Got to thinking even more. (Up to about 2 hours total)

Even though the new problem started with the new coils, maybe there's nothing wrong with them or any of the work you performed. Perhaps the new coils draw a bit more current than the old, but are still within specs. Consider an existing fault somewhere in the circuit, such as a corroded connector or dirty contacts inside a relay. This existing fault was minor and didn't cause any trouble with the old coils, and so went unnoticed and undiagnosed. It's also possible as the old coils aged, they were drawing less current than designed but as long as they fired, you'd never know.

Now throw the new coils into the equation. They put more of a load on the circuit, but still within design limits. Only now, the previously unseen fault causes the circuit to fall down, and the car won't start.

Take a look at the wiring diagrams:

JagRepair.com - Jaguar Repair Information Resource

See figure 03.4 for the V6 coils. Note the common power supply from fuse F12 under the hood, seen in figure 01.6. Make sure that fuse is fully seated with good contact.

Next, remove relay #3 (confusingly called Powertrain Control #2) from the same panel. Inspect the prongs for discoloration due to overheating, a common failure mode. Swap with a known good relay from another spot. If the fog lamps work properly, relay #7 is a good donor.

See if any of that helps. Should only take a few minutes and won't cost anything.

 

So I gets to thinking some more. Don't worry, it's just social thinking and I can stop anytime I want.

What if you duplicated the conditions that generally lead to the no-start? It's much easier to diagnose a fault when it's active. Drive for X distance, then shut off and wait the ten minutes you previously mentioned. Time things right and you could get the car to fail in the comfort of your own driveway when you have time to work on it.

Sure beats the embarrassing situation of the car not starting as you try to leave a **** shop after a picking up a special order from Sweden. (We don't judge.) On top of that, the only person available to come get you is your Mom. Then you have to have that awkward conversation where she says she's not mad at you, just disappointed.

 

 

Sorry if I missed but did you check the cam sensors? Crank sensor? Tried a seafoam treatment. Like I said I'm really sorry if it's been checked or done just tossing ideas.

 

It's already been suggested by myself, but as mentioned by someone smarter than me: why would either sensor failure coincide precisely with changing the coils? It is not an impossibility, but it is hard to find a logical link between the two. Therefore, it is less probable.

 

I would still like to know what the fuel pressure is when the 'no-start' situation occurs.

But I am enjoying some of Karl's comments.

 

Um, you're aware it's considered poor form to encourage me, right?

 

After reading the thread, here is my $0.02

Dealing with something similar on my 04 XJR. Thankfully, my situation is resolving.

First spark plugs. Should install factory plugs (NGK)

Second, have you checked fuel pressure? When you turn the ignition to run you should have north of 40 psi. Does it remain steady or drop? If the latter - it's an issue.

Third, you could be suffering from "heat soak" or a dirty/leaking fuel injector. The injector drips excess fuel into the cylinder after turn off. It will evaporate eventually but if you try and start it shortly after shutting off - it will have trouble.

Also, check the crank position sensor. Easy to pull - ensure the tip is clean and nothing on it.

Try and run some Sea Foam or Lucas' Fuel Injector cleaner. (Which is what I'm using now)

Not sure if the earlier Jaguars have it but on my 2004 when my engine fails to start twice a P1582 will set and 37 frames of all engine sensors/parameters will record. It's actually a flight recorder.

Shows RPM, battery voltage, most sensors, PATS status, even the Inertia Switch. You need IDS to retrieve the info and clear it - it's helpful. In my case everything seems to be in order.

 

I agree this would make her run poorly for a moment, but on a 6 cylinder car, it shouldn't stop it from starting. Any 6 cyl car that won't start on 5 pots has something else seriously wrong.
Even my 3 cylinder motorcycle will start on 1.

 

Any progress? Or has this become another unresolved zombie thread?

 

ok so here we go. Disconnected battery and charged for 5 days. Weather in NJ was nice and dry approx 70 degrees. Car started and drove fine. Stopped at store for approx 45min came out and car started and ran fine till I got home. Next morning weather was cold and damp approx 40 degrees F. Car cranked but no start, security LED not lit but horn beeped twice when fob lock pressed twice. car wont start at all now. Have fuel pressure but no spark.

 

Where your plugs wet? Was there a smell of fuel from the combustion chamber? How do you know the plugs were not sparking?
What I am trying to find out is if the CPS is faulty. If your plugs are not sparking AND your injectors are not opening then you might have a sensor fault. Were there any fault codes?

 

Or... does your battery hold a charge? Cold weather puts a significant strain on a weak or failing battery. Low pre-start voltage may be adequate to spin the starter, but below the minimum that the engine management system wants to see in order to make starting a "go"...

What was the voltage at the battery after last attempt to start... ?

 

See post 26 above.

 

I'm in NJ and going through the same thing with a twist... I changed my Crank sensor. Same damn thing. First start of the day - fires right up with a P1794 "gearbox fault" - battery voltage related.

Have to start my car 3/4 times for the message to go away. I'm seeing +16V at battery upon first start of the day... I'm sure the internal voltage regulator is shot.

Once car starts drives fine.

Leave car off for 20 mins, very hard to start - excessive cranking. I watch the battery voltage go below 12V (battery is new!)

Leave it off for an hour or two and it will fire right up!

I'm seeing 14 - 15.7V at battery terminals with car running, way higher than 15.1V upper end of target charging voltage.

Now I can turn everything on and the voltage will drop into the 13's...

 

Good to hear you're still here. Thought we had lost you to New Guy Syndrome.

Not trying to bust your butt, but am wondering how you determined no spark. With a tester, and you can physically see the lack of spark? Or was the diagnosis by process of elimination, such as I've got fuel pressure so it must be ignition at fault?

Same question for fuel pressure. A reading on your scanner? That's a good starting point, but not infallible. Have you physically checked with a mechanical gauge? It's easy on early models. On V6 models, the test port is located just inboard of the oil fill cap.

Battery voltage checks would be really helpful, especially when the car won't start. How about the charging system? When the engine does start, you should see approximately 13.7v. I still wonder if prestart voltage Is a factor, and if auto headlights and/or sleep mode Is part of the equation.

Is the car dead in your driveway? As frustrating as that may seem, a hard fault is much easier to diagnose compared to one that comes and goes.

Lots of possibilities in play here. Read the thread from the beginning for some suggestions. I strongly advise against throwing parts at a problem, in most cases. But in this situation, it would be quick and easy to try reinstalling the old coils on the easy side. Don't worry about not knowing which of the six old coils was bad. It will quickly show itself as a specific misfire code.

Same goes for swapping the relay powering the coils. Ten minutes tops to swap with a known-good relay, including eight minutes for a cup of coffee.

What have you you done so far for troubleshooting? Not really sure where you are in the process. The root cause may be a little too tricky to conclusively diagnose, at least in an effective manner. You may just have to try some things and see what happens.

 

Careful there! The excessive cranking is obviously not normal. The battery under 12v while cranking? That in itself isn't a fault.

For a load test on a battery, a specified amp draw is applied for X amount of time. I don't know if Jaguar has a minimum specified voltage under load, but usually a minimum of 10 volts with 100 amps draw for ten seconds is good.

We often talk about needing to see 12.6v before starting, but that's unloaded, an entirely different test.

 

Hi Karl,

Believe me I know the excessive cranking is not good. I think the alternator is toast... especially with seeing 16+Volts at the battery terminals.

Jaguar voltage range is 9V - 16V; anything outside those parameters will flag issues... I plan on pulling the new battery out and getting it load tested... this weekend

 

Hey abonano sorry to hear about your problem but yet I'm glad I'm not alone with this issue. I dont have a P1794 code but I do have a blinking DSC light. I diagnosed the no spark condition by unbolting coil pack and inserting spark plug and grounding. Saw no visable spark. Tried on 2 different cylinders. I tested fuel pressure with mechanical guage on fuel rail fitting. Pressure was fine. I dont smell excessive fuel in cylinders. Battery voltage seems fine. I load tested battery and it checked out fine. Whats confusing me is the PATS LED. It used to blink when set. Then for approx 6mos it constantly stayed on dim. Now it does'nt light or blink at all but horn beeps when FOB pressed twice. Also my car Vin ends with FM35400 so its an early 2002 not a 2002.5. and I'm having trouble finding info and diagrams. Thanks everyone for help. Ill let you know if I figure anything out.

 

And what was the fuel pressure during the 'no-start' condition? It would be helpful to know what the gauge reading was, or the pressure indicated through the PCM when the engine wouldn't start.

And what was the load placed on the battery and for how long? Was the load for ten seconds or longer?