Hi Guys

I was reading in 'Kirbys Palm' how easily a fire can start, if one bank of Cylinders (The 'A' bank I believe?) decides to shut down while still pumping fuel into the hot exhaust! (caused by the Marelli distro spark burn through)

It was saying some thing about filling the Asterisk shaped hole with silicone sealant but as I've never taken the Cap off and I do not have as much mechanical knowledge as you guys.

I didn't quite get what he (kirby) meant.

Does anyone have a photo, that clearly shows how you fill it up with sealant and where it goes.

Just an idea, that may not work but would it be any good to drill a hole in the exhaust system somewhere to allow any excess fuel to drain off, to avoid it catching fire if one 'bank of cylinders' shut down.

As I've said I'm not a mechanic and am only learning this stuff from the help you guys are providing on this forum.

 

It really is very very easy, really... With the Marelli, you can pull ALL the plug wires with reckless abandon. As long as you make sure to put the coil wires back properly, putting all of the spark plug wires back on is almost brainless, as long as you know the numbering of the cylinders. 1A on right front, going 2A,3A, 4A, 5A, 6A front to back on right side. Ditto on left with exception of it being the B side. Look at your distributor cap. It tells you what plug wire goes to which cylinder right on the cap. Pull all the wires, then the cap comes off really easy. The rotor button is held on by two allen head screws. Look at the way it is pointing, making sure to note the which way the high contact on the rotor is pointing, because it will go back on either way. Once you pull the rotor, just put some silicone up in the void where the rotor sticks onto the distributor shaft, reassemble, and that problem is most likely over.

I doubt drilling a hole would allow fuel to drain even if it were a good thought. We aren't talking gallons of fuel. We are talking a small amount of unburned fuel going into a cat that is FAR beyond the combustion temp of gasoline.

 

I have had my Marelli car now for 7 years ( its a daily driver) and have not had the infamous Marelli issue. I believe it is caused by lack of maintenance. If the spark plugs are bad then this will kill the ignition leads then the only way to ground for the spark is via the rotor.

Replace ALL the spark plugs at the required interval and I believe you will not suffer this problem.

 

I would expect your car would NOT have cats being a UK car, as I understand it the cats are a major part of the problem.

 

I am the guy who sent Kirby my failed distributor cap for the write up. My '91 is long gone now (wore it out) and moved on to the XK8, much better car in my opinion. I am surprised that there are still any Marelli caps around as they were difficult to find years ago. Make sure it has brass posts for the spark plug wires and has the weight. The replacements are real junk. The problem with the "meltdown" was the connection between the rotor and the cap. The spring in the cap gets weak and the rotor is not forced down for proper contact. This is as I recall it but it has been years so I may be wrong. V12 forever!!!

 

Thanks

For that really good advice, which is appreciated.

 

Make sure the hoses and filters to and from the distributor are good and clean.

Mine were all brittle and cracked. The "L" connector under the left (bank B) intake to the extra air valve was clogged up and the filter on the left wheel arch (sits along the strut bar) was never changed...

Replaced the hoses with silicone ones, unclogged the L connector and the filter was new. Result is, it should work better than before

 

Thanks Warrjon

That is very reassuring, great advice!

 

Hi

My XJS does not have Cats, so maybe I will be ok after all and just have to keep up the maintainance.

Thank You for your reply

 

Hi Laureb

A bit of 'History' there then.

Each to their own but I would never consider trading my XJS for any other Car. V12 forever+1

 

Thanks Daim

I will check that out.

 

I have stuck mainly to just basic maintenance on my XJS V12. My spark plugs only have around 5K miles on them(dealer installed by the last/original owner at 27K miles) but I have thought recently about doing the rotor silicone squirt. I still have the original cap and rotor but am not very excited about removing a bunch of stuff to get at the distributor cap and to remove it.


Do any of you have a step by step process of what to remove to get at the cap and to remove it? I am pretty handy but with this car I am very reluctant to screw anything up. LOL. Thanks.


John

 

I am the 3rd of my car and it was dealer serviced, the front 4 spark plugs looked like they had not been replaced for some time, the other 8 were good.

These plugs require the AC compressor to removed to replace so I think they do not get replaced every service. Pull 1A or 1B and check it.

To get the Cap off you need to remove the spark plug leads from the cap, undo the screws securing the cap and remove it. BE AWARE that the plug lead order on the Marelli cap is NOT the same as the Lucas, the cap has the plug numbers molded into it.

 

I know how to remove a distributor car(once I get to it), but I have a 1990 V12 and the cruise control stuff is on top of the cap. I think I have to remove that first but I am not sure the process/steps to do that. Anything else have to be removed?


Also, if you remove the cap, do you have to replace the distributor cap gasket or can you reuse the old one? Thanks guys.

 

Gasket is needed new. Never reuse gaskets. You don't use condoms twice... That is how I was taught...

And the Cruise actuator is bolted to the ac compressor. Remove the center screw and done

 

in a year or two I will be re engineering the system to use these coil packs and no distb.

 

I have been reading about this and fear it so while I have a bunch of stuff apart I want to try to do it.

I took some pictures-

first one is distibutor cap with HT wires off.
second one is distributor cap off.
third one is with rotor off.
fourth one is with a magnet on what I believe to be the distributor shaft.
fifth one is the underside of the rotor
sixth one is a pencil pointing to what I believe is supposed to be filled with silicone.

So- basically you grind down the distributor shaft in picture 4 to level with the base that holds the allen screws that hold the distributor rotor on?

And then you fill the underside of the rotor in picture six with silicone?

and that's it right?

 

yep

u got it

don't forget a new gasket under the dizzy cap ,

BB

 

Great Info! with very useful pics and 'how to' instructions, please could you put some more pics up as you go through the process, for instance to show the method that you used for grinding down the Shaft.

As I for one did not think that grinding down the Shaft would be essential, although probably more desirable if you can do it.

Did you have any problems getting a New Gasket and Rotor, or come across any problems on the way?

 

It looks like you can cut the shaft to shorten it, but that gets me a little nervous. LOL... Grinding it may make a heck of a mess and I would not want any metal particles to get down into the distributor...