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help with cold start problem XJ6 Ser 3


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The problem: On starting from cold the car runs unbelieveably rich, has no power and throws out black smoke. The tailpipes have heavy deposits of soot. After a few minutes the problem clears and the car drives normally. There is no mis-firing apparent.

The car: 1981 Daimler Sov. VP 4.2L (XJ6) auto, air-con, fuel injected.

Can anyone point to what may be broken or need changing - the fuel injection system is very complex and my regular mechanic has no experience of the XJ6.

Thanks in advance for any light anyone can shed on this.

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Welcome to the club, Dave.

I am not a mechanical expert but a possible cheap solution could well be a clean out of the fuel system  ---   almost a touch of the chimney sweep.

The Terraclean Service which would cost about £125 would be beneficial and is done without disturbing mechanical parts or some Wynns fuel additive for fuel injector cleaner at about £8 is another way.

Have a look at the Terraclean Video on You Tube.



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Hi David -The one suggestion I will make is that it could be a leaking injector  ----It leaks into the cylinder

when standing Idle then when you start the car it has to burn the excess off causing the smoke etc .

Then its clear to run normally after.??


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Thanks guys. I'm already running with dipetane fuel additive to clean out the system and reduce particulates but that clearly isn't helping. My mechanic suggested the coolant temperature sensor for the fuel injection - which is on order - but there are a lot of other sensors, valves and bits & pieces in the injection system :wacko:

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Hi Dave,

I have a similar problem with my 08 X type diesel. Its been into Jaguar and they couldn`t find the problem (no fault codes showing) The problem is getting worse and its going into local garage next week. They think it is either a faulty sensor or leaky injector. I will let you know what the outcome is.



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  • 2 years later...
On 6/3/2016 at 5:40 PM, Dave&Fran said:

Hi Rod,

Would appreciate any info you can provide.



Hi Dave,

To help one needs to know are there any other symptoms, other than bad cold starting and a sooty exhaust...Once running at operating temperature does it run clean and strong?

Whatever the cause is, DON"T go buying parts unless based on factual testing to determine cause and effect otherwise you'll end up broke and !Removed! off with your beautiful XJ.... 

Attached is a PDF that'll give you a better understanding as to what happens when you attempt a cold start, along with how to check each function. 

I sincerely would like to give credit to the author (I think on Jag-lovers.com?) but can't recall the name or source..


XJ6 Cold Start Check.pdf

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