If the B bank cat is glowing red hot, that is because unburnt fuel is burning inside it. This sounds like the classic Marelli one bank failure. I strongly suggest that you must read the Great Palm's book where he deals with this phenomenon in detail and do his fixes before running the engine again.

You think you have ignition on both banks, but you probably do not, spark apparently there or not. If you disable the bank that has NOT got the glowing cat, I bet the engine will stop.

Greg

 

I would be removing BOTH cats for now.

Use a pipe or whatever to reconnect the system.

Once its sorted, make the HUGE decission to either refit the cats, or leave it like it is.

I know the O2 sensors "may" give grief, but that is sortable I reckon.

 

thats why we get them for FREE, problems from mechanics in over there head.

 

I am more along the thought process that maybe the damper has slipped? The timing fingers maybe are out of alignment? Very bad timing in both spark and fuel delivery, causing a very lean condition, causing the glowing left bank. My 71 V12 was in no way anything Marelli, but when I advanced cam timing, one side glowed cherry red, while the other side didn't. I don't think the engine has jumped time, but finding out if the timing mark lines up with the mark on the engine while at TDC 1A while in the compression cycle, would be a great place to start

 

percieved value,haha! Dreamers. Check out this XJ6.

1974 Jaguar XJ6 Sedan | Cars, Vans & Utes | Gumtree Australia Stirling Area - Inglewood | 1062003968

 

Timing fingers are located with three bolts and a roll pin and are attached to the centre hub not the rubber mounted outer ring so short of a sheared crank key there is not much chance of slipped timing.

 

Probably still a good idea to grab a light and verify timing given the entire ignition system is such an unknown on this car

 

Today's progress:

Today I took Greg's advise and pulled the A bank HT lead. The car wouldn't run. Then I reversed the test and unplugged B bank. The car would stumble for a few seconds then die but you could tell it was trying, unlike when the B bank was hooked up solo.

Then I pulled both banks so there was no way it would start. The car cranks smoothly and evenly. Correct me if I'm wrong, but IF it had jumped the timing chain, it would crank unevenly due to the compression cycles being all screwed up?

Tomorrow I will pull the cap and do the marelli mod. I'm not holding my breath that this is going to solve the whole problem, but at least I'll know that it's done.

I have determined both the coils and power modules are ok too by flipping them between banks and the issue stayed on the B bank side.

If time permits I'll grab a light tomorrow too.

Today one of the '88's wheel bearings started howling. The old girl must be getting jealous of all the attention its now NOT getting..

 

Great news. FWIW, I would change the plugs and HT leads at the same time. I am sure the mechanics of the car are fine. Soon be sorted with any luck, and good for you getting such a bargain!

Greg

 

I have said so many times to forget the "Marelli" mod. The Marelli rotor meltdown is IMO caused by lack of maintenance, mostly not replacing the front 4 spark plugs.

After my car sat up for a year when I was rebuilding and re-painting, she was only running on 8-10 cylinders and very rough, cleaning the plugs (they were new just prior to the layup) fixed the problem.

Pull ALL of the plugs and replace them, check the gap before installing, if its wrong the car will run rough. Pull the Dissy cap and check the rotor and cap terminals. BE AWARE the ignition lead sequence on the Marelli Dissy is different from the Lucas. It is common for people to install the leads in firing order around the dissy on a Marelli car. I can not remember the exact sequence but the Cylinder number is printed on the Dissy cap.

Pull all of the injector connectors, turn on the ignition (Don't crank the engine) and check for 12volts on BOTH terminals if the plug.

See how you go with this and let us know.

 

FREE ha ha...you can get Ebola for free too! Then you and your car will overheat.

 

I'm certainly not an expert here but here's my few weeks of experience...

Check out your wires. After pulling everything out of my car and actually looking at the wires it was really easy to figure out why my care was misfiring. Every single injector wire lacked insulation. Furthermore, I found this in the loom as well and I had a pin that was touching bare wires in the loom with the "wrong" injector... 5 and 4.

I suspect that when my car got hot the wires would get close enough together to jump. I'd pull the connector on the main harness and check the continuity on each of the injector plugs against each pin. Maybe you're not just misfiring but flooding constantly on 1 or 2 on that side. I'd also pull your injectors to make sure that they actually work.

 

This is not the best way to find shorted injector wires unless you disconnect ALL injectors and the plug back to the ECU. For example lets say the injector driver in the ECU is shorted when you check for continuity at the plug it will show a short, where is the short.

Best way is to check for 12V on BOTH wires of each injector plug. The ECU switches the injectors to ground so with the ignition on you will have 12V on both wires.

The FIRST thing I would check is the ignition leads are on the correct output on the Dissy.

 

I REALLY don't think that sprocket jumped a double chain.

With both units in the back plugged in, do you have power to both points of the dizzy?

 

I am curious to see what happened with your car. Were you able to diagnose and determine the cause?

Did you get it running? What a great story about a "free" Jag. We all know that nothing is "free" when it comes to Jaguars but great story none the less.

 

Yeah, this thread needs updates!

 

Hi all! Sorry to let this thread get neglected for so long but I FINALLY have an update for you all.

I narrowed the problem down to the ignition but without any test equipment I was at a dead end. I took the car to the local Jag mechanic who is an expert in all things xjs. He put the car on a scope and found that all cylinders were dropping in and out randomly and found the power modules to be at fault. I was suspicious of them at the beginning of this adventure but had no way to test them.

He couldn't find any replacements so he is going to convert the car to a much more reliable non-marelli system. Yes I know I could probably have found the modules myself after he made the diagnosis but I've had enough of this car being dragged around and sitting in the garage and this seems like the way to go for long term reliability.

All in all it's not going to be that expensive especially considering how I got the car! I'll tell you guys more about what is being done to the car when I know plus how much it costs me in the end and a video of her running if I'm ever so lucky to see the day!

 

Your choice, but who I would disagree concerning the reliability of the marelli ignition verses the lucas

 

I agree. And those modules are not only available, they were offered on Fiat, other makes, much cheaper.

 

Agreed!

I would keep it Marelli, the un reliable part is in the person not knowing how to properly take care of the Marelli that is what makes them a problem...

Looks like to me you would take care of it...