I have a 1998 Jaguar XJ8 V8 that occasionally won't start.

The problem is intermittent--most of the time it starts fine. But every so often I turn the key and... nothing. Doesn't even turn over. I switch the ignition all the way off, then back on, and it is 50/50. After a couple tries, it always has started, but I'm worried about getting stranded if this problem gets worse suddenly.

In case it's relevant, I recently had the switch replaced that controls whether the car senses it is in "park". That fixed a problem where the car would crank but not start when it park (it started fine in neutral). Since that, the car has not had any problems once it starts to turn over--it always starts in that case.

Any help and advice would be appreciated.

 

I've had an issue with the same symptoms. I don't know if the problem was the same as yours but alas. I found when there's no crank it's usually because the key was turned too fast. If you have this issue then:
Turn the key all of the way back to the off position. You may even have to take the key out of the ignition and put it back in
Turn the key to the on position (the odometer area will say something along the lines of [system diagnostic]) and wait for the lights on your dash to go away
Then you can begin cranking the engine and starting it.

My theory is that it just takes a second for the ecu to boot up before it will let you start cranking.

 

I suppose I should add: for me, the problem seemed to be more frequent in the winter months. So I suppose it could be a battery issue, but I've had my battery tested. However, once I started turning the key a bit slower, I never dealt with the issue again.

 

check the fake firewall ground

 

I get a hesitant crank when I turn the key over really fast(usually in a rush) I take it the ignition collar needs adjustment or similar. Happens maybe 3x per year.

 

Sorry, can you elaborate, or provide a link? What's the "fake firewall ground"?

 

I definitely agree it seems to happen when I'm in a rush, but sometimes I stop, go slow, and it still happens... I think. I'll have to experiment a bit. It is summer here now, so definitely not a cold things, and the battery seems very strong--turns over healthily.

 

My 2002 XJVP does the same thing, but I have no insight into the cause or solution. Thinking it might be a battery issue, I connected a charger to it and tried it again later in the day. It started with no problem. Its happened a couple of times before over the years, but haven't a clue as to the cause. I'm guessing it has to do with the switch or wiring connections to it, rather than the battery. I have AAA, so I roll the dice.

 

left side of engine bay facing the back

has a rubber cover on it

 

i've got same problem, after hanging it to comprehensive scanner (not all codes show up on ordinary obd) i found code similar to "anti theft control triggered" (don't remember exactly)
so it looks like car thinks i'm stealing it and won't allow crank, usually key removal and reinserting does the trick but sometimes i have to lock/unlock the car to get it back
Perhaps something is loose somewhere but i won't dig it for now.

 

Reset the immobilizer: look for it in the Drivers Handbook

 

The DTC P1260 is the 'code' for KEY NOT RECOGNIZED and I see it in a bunch of cars when diagnosing.

Sometimes I think the key gets 'turned' too quickly for the RFID and KTM to communicate and it just flags the code.
Another try at the key and the engine starts so people don't even think about the failed first starter attempt?

You might have more of an issue if you see the P1260 very often or almost every attempt at starting.
The ECM and Body Control Module are involved with starting the engine. Also check the power stud on the 'false-bulkhead' to the starter/alternator wire?

 

worth checking, bloody power stood left me stranded on the beach for half of the day, luckily, after long fight and just when i gave up and was about to tow car back home, my personal angel appeared out of nowhere and fixed that for me in no time
Thank you God and the out of nowhere guy, you saved my holidays!!!
Checked codes again, in my case it is P1260 Theft Detected, Vehicle Immobilized, it is more frequent in hot, so i suspect something expands to much maybe connector maybe module pcb, symptoms are the same as above and car starts eventually