last year I bought a 1981 Jaguar XJ12 V12 Vanden Plas, has 60,000km the guy I bought it from was either in the process of or finished installing a crane lifter ignition (from summit racing) he said he couldn't get ignition pulse. I picked it up about a week later and he had managed to get it running by running a wire that goes from the new ignition to the ECU. The car now runs way to rich if I have it running (outside) my eyes water from the exhaust I stopped running it after I found it was running so rich that I think there was gas in my oil and the chrome bumper had soot on it. I need help and I need diagrams of ECU and wiring harness any help would be appreciated

 

it should be Crane Cam ignition from summit racing

 

Welcome to the forum Ltarr,

I've moved your question from General Tech Help to XJ6 & XJ12 Series I, II & III forum. Members here with the same model will be able to help.

There's also several V12 experts in the XJS tech forum who may be able to help.

Graham

 

Cant quite make out from the photo if its a P digital or an HE, on the P digital the coolant sensor has an enormous effect on fueling, I had exactly the same issue and it was the wiring to the sensor that had broken causing the car to run very rich, have a look on the AJ6 engineering site and that will give you the resistance values for the sensor.

 

if the ignition system wasn't right for the car would it still run? and if it did run would it be rich because the system can only fire up to eight cylinders? not sure what the part # is but I don't think its the right one. is there any way that the wire he ran because he had no injector pulse was essentially a hot wire so now the comp is just constantly dumping fuel in the cylinders?

 

Couple of things for what its worth.

1) Looks horribly like a HE to me.
2) The "jump wire" also screams HE, as the Lucas Ign Black Box would have been removed, so NO shielded wire for ECU pulse signal.
3) The PreHE has a trigger board inside the distributor for ECU pulse, and is retained when using the Crane.
4) If it is a HE, then the Crane will not run it, plain and simple.

There is also a post on this same car etc in the XJ-S section, so maybe a "blending" of posts by Admin etc would keep is a tad simpler????.

 

I think you first need to establish what ignition system the car was previously running, my eyesight is not what it was and there are quite a few vacuum pipes in the picture which would indicate HE but the very last P Digitals had the HE style fuel rails whilst still retaining the OPUS ignition which used a direct feed from the negative terminal on the coil to indicate engine speed to the ecu. The later HE system used a screened feed from the amplifier for ecu engine speed. The change point was engine number 7p45000.On both set ups the coolant temp sensor has a major effect on fueling. If its an HE I would just revert to the lucas ab14 amp and twin coil set up, if it was Opus then you will need to do a bit of research, new kits are available but not cheap. Which makes me wonder if this is why the previous owner went down this route.
On a positive note if it is the Opus you have the 'holy grail' of v12's , ie flat head and 10 to 1 compression.
Again google AJ6 Engineering lucas efi, wealth of info on there, also invest in the factory cd manual , JHM 1122, about £25 which will contain all the wiring diagrams , good luck

 

are you talking in the middle of the engine? if so that's the spark plug wires the distributor is down between the V. and how could I tell if its HE is there somewhere on the car or block that it would say?

 

The engine number is best, as mentioned above, but the number is very hard to see. It's in the "vee", well aft. near the fitting where the oil pressure sender is.....as I recall. Someone will come along and correct that if needed.

I think Jaguar began installing the HE engines in around April-May 1981. Check your production date tag. It the date is months before April-May 1981 then you probably don't have the HE engine. If months later, then you probably do.

Are the spark plugs at a slight angle? That's another difference....but someone will have to come along and remind us if angled = HE and straight = non-HE or vice-versa.


Cheers
DD

 

With little specific knowledge, only generic, I would offer the following:


1. identify the engine precisely.


2. Contact a Crane tech for help.


3. Compare the original ignition to the Crane equipment. Understand how each performs, then compare.


4. As to the Crane unit firing only 8 when 12 need fire: Use an induction timing light on each of the 12 while the engine is running and see if it lights up each time. Spark delivery detection!!!


5. yes, I suppose odd things can happen with mismatched stuff. Injection each and every stroke rather than of firing only or spark each and every instead of the power stroke. And, in spite of these oddities, it might run, albeit imperfect.


Carl

 

Here we go, just had a look at mine to remind myself, straight HE, angled away from distributor pre he flat head.

 

do you recommend putting the GM HEI Module on the car to get around the expense? or should I bite the bullet and go back stock and just relocate it so it doesn't fail again?

 

The H.E. (High Efficiency) engine, with 11.5:1 compression (12.5:1 outside the US) and a swirl combustion head designed by Porsche expert Michael May, was introduced in July 1981 and indicated by the letters "H.E." on the back of the car in place of the former "V12" emblem. In 1986, the H.E. emblem was unceremoniously dropped and a V12 emblem was used once again, but the car still has the H.E. engine. If you have an engine laying around and need to know which it is, the trick is to look at the spark plugs. The plugs on the pre-H.E. are vertical, and relatively easy to replace. The plugs on the H.E. tilt toward the center just enough to make them a real pain to get a socket on. Also, the pre-H.E. plugs use a normal 13/16" spark plug socket, while the H.E. plugs have the smaller 5/8" or 16mm hex.


is that true??

 

Badges and junk NO. Different markets did differnt badging. Never been a real clear indicator.

The spark plugs are the easiest identification.

Also the injectors on the PreHE were predominately Dark Green plastic section. The HE are a light Tan colour.

 

The plugs on the pre-H.E. are vertical, and relatively easy to replace. The plugs on the H.E. tilt toward the center just enough to make them a real pain to get a socket on. Also, the pre-H.E. plugs use a normal 13/16" spark plug socket, while the H.E. plugs have the smaller 5/8" or 16mm hex.


is that true??[/QUOTE]


HE plugs do tilt in towards the centre of the V, use a metric 10mm plug spanner and are all pointing in the same direction.
Flat Heads the plugs are slightly angled forward for the front six and rearwards for the rear and use a metric 14mm plug spanner.
If you have an HE to revert to the original lucas amp has got to be the easiest and cheapest route.

 

Sorry forgot to add that the GM Hei is only one part of the jaguar /lucas amp, there are some other internal parts that may need replacing, there was a fairly definitive post by German guy on the etype uk forum.
My 1982 150k mile HE is still on its original amp, its only some brittle wiring that's needed replacing.

 

what do you think the jump wire from the ECU to the crane amplifier is for? and only when he attached that is when it would run freely without priming the cylinders manually but now like I said is to rich is there anyway a bad injector would make the computer over compensate for the bad injector by making it think its running lean so it would just dump more fuel?

 

No idea. I have some theories.

Until we all know, you included, if this is a HE or PreHE engine/system can we continue this discussion.

The systems are soooooooo different, and the systematic sorting is even more different/specific.