I did a search, but came across series 3 info only. This is my first series 2 V12 car, and it IS different !
1978 Jaguar XJ12L ( Canadian edition )
Known history:
Not licensed since 1989 ( MAN, this car must have gave somebody trouble ! )
Sat for a number of years, before I got it last month ( October, 2015 )
I managed to get the engine "almost running", and backed the car off my trailer.
Known problems that have been remedied:
Stale, old fuel.
No fuel pump
Engine ran from right tank, but system circulated fuel to left tank only. Switch in wheel well defective, as well as blockage into tank.
A few wire connections at coil / amplifier.


Current / recurring symptoms:


Difficult to start... warm or cold.
Mis-fire... that tends to clear up when the accelerator pedal is "pumped" a bit. ( engine seemed incredibly lean )
Engine will typically not keep a sustained speed... part throttle, or under acceleration. Again, seems to require "pumping" of the accelerator pedal.
Intermittent back-firing... both, into intake manifolds ( left in particular ), and out exhaust.
Extremely weak / misfiring idle... yet, if the accelerator pedal is "finessed" stragegically, the engine will for a moment, rev incredibly smoothly.
The power IS there, when it catches on occasion.


Last night, I advanced the timing.
strange... ?
Now, it seems to almost retain a cruise RPM.... but now goes excessively rich everywhere else.


I have never been able to locate any service information on the series 2 injected V12's... including tune up specs, timing settings, and procedure, ect.


Can someone help me with this ?

 

First things to check are the coolant temp sensor and the intake air temp sensor. The air intake temp sensor is on the left hand air box.

2nd thing to check is proper injector funtion. Those injectors are notorious for getting stuck. Apply 12v to each injector and listen for an audible click.

 

Well I'll be !... that is EXACTLY what I was thinking !... Those temp sensors.
I'll check those injectors as you mentioned too.


Thank YOU for replying.
BTW, I should mention, this car has only 107,000 KM ( 65,000 miles ) on it !

 

Also,

The injector "pulse" is supplied by a trigger board under the distributor cap. Early units were a 3 wire unit, very unreliable.They have reed switches imbedded in that board.

Replacement boards are a 4 wire unit. These have hall effect sensors imbedded in that board. The 4th wire being attached to a 12V ign switched supply. Very reliable.

The rotor button has a magnet in its heel to activate these switches, and magnets do die, fact.

The "pumping" of the throttle actually activates the injectors as designed. That is the enrichment feature built in. Test this by turning ON the ignition, engine OFF, and open the throttle. You should hear the injectors click as that switch passes over its segments, 9 I think? These switches get "dirty" and the adjustment is a mongrel on a good day. I have that procedure somewhere, so if it is needed, ask, I dont bite anymore.

The plug that plugs into that switch is also notorious to unplugging itself inside that large rubber boot, so check it carefully. It is not a good tight fit, never was.

Gummed up injectors after that time will be a given.

The 2 FPR's will need checking and the pressures set, just again due to time, and the unknown.

The list goes on, but that will occupy you for an hour or two.

 

That's some info right there, Grant... thank you !


In order:


That "trigger board" ?
I DID have that off... and since, the engine DOES seem to get rich at times.
Now, it being just a trigger... wouldn't it be a go or no go scenario ?


Yes, I had confirmed the effect of the pumping of the throttle. Works fine.


The fuel pressure regulators... yes, I AM suspecting improper pressures.
How does one go about setting them ? ... and to what value ?
Again, I have never been able to find these specs anywhere.

 

Those 3 wire boards were a hit and miss affair. They would work just fine when tested, then fail, then work again. Drove many a V12 owner/mechanic to drink.
The 4 wire were so reliable, and were the retro by the hundreds.
Getting hard to find now, but they are out there. If yours is a 3 wire I would seriously raise that trigger board near the top of the "to do" list.

Setting the FPR's, oh my, it has been a very long time.It is a fiddly adjustment.
Last time I did them, (hers), and the Sons, I used 2 fuel pressure gauges, and fitted 2 T pieces in the flex lines just before each FPR. The 2 gauge were attached to each T piece. Start it up, let it settle a bit, release the locknut on each FPR, and rotate the central bolt SLOWLY, Inwards raises the pressure, and outwards lowers the pressure. I set "hers" at 29psi, but the Sons was set at 30.5psi. Each engine is different, so a little bit of "playing" with the pressure is required. Think of that bolt as a mixture screw of a Carby.

Then there is the MAP sensor, mounted on the top radiator panel on some cars. It is a round alloy chamber, about 3" in diameter, and has a vac hose attached, and a wiring plug. This jigger converts vac signal TO electrical signal for the ECU, and has a bellows inside, like a Barometer, and they fail. Almost impossible to find these days. Some have repaired them with success, some have not. The same thing is used on Merc, some BMW, some Volvo, Citroen, etc cars, Basically anything that used the Bosch D-Jetronic EFI system. I found a Merc one for "her" car, still on it today. The fuel mixture, etc will be all iffy if this little sucker fails.

HT leads are a problem, so run the engine in the dark, and see how good the display is, you might be surprised.

 

Warning, He does bite. But only softly these days if you don't listen carefully.

 

ooooooh, I'm listening... and learning ! ( hey, if you want to know about 348 / 409 Chevys... well, that would be me ! )


Confirmed... my car has the "3 wire" version.


Fuel pressure ?
Trouble is, at this point, I can't get this engine to sit and idle... it's THAT bad.
I DO need to get an idea where the pressure is though.


The MAP sensor...
If it was bad, I take that one way to tell, would be a vacuum leak inside.
I checked this... and when apply vacuum to the hose that goes into it, there IS a minor internal leak ( unless it's through the hose itself ).
I'll see if I can confirm this tomorrow.


Fantastic information, guys... VERY much appreciated !


Now, if I could just get to a nice, simply page that shows all the tune up specs for these series II v12's

 

OK, I have found all my scribblings on the D-Jetronic system.

I will have a few drinks, and compile it ALL in a Word Doco and post on here. If it ends up too big, I will ask for your email address via the PM mode here, and I will send it direct.

If it goes that way, I only ask (demand really) that this post is kept updated for others in the future.

Be back soon, I hope.

 

Definitely sounds like gummed up injectors, I had the EXACT same issue on mine after I bought her as a non-runner. I run a different system to you, but I would guess the symptoms to be the same / similar, and mine had lost 6 cylinders in total (6 clogged injectors after the "experts" had finished blocking them up with dirty fuel) you may also want to look at flushing the rail with a cleaner of sorts.

I have also had a fine filter installed just before the inlet side of the rail as even with a new filter in the boot, her lines were repeatedly clogging the injectors. Haven't lost a single injector since.

Best of luck.

 

Here ya go.

My scribblings decoded, and I am still sober, HA.

Any questions, ask, i will have the info somewhere.

D Jetronic Jaguar info.doc

 

Grant:


Absolutely masterful. Although, I no longer have a car that uses that system, I
have saved it and printed it, just to read and enjoy.


Or, in the future, who knows!!


Carl

 

Well, my computer can't open that file... but I'll get around that.
Thank YOU, Grant, and Nathan.


I will now hide for a while, and try to sort this out.

 

Good guys.

Grant turned me on to drinking just last year. Now at 59 I suck down 10 beers a night. Thank you Grant.

Here's what I found on my pal's 77 XJ12 that Grant and all have been helping me with over the last two years.

EGR valves would open whenever the hell they wanted to. 10 seconds after cold start for example. "BWAAAAAAA". Fail. Under air cleaner towards firewall. Pipes can be broken. Hoses can be broken. Unit can be serviced (adjusted) but I opened the end, crafted a plate that seals off the exhaust entering the throttle body and put them back together. Good night on that one.

Poor cold start. Clean cold start injector connections. They are right at the two fuel pressure regulators. Test resistance of thermotime switch when cold. It's on the passenger side, six inches in towards the center of the engine from where the air cleaner box meets the air cleaner intake snoot.

Fuel pressure regulator. Right at the regulator there is a hose that feeds fuel to the cold start valve(s). Pull the hose off with a rag wrapped around it to catch fuel. Get a simple fuel pressure gauge. One with a nipple/fitting that will fit into the hose end that feeds the cold start valve. Clamp it down. In short, start car, observe pressure. Have a friend read the gauge while you feather accelerator pedal. Should be 30psi or 2.1bar all the time. NO FLUCTUATION. Any fluctuation over a couple of PSI and you need to spend the $60-80-ish and get a new one. One of mine was swinging 15 psi in both directions like a demon. Pretty cheap actually to replace. Loosen base 13mm nut, turn adjuster screw with 10mm to change pressure. Grant liked about 29psi if remember. It's pretty sensitive. Just today I reset and if I went to 28 it would falter.

Timing. You probably have a vacuum retard pod way down there in the valley at the base of the distributor. Assuming US and Canada are the same specs. Your timing is ZERO at idle with retard. Pull the hose and plug it (if you have an hour and long-*** needle nose pliers) and your timing should then be at 10 BTDC at idle.

Like Grant says, do the late night dark test. There may be some easy snakes to kill.

I have all the tune up specs and "stuff"

 

1977, 20k miles.

 

I do not have MS Word at the shop so I can't pull up Grant's .doc file. I do at home. I will pull it up and attempt to convert to an Adobe PDF file and post.

Grant is a wealth of experience.

 

Hope the attached works.

 

Thanks Bob.

Yep Jaguars, drink, warped sense of humour, drink, vocabulary extension, drink, adventurous spirit, drink.

PRIME requirements for Classic Jaguar ownership.

ANYWAY, i forgot something. Not EFI related, but something I have had over the years.

Under the trigger board is a large plastic wheel, with 12 "dark coloured" inserts around the perimiter. These are "Ferrite rods" and they are what triggers the reluctor that supplies the spark. Now, Lucas in their wisdom, drilled these holes all the way thru the wheel, and inserted the 12 "rods". All sweet for many years, then old age strikes, and the "rods" simply fall out, OOPS. There was a "fix" of sorts years ago, that required the wheel to be removed, and turned upside down, and a drop of "Glue" applied to each "rod" hole, allow to dry, refit and drive on with all 12 cylinders doing their thing.

Maybe not the problem, but well worth a look in my opinion.

 

Yep, he got me sucked into the JD thing......it works well.
I was partial to a bit of a drink before, but when the instructions include "take a drink"..............
Who am I to argue with the wizard of oz. My teachers always said on my report cards I was easily led.

 

Wow. I got special notes, too. Mine were like, he does not apply himself to the level of his ability.

With drink, application and my ability are pretty much aligned. Least I got one thing right.

Here's the resistance for the air temp sensor based on ambient. From the manual.

C Ohms
-10 960
0 640
10 435
20 300
30 210
40 150
50 108
60 80