There was only one engine available in the US in 1990 models - 5.3 liter V-12 HE, does that help?

Cheers

 

Well, since it's a 1990 V12, and not an XJR-S, we know it's a 5.3 liter.

Since it's a 1990 we know it's Marelli ignition

Since it has Marelli ignition engine we know it's 11.5 compression

Assuming it was originally sold in the USA it'll have cat converters

Does that help?

Cheers
DD

 

FYI, the actual engine number is invisible, engine in car. It is at the rear of the block, just forward of the transmission/engine join. See post 2 on this thread for more info:
https://www.jaguarforums.com/forum/x...decode-133597/

The actual engine number when the change in V12 XJS ignition system from Lucas to Marelli occurred is believed to be during the 1989 model year at (or around) VIN 156989. But the "model year" has all sorts of meanings, so the VIN number is the best guide. If your engine has a distributor that looks like this with two king leads in the cap, it is a Marelli ignition car:

If it looks like this it is a Lucas ignition car (the white tube on top is a ventilation outlet)

 

 

It is *possible* to see the engine number with the engine in the car. As stated above it is located in the "V" on the top of the engine right ahead of the transmission bell housing. But it will likely be completely covered in oil from the hard oil lines that run above it and always leak. I sprayed some engine degreaser down there and took a long flathead screwdriver and scraped the oil and dirt away, and with a bright flashlight was able to read off the engine number; I'm sure you could do the same. I then printed out a label with the engine number and put it on the side of the engine bay so it will always be there if needed.