water.

 

They do open far enough after a while in boiling water - bjt appearently they should open further above 100°C. A guy who does a lot with jags told me - cant really try that.
He also told me that there are usually 88° Thermostats in the HE - i had 82. So i got 88° Thermostats, testet them befor this time and put them in.

Since i had it partly disasemblied again in the workshop i made a list to cross off some points.
On this list is beside checking of fuel pressure is also a leak down test of the cylinders.
I know this should be done on a hot engine but thats not that easy on the V12 since you need at least half an hour of work to get to all spark plugs. So i did it on the cold engine - just to compare the cylinders not to get a accurate measure. And now i have bad news.

I did not do all cylinders yet. But i have 15% loss at 1A. What is pretty good for a cold engine. Then i have 25% at 6B.....that not horrible but far from good. I would blame the cold engine if i couldn't hear a hissing in the plug hole of 5B. Bummer!
I am not 100% sure its the head gasket but it really look like it. The plugs all look good.
5A also has 23% loss and a slightly less (but noticeable) hissing in 6A. Here i also noticed a hissing in the inlet manifold.

So here i am thinking about what to do. There are no other signs of a failed head gasket. no smoke, no water in oil, no oil or water consumption, no pressure in the coolant system. But it can be blown right between 5 and 6...at both banks exactly the same? what the chances?
Or maybe its the inlet valves and it blows in the next cylinder via the inlet manifold?
What would you guys do in that situation? Taking the head off just to be sure? I would do that at a mini where a head gasket is a 30min job, but not at a Jag V12 . Currently i am thinking about running a system cleaner through the system to clean possibly dirty valves and see if the idle problem has other causes (vacuum advance for example)