First post - Hello to all.

I am helping my friend repair his LHD 1978 XJ12L. I am a Jaguar noob. The car is an absolute cream puff, unmolested, a total garage queen with less than 30k miles He is in the Oil City, Pa area and keeps the car in a humidity controlled garage. I have seen only a dusting of surface rust under the battery.

I will get to the point. He has had some operational issues and the semi-local shop (Pittsburgh area) say that his ignition control module is not functioning correctly. The information I can pick up through my pal is that the shop says there is an upgraded ignition control module available and they are going to look for that for him. That was three years ago.

I want to get him on the road again.

My questions

1. Is there an upgraded module? Where can I get one? Why is it superior?

2. I see a box with cooling fins right in front of the distributor - what is it? Is that the module. Please forgive ignorance as I have no reference data currently. If it is not the ignition module - is it a capacitive discharge unit?

2. I see a Haynes manual available on Amazon.com. Friend has no reference books. They are usually ok but is there a superior product than wont break the bank?

3. He has gas dripping out through his charcoal canister when he stops the car. Is this related to the ignition module? I suspect not and I will search the forums after this post.

Just get me pointed int he right direction. Many thanks.

Bob

 

That model, and what you're describing, should be the "Opus" ignition. Not one of Jaguar's finest moments. For upgrades Google "Reopus" or "Re Opus" without quotes of course.

Fuel dripping from the canister sounds like a problem with the fuel return system...but I'm not really familiar with the system on that model. On later models a fault with the return valves allows fuel to be returned to the wrong tank ....and it eventually overflows into the canister. Might be worth investigating.

Haynes is better than nothing, but just barely. Too many models crammed into one book, usually, with important differences not mentioned. Find the genuine Jaguar manuals. Ebay and Jag parts specialists are possible sources. Even the factory manuals are not the greatest but are better than Haynes.

Cheers
DD

 

Great info DD. Was the comment "Not one of Jaguar's finer moments" directed at the Opus or the car or both. :-)

I was all set to dig into a Bosch system then found out the transition did not take place until the early 80's. Bummer. The Opus info does get me pointed in the right direction. The return valve system info gives me something to search on.

I also have not dug deep into this site for tech info.

Thanks much for the info and I will report back as progress is made

Regards,

Bob

 

It was the Lucas Opus ignition system. Even Lucas mechanics inserted an 'l' into the name - Oplus, (gettit !). What you have described is the box for the system linked to the distributor and coil. Early cars had the box in a daft position where it got all the heat, and this was moved on later models, but if yours is a 78, it should already have been moved out of the heat zone. Best of luck finding spares.

As regards your fuel issue, there are three valves involved in the fuel system. One in the boot switches between tanks for the fuel pump to draw upon, the other two are one each side of the car at the back of the rear wheel arches which work with the supply valve to ensure fuel is returned to the tank being drawn upon. All controlled by the changeover switch on the dash. The supply valve can stick, but the other valves switch the return over, so fuel goes to the wrong tank, and if this is full, the fuel has to go somewhere ! The return valves can also fail, so suggest you remove all valves and check for correct action.

 

Thanks Fraser - I think the fuel issue will be easier to tackle than the Opus.

This car has the original amplifier setup, unfortunately. I don't think other durability upgrades have been tackled either. One of the downsides to a garage queen.

I have found the amplifier box for sale but certain this is not the best answer over the long term. The aftermarket optical systems may be an option. I see nice write-ups on how folks have done these upgrades but then nothing found for sale. (e.g., Crane). Hopefully, it is just a matter of digging.