New to the V12, and this site, Daimler Double Six

(Kim Wylie) #1

Hi All,
I’m new to the site and glad I found something that is so specific to us V12 owners. I’m British and live in the South West of France, and by day fly another British iconic brand as a living. Hawker once made the Hurricane which helped save Britain during WW 2, but now the venerable HS125 keeps business executives warm and ‘comfy’ and bread on my table and a few cents in my pockets so I can pump even more CO2 into the atmosphere on my days off by thrashing around in my V12. This brings me nicely onto the reason for this post.

I bought yesterday, a beautiful Daimler Double Six, otherwise known over ‘the pond’ as a Vanden Plas. I drove it for the first time the 350kms from the showroom to my house and I noticed on arriving that even though it had a good workout, at idle, it tends to slightly miss and judder as if one or two of the 12 are not working all the time. I had new spark plugs fitted before leaving the showroom so these are out of the frame. And yes, they did replace pots 1 and 2 (underneath the air con unit) but it still I have this slight hesitation and missing. Any basic ideas before I take it to the experts?? I am thinking HT leads, vacuum problems, maybe it’s running a bit lean (the old plugs were a bit white), coil problems, anything I can suggest to the expert?

Thanks for your suggestions!!!


(Kirbert - author of the Book, former owner of an '83 XJ-S H.E.) #2

Actually, the Daimler Double Six is known in the US as a Jaguar XJ12. In the US, a Vanden Plas is a 6-cyl saloon with a package of options. I think. If I’m incorrect, I’m sure somebody will correct me.

(Paul M. Novak) #3

Well, sort of…

This is how I understand it, and I own a Canadian market Series III 1990 V12 Vanden Plas (essentially a Daimler Double Six badged as a V12 Vanden Plas for the North American market).

Jaguar made Series III XJ6s and XJ12s at a variety of trim levels for a world wide market. The “basic” cars, called “XJ6” or “XJ12”, had the lowest level of trim and options. Then there were models like the Sovereign that had a higher level of trim and options. The Daimler had the highest level of trim including all available options, especially the Daimler Double Six with the 5.3L V12 engine. Due to legal limitations over the use of the name “Daimler” in North America, the name Vanden Plas was used for that market instead. Vanden Plas being a European coach maker for royalty that Jaguar purchased.

In the 1970s, when Corporate Average Fuel Economy (CAFE) limitations were imposed in the USA, Jaguar decided to only sell the XJ6 and not the XJ12s in the USA to meet CAFE requirements. As the demand for higher levels of trim for the XJ6 increased in the USA Jaguar badged those cars as Vanden Plas to distinguish these higher level trim packages from the basic XJ6. The USA market Vanden Plas cars were all six cylinder cars. The only way that XJ12s or V12 Vanden Plas (like mine) made it to the USA was either by a USA serviceman bringing one home from an overseas duty station or someone who went through the Federal EPA and state requirements for legal import. This are also rumored to be a small number (12?) of XJ12s sold in the USA before CAFE limitations hit and these XJ12s are mentioned from time to time on Jag-Lovers.

I hope this helps to further confuse the Daimler Double Six vs Vanden Plas vs XJ6 vs XJ12 matter. :wink:

I have owned two XJ6 Vanden Plas and one V12 Vanden Plas as well as three XJ6 parts cars (one of them being a Vanden Plas).


(Philip Lochner) #4

It might be running a bit lean. Easy way to test is to

  1. pull off the intake air temp sensor on the LH air cleaner. This causes the ECU to think that the air is colder and enriches the fuel mixture - but not hugely so;
  2. pull of the vacuum tube from the LH fuel pressure regulator on the fuel rail and plug it. This will enrich quite a bit and depending on how much more, may actually CAUSE the symptoms.
  3. a third method is to pull the vacuum tube off the ECU and attach a temporary tube that you can suck on. The more you suck the less fuel it will feed the engine. The objective will be to see if you can find a level of vacuum that will eliminate the missing;

It might be spark related:

  1. a weakish spark - does it have the auxiliary coil mounted on the radiator?
  2. spark too far advanced. You may have to investigate to what extent the whole ignition system is modified or not;

All I have time for now…

(John M Holmes) #5

Hi Kim, You might be interested in Paul Clarksons site .He has sold the car , but keeps the website"open".

(Paul M. Novak) #6

What model year is your Daimler Double Six? I looked at your Jag-Lovers profile and it says: “Daimler Double Six, 6.0L V12”.

Did you mean to say “5.3 L V12”, a Series III saloon with two fuel tanks, Or do you have the later XJ40 style saloon with one fuel tank?

I just want to be certain of the body style and engine of your car before I start making recommendations about what to do about your issues. I have two 5.3L V12 Jaguars and do.most of the work on them myself but I don’t have any experience with the 6.0L cars.


(Kim Wylie) #7

Hi Phillip,

Thanks for your reply - I will try this and let you know!! But I’m off to work now and it will be a few days before I get to the car again!!, H

(Kim Wylie) #8

Thanks John - I will check this out! H

(Kim Wylie) #9

Hi Paul,

It’s the XJ40 style car (X305 I think it’s called) and I have attached a recent picture to be absolutely sure and the MY is 1995.

Thanks H.

(Paul M. Novak) #10

Your 1995 Daimler Double Six is even more modern than I thought. The XJ40 body style with a V12 is referred to as the XJ81 but your X300 body style with a V12 I believe is referred to as the X305. This is two generations newer than my 1990 V12 Vanden Plas (Series III Daimler Double Six).

In order to avoid confusion I recommend that you always include your model year when posting since your car is significantly different than the earlier Daimler Double Six cars.

In addition to the Jag-Lovers "V12"list you might find help on the “X300” list where you model year is discussed.


(Steve) #11

This is a 6.0L. But…
In France (and outside US), this might be called MY 1995 – based on production date – but in the US, it could also be MY 1996. Does it have a distributor or it is the Nippon-Denso ignition with individuals coils?
If the latter, you might not get much help here – I do not recall seeing a post regarding this V12 engine set up in years.

If you have a dizzy, and you have a stumble at idle, just look up some of my post in the archives on this subject.

Congrats on the purchase!

EDIT: I had it wrong. It appears that all X305 had the Nippon-Denso ignition. I had wrongly assumed that since the 1996 was the first year of OBD-II, only the 1996 were without dizzy, but it turns out that both 1995 and 1996 were the same. Apparently Jaguar XJ12 was never fully compliant with the OBD-II standard, although a simple scanner might be able to read some of the codes…

(John) #12

Hi- it’s a little hard to tell because of the angle, but I think yours is a 95 SWB. The 96 has an exaggerated longer rear door. I just got a 96 XJ12 myself! It was $900 so I couldn’t pass it up, even if it needed two fuel pumps to get running again. There are several X305 owners on in the X305 section if you want to try there also. They didn’t make many 12 cylinders in 95/96 so traffic is light, but someone should be able to help there. -John

(Steve) #13

$900 for a complete car? WTH!!! On the XJS list, there is a running thread where someone paid $900 + shipping just for the turbine wheels. You’ve done well!!!

BTW, if the sedan uses the same two submerged fuel pumps as my convertible, it is NOT that big of a deal. If you don’t pay labor, two new pumps will be $250-300 at most.