Welcome ,
Thanks for askign questions . Post '92 model years seem more reliable over pre Ford ere Jaguars .
I have a '93 XJ40 but I had a hard time to pick up mine due to poor reliability facts .
Fuel pump relays might cause problems as to failed to start the engine . Beware some rust issues too . Electric components require some dexterity as well

 

The engines in these are generally pretty bullet proof. Odds are most of those that don't start have ancillary issues.

The electronics on these can give you a skull cramp, but with a wiring diagram and some patience you can sort them out.

 

If you can find a clean 94, get that one. Some late production 94 MY xj40 had the relays updated, but still are the dreaded blue relays. If you get any xj40 93 or 94, and it has blue relays, replace all the blue relays on the firewall with the replacement sealed black Hella relay. Most of the starting issues are because of these relays, particularly the ones mounted on the firewall in the engine compartment. The fuel pump relay is behind the right side trunk carpet just forward of the right rear tail lamp assy, replace that one, too. It'll be blue if it's original or not updated.

Also listen for noisy fuel pumps on these old beasts, 93 and 94. If you hear that excessive buzzing noise inside the car when turning the key to the "on" position, be ready to buy a new pump. Some noise is normal, but loud is loud and means she's worn.

 

Hey blues how loud of a noise are you describing? Since I bought my car some 29 months ago there has been like a buzzing everytime I turned the key, or when I push the brake before shifting into Drive, and maybe when I turn on the radio at first. Is that the noise yuo are talking about? I've never figured out what it was, but it isn''t too loud or annoying, it is just a little quirky

 

They key on buzz is the fuel pump.....normal to hear it, but not too loudly. The buzz when hitting the brake pedal is the brake booster motor running to maintain boost pressure. The accumulator vessel on the brake boost motor is depleted. You will need to replace this. You should be able to get 4-5 hard pushes on the brake pedal before losing enough boost pressure for the motor to turn on.

 

I'm the guy who wrote the original XJ40 pages at Jag Lovers... wow, that was 12 years ago. When I wrote them the X300 was the current car, and XJ40s were still on Jaguar dealer's lots and you could easily drop $25k on a nice 94. Times have changed.

Anyhow, the biggest problem these days is that the earliest XJ40s sold in this country are over 22 years old and the youngest car is 15 years old. If it were me, I would simply buy the best 4.0 car that I could, as these cars are now old I would worry much more about condition and how the car has been cared for rather than a specific year car.

Realistically, you should avoid 88-89s, these were (no offense folks, YOU may have a good one and I did own a couple but this is simple truth) lousy cars when new and I doubt that 20-22 years has been kind to them. Now, if I found a nice 89 that had PROPERLY been cared for and had no major issues, I might be tempted, but you need to go in realizing that you have a car that even in nice shape has a wholesale value of $1,000 or less and is going to be needy.

By now I doubt there's many 88-93s left still on hydraulic suspension, but that's nothing but trouble, the diffs can act up, doorhandles, etc. But watch for cosmetics, the two worries are rust and interior as these can cost a fortune to fix and a rusty XJ40 is a parts car, period.

Find a nice, low mileage car that's been maintained properly and they are a joy to own, problem is, I would estimate that MAYBE 10% of the XJ40s on the road fall into that category, by this time most are on their 4th or 5th owner, generally someone who bought the car because it was in the paper for $2,500 and they want a flashy prestigious car for pocket change, the vast majority of people who buy them can't or won't properly maintain them, and it's understandable, one big repair and the car is essentially totalled. I know of a nice '91 Sovereign that was scrapped not too long ago because it blew a head gasket, that and the whining diff meant the car would cost more to fix than it was worth.