1975 Jaguar XJ-S

Thanks!

Here you go - its got the complete pre-He export nightmare. Exhaust gas recirculation, air injection, vapor recovery system and catalytic converters...

I had one for years, while there is 3x everything you would get on a 4cyl, none of it is that complicated, just need to be methodical.

would it be worth stripping most of that off and running it on a modern ecu?

You could, but Harry doesn't seem to much like playing with his cars - for instance I watched him failing to secure a loose wiper arm on that XJC, instead relying on Rainex. With the injection he got fed up of a misfire, and instead threw £10k at it -I don't have that money to play with!

I also have a decent knocledge of OPUS and Bosch D-jet injection, so I'm okay with making it work as it should - more of which you'll find below.


Anyhoo - on with things.

Faced with a non runner, the first thing I wanted to do was get some life into systems and see if it would turn over. A suitable battery was found, the engine checked to see if it would turn by hand (it did. Woo!) oil drained and refilled.. then turn the key.



No dash lights, gauges, or any kind of life inside the car, but the engine turned over in that familiar lazy fashion that only the V12 can do.

So working from the front I checked through the ignition system (all seemed good), injection trigger board, injectors click away, but there's no fuel. The fuel pump was comletely dead, the swirl pot and filter blocked and the tank had a residue of stale fuel in the bottom.

Filters and pump were easily acquired off ebay, but flushing the tank and other components made me very unpopular with my wife and neighbours due to the smell!! Eventually I was ready to try again.

A cough, a pop or two, then it settled down into a reasonable idle, with a slight misfire... I'd now got myself a running car.

It didn't last long. After that first start it became proressively harder to start,eventually giving up altogether. The OPUS ignition system had failed; I was pretty lucky in getting anything at all out of it before some transistor or capacitor in the amplifier unit committed electrical suicide.

So, we'll fit the later system off a V12 HE. It uses a Hall effect sensor instead of ferrite rods, a nice little General Motors module wrapped in a Lucas box, and rarely has ever let me down in 6 or 12 cylinder form.

This then creates a couple of issues for a pre HE car. It still needs the injection trigger board (missing from the HE, as it takes a signal for the injectors from the ignition module), and the vacuum advance mechanism is different.

So here's the fun... you make a hybrid distributor.

Take one slightly annoyed pre HE V12.



Remove all the tat off the top of the engine, to expose the old distributor.





Pull the top section off, leaving the lower (mechanical advance section behind. Now is a good time to make sure that this actually works, as its an item which almost always seizes and causes many V12's to run badly.





Next, get to breaker, get a V12 HE distributor (not the Marelli one) and dismember it. Old top section on the right, new one on the left. Swap the vacuum capsules over.



Refiiting, as they say... it all goes together how you would expect, as the casting is a slightly modified version of the older one. By leaving the bottom section in you haven't disturbed your static timing eitehr, so all we need is a trigger board for the injectors.

Luckily, the holes for mounting it were retained and used for a flash shield, so use that as a free and slighty odd looking frisbee, and fit the trigger board. Space it according to the manual, remember to fit the rotor arm that has the magnet to operate it, and then button everything up.



Fit the ignition module as per the manual.. and then start the car.




Total cost around £90, against £600 or so for a "reOPUS" kit. Despite the usual "it won't work/doesn't work." from some enthusiast club expert types, it has before and still does..

I remember when I first got mine (very early HE), the performace was nothing special, freeing up the seized advance felt like it released another 100hp.

It would be interesting to trace who the original buyer/owner and purchase price was - must have been someone pretty well-to-do at the time...

Interesting. Wasn't a certain Donald Trump or John Lennon (who moved to NY in 1971, I suppose?

Thank you! I think it still is underrated even now; once sorted they make a brilliant car for what you pay.



The iginition module will be exposed to the weather but one small tweak ( I mentioned in the Youtube video there's a few little bits to do) will be to seal up the joints and plugs with a decent silicone sealer to keep any moisture out. In terms of location; its ideal to keep the temperature low as can be.

The OPUS module started off in the vee of the engine - which is where I've put the dud one to maintain the original look under the bonnet, but there was a recall that placed it out front where I've fitted the Lucas AB14, and thats where mine was when I started this conversion.

If I have any trouble with it, I'll relocate it up onto the intake manifold as per the HE cars.