Hello all--

I recently purchased my first Jaguar, a 97 XJ6 with 180k miles on it (engine was apparently rebuilt 60k miles ago though).

So the issue I started noticing after I purchased the car was this: The car has long cranking times only when the engine is warm. It will start up cold almost instantly, and if the engine's hot and I shut it off for less than 30 minutes it will also start right up. But if I leave it anywhere from 45 minutes to 2-3 hours, it takes a good 5-7 seconds of cranking, whereupon it will eventually fire up. I live in Florida, and the problem seems to be worse on hot days (though tonight was relatively cool and it happened again). I thought initially it could be vapor lock, but there's no pressure in the fuel tank when I twist off the gas cap (unless the vapor lock is in the fuel lines).

Car idles smoothly and no hesitation on acceleration, so I'm not sure that a tune-up would help (though I don't know the last time it was tuned up). Car has not stalled ever. I had the fuel pump replaced, but that didn't seem to fix the problem. Any ideas? I took it to my mechanic last week, and of course could not duplicate the issue.

Though I can live with the problem for now, I'm worried one day the car will leave me stranded. Thoughts would be much appreciated!

strat954
1997 X300 180k miles

 

A few things I have found with mine, in no particular order.

Fuel filter, maybe done when the pump was done, should have been, so worth a look, and cheap enough to do anyway.

Cam angle sensor (that wizzy thing where a distributor once lived) is mis-timed, and that is COMMON. Long cranking is the "normal" symptom, but usually EVERY start time, so again, simple enough to check, ask if you know not how to do this item.

Spark plugs are just plain OLD.

The dreaded "black goo" is built up in the throttle body, simply wipe it out with a solvent soaked rag.

Many other items may pop up, but those are a start and cost basically ZERO to eliminate.

 

I have the long crank time issue, probably should have been more curious about it when examining the car but it didn't seem like a big deal since it did eventually start up every time (still always a brief panic about it).

So, any advice for a total novice on checking the cam angle sensor and where to find the throttle body would be appreciated!

 

Hi , @strat954

The long crank issue that you explain can be also a leaking injector issue . When the engine is hot , within 15 minutes , you can start immediately but if the car sit for more then 20 minutes and don't start , the amount of fuel leaked from one or more injector , will make "rich " combustion chamber ( like engine flooded ) and the start will take longer ... injectors are always pressured even you stop the car, the fuel line will have high pressure ( maybe like 30 PSI ) and injector fail will be the reason for long cranking ...

 

Kerem may be onto something....but I'd expect a bit of stumbling and bumbling as soon as it starts if it is due to leaking injector(s) until the flooded cylinders are cleaned out. Another possibility, your Fuel Pressure regulator may be letting the fuel pressure decay when it is hot.
Further on Grant's cam angle postulate - perhaps properly adjusted but an intermittent fault when hot?
One last thing not to neglect, your crank-angle-sensor; again, it would be an intermittent failure at temperature.
Last thing I can think of: Make sure your engine grounding strap is clean and tight at both ends.