Jaguar XJS 6 Litre Starting Problems

Jaguar XJS 6 Litre Starting Problems

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Fat Fairy

Original Poster:

503 posts

185 months

Monday 6th April 2015
quotequote all
Afternoon All,

A little while ago I started having problems with my daily runner XJS

She cut out on me 'out of the blue', then refused to start. I diagnosed it finally to the Crankshaft Position Sensor, which I duly replaced - Car then working ok.

When driving, I noticed my battery voltage dropping slowly but surely. Workshop diagnosis said alternator, so alternator bought from the UK and fitted. Didn't seem to have fixed my problem, so very cross with workshop. A good charge seems to have improved matters.

Took car for its 'MOT', which it passed, but on the way back it suffered the signs of Marelli ignition failure, loss of power, leading to chugging like a tractor, and finally stopping with an Exhaust Temperature warning.

Since then I have replaced a full set of ignition leads (1 king lead open circuit; 2 open circuit, 2 intermittent open circuit, 2 high resistance out of the 12 leads); Rotor Arm and Distributor Cap (both with contacts looking pretty shabby).

I have started since then, but with difficulty. She still sounds like a tractor, as if only running on half the cylinders. I have good spark on both banks. Exhaust from both pipes.

Have I missed something obvious? I am assuming I have fuel flow as it is running, albeit at around 400 RPM.

Any ideas where I can go from here?

FF

tortop45

434 posts

159 months

Monday 6th April 2015
quotequote all
Get hold of a jaguar repair operation manual,the factory one to start, it well help you big time .When things go wrong with these v12 its the best place to look for fault finding,

Fat Fairy

Original Poster:

503 posts

185 months

Monday 6th April 2015
quotequote all
I had a CD ROM for the facelift, but it decided not to work on Windows 8.1 and is now b7ggered........... mad

jith

2,752 posts

214 months

Tuesday 7th April 2015
quotequote all
Fat Fairy said:
Afternoon All,

A little while ago I started having problems with my daily runner XJS

She cut out on me 'out of the blue', then refused to start. I diagnosed it finally to the Crankshaft Position Sensor, which I duly replaced - Car then working ok.

When driving, I noticed my battery voltage dropping slowly but surely. Workshop diagnosis said alternator, so alternator bought from the UK and fitted. Didn't seem to have fixed my problem, so very cross with workshop. A good charge seems to have improved matters.

Took car for its 'MOT', which it passed, but on the way back it suffered the signs of Marelli ignition failure, loss of power, leading to chugging like a tractor, and finally stopping with an Exhaust Temperature warning.

Since then I have replaced a full set of ignition leads (1 king lead open circuit; 2 open circuit, 2 intermittent open circuit, 2 high resistance out of the 12 leads); Rotor Arm and Distributor Cap (both with contacts looking pretty shabby).

I have started since then, but with difficulty. She still sounds like a tractor, as if only running on half the cylinders. I have good spark on both banks. Exhaust from both pipes.

Have I missed something obvious? I am assuming I have fuel flow as it is running, albeit at around 400 RPM.

Any ideas where I can go from here?

FF
You almost certainly have a blocked cat, possibly both. The symptoms you describe are classic and fully explain the high exhaust temperature. I think the ECU has shut down one bank to prevent fire damage as the excess temperature could ignite anything nearby in the engine bay.

I had exactly that same problem with a Merc 600 V12. I took the core out of the cat and it went like a scalded cat. (forgive the pun!)

J

Fat Fairy

Original Poster:

503 posts

185 months

Thursday 3rd September 2015
quotequote all
Well, after a summer of trials and tribulations, the XJS is back on the road.

The main culprit, apparently, was the Crankshaft Damper, which also damaged the Crankshaft Position Sensor, and the Engine Speed Sensor.

Along the way, the steering rack started to leak, so a new set of seals was sent for and fitted.

Once it started and was road tested, the overheating issue came to the fore. One re-cored radiator, a pair of thermostats and a repaired expansion tank later and all is now good.

A good blast down to Abu Dhabi and back and all is well biggrin Happy Days biggrin

Ps. Many thanks to David Manners, and Graham Hallet of XJS Stuff/Grubblogger. Some of the bits were getting hard to find.....

FF