Hello everyone,
This is my first post (and my first xjs)
It’s a 90 V12. There’s a mysterious looking vacuum looking line with a fuel filter on it. Runs from somewhere sneaky on the valley of the engine then comes out to the bracing on the drivers side of the bay. I’ll post a pic. It really doesn’t look factory to me but I’m really having a hard time finding what this is!
Also I will be doing the fuel lines and injector seals with the kit from mr injector UK so I’ll be taking more pics tomorrow when that’s all apart. If anyone has ever seen anything like this please let me know 
Just a thought could it be a vent from the transmission?
I like the thought. I can try and trace it a little farther in the daylight tomorrow but from what I saw it appears to run around the back of the engine and back to the front towards the distributor.
That is the vent line for ignition distributor.
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Yeah. That’s the vent filter for the cooling air being drawn through the dizzy.
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Fresh air supply to interior of distributor. Vapor vent to prevent fire.
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Here’s an illustration
Cheers
DD
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Wow that makes sense. Thanks everyone! Problem solved. 
Welcome to JL.
Being a new owner of a Marelli car and talking about venting the distributor, you are going to sleep much better knowing that the inside of the dizzy is spotless and you have the “right” cap and rotor.
I hope you’re familiar with the “Book”
Also, I spotted something else in your picture, pointed with an arrow here:
Your car has the Teves III ABS system, which is quirky. I don’t see it very well, but I am guessing the fluid inside the reservoir is dark. This is an indicator that it has not been replaced in many years and has absorbed moisture and other gunk.
This is a a MUST to do and the procedure for bleeding the brakes (rear) is far from conventional.
Lots of info on this subject in the Book and in the archives.
Good luck!
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Thank you for that! I’ll definitely be going through it. The fluid doesn’t look bad but I’ll be changing it. At one point in this cats life it was really loved. Service records have shown that. I bought it from the second owner who bought it in 1998. He also loved the car but he’s not much of a mechanic and our jag shop in town has since closed, leaving him a little helpless. This car was a rescue and I’m no stranger to strange cars. But I’m definitely going to take all the help I can get for this one and have fun learning along the way! Thanks for your help. It’s much appreciated. Cheers 
You’re welcome.
I see you’re in Sonora, CA.
There is a very clued-up forum member living there as well, look him up:
Paging @Ptipon
Howierodgers,
I see that you are new to Jag-Lovers. Welcome!
That part is the DAC4062 air filter for the cooling air pulled through the Marelli Ignition distributor.
I have found over the past two decades of Jaguar ownership that it is important to have the correct Jaguar Parts Catalogue for each of my Jaguars. It is very helpful in quickly solving mysteries like this and saves time and money while shopping around for the correct parts because you know the correct part number and nomenclature.
Attached is a picture of the cover of the Parts Catalogue that I have for my wife’s 1990 XJ-S convertible. I purchased it on eBay for about $50 and it is easily worth its weight in gold to me.
Other important documents to own and refer to are the Drivers Handbook, XJ-S Repair Operations Manual (ROM), Kirby Palm’s “Experience in a Book”, and S-57 Electrical Guide. I purchased all of my hard copies on eBay.
Paul
Thanks for the complement Steve. I sent Howie a message with my phone number. That makes 3 XJS members in Sonora. Looks like Sonora is becoming an XJS owners magnet. Pretty good for a total population of 50k.
I’m very familiar with the positive air flow requirement for the Marelli ignition. It was the only cause for a fire that I had way back in 2000.
Wow. If the guy isn’t suffering from Shipwright’s Disease already, you’re going to infect him remotely!
seriously! I think I’m already infected.
Just excited to drive this thing (hopefully soon)
