I bought this XK8 as a non runner which, according to the seller, it had been until parked for 2 weeks. I tend to discount what a seller says as they may just want to get rid of a problem car!
Anyway, symptoms are; no ignition, gear shift inhibitor doesn't release when brake pedal is depressed, fuel pump doesn't run when key turned, list of 'faults' displayed are Engine fault , gearbox fault, incorrect part fitted. and an 'err' message is displayed on A/C display. Now, a really weird one... Sometimes the window switches swap over! ie passenger switch operates driver's window and vice versa. The windows go up and down when this happens but you can't set the top and bottom positions ie no click from the door modules. Turning the igngition off and back on returns the switches to the right windows!!!!

 

No. 1 suspect is the battery.
Closely followed by the battery
Then connections to the battery

 

Failing that, try the battery.

 

Hi, thanks, I had already checked it! It has a new battery, fully charged. I fitted the ems relay into my xjr and it works fine. I then did some comparison readings with my 2001 xjr around the ems relay and fusebox. I have found small resistance on the ems relay earth socket whereas there is full earth on the corresponding relay socket on the xjr. This is the relay that brings the system to life and switches power to the fuel pump amongst other things. It's getting too dark here to continue. Tomorrow I will trace the earth which feeds the ems fusebox.....wherever that might be, hidden from sight no doubt!

 

I'm dealing with a similar problem on my 2001 XK8. I'm currently looking into my ECM. AutoECU says there's corrupted software, so I just ordered British Diagnostic SDD v 130, No shop wants me to have it towed in, because they don't want to take in dead cars. Actually, I did take it to a shop that replaced the fuel pump, which I questioned, and wrong since it was nevrer a pump problem. My symptom is the car will start and run, but when the key is turned off, the engine keeps running. When killed by disconnecting the battery, it won't restart for a day. All relays are good. Battery is good.

 

When it won't start, I have no fuel pressure but it cranks.

 

You should probably start another thread, as your problem is nothing like the original problem, and let us know more details: When the engine runs on, does the dash stay turned on, how are you measuring fuel pressure,etc.

 

I had time to do some tracing and the EMS relay is operated by a switched earth, or rather mine isn't . If I put an earth on pin 5 of the relay it operates, fuel pumps runs, ignition relay operates but drops out after a few seconds so no time to run round to the driver's side to see if it turns over. I am suspecting everything as a possible cause but will start from the very begining ie when the key is turned in the ignition to the second position. I have the xk8 workshop manual disc with all the xk8 wiring diagrams but , annoyingly, they don't show every connection in an individual circuit on the same page so you follow a wire to the edge of the page, and the next page doesn't pick up where the last one left off! you really need a full size layout to trace connections all the way through but I will do it the hard, and slow, way with my trusty Fluke meter.

 

Is the new non-runner a '98 as per your sig?

 

Hi, no, it's 1997 I sold the '98 after fixing it's similar no-starting problem and was hoping this one had the same fault. Being a jaguar it of course wasn't the same cause!
I have just spent a couple of hours going over the wiring diagrams and I am now looking at the key barrel' as this is where the ignition switched earth originates, as far as I can see this is initiated when the key is turned to the second position and the earth is sent to one of the pins on the EMS relays which operates and passes 12v through to the rest of the engine management components. I had some time earlier this afternoon to go outside and do some wire tracing, then it rained heavily...as it always does.
Regards

 

Hi,
Can you confirm which relay is missing its switched ground: - is it this one in the Engine Management fusebox?:

 

HI, yes it's that one, I put an earth on it and it operates, but if I unplug the starter relay (which isn't operated) the EMS relay stops running??? weird or what!

 

Hi,
In a normal situation, the ECM controls the EMS control relay, and for whatever reason, the ECM is not doing so here and the engine management systems remain shut down.

I would check for codes:- there may be an issue with the security system e.g. the key not being recognised. Do you have another key you can try?

Check also that the inertia switch hasn't tripped. It's in the passenger side (RHD) fascia fusebox. See frankc's post here:
https://www.jaguarforums.com/forum/x...1/#post2128787

The starter relay is fired by the BPM, but there's a feed back to the ECM which might detect that the relay has been removed (12V via relay coil missing).

 

Hi, I already checked for codes and there are none. I thought I was getting somewhere when I stripped the top of the shift selector ( since I bought the car a few weeks ago I hear the beeping you get if you move the lever out of park when the key isn't turned ) so to take my mind of the main problem I thought I would fix this one. On removing the top section I saw that the little sprung contacts that operate the micro-switches were both broken off and lying at the bottom of the assembly.
Luckily I had a shift assembly from an XJ8 which fits, apart from one fixing bracket which isn't quite long enough to reach the existing captive bolt but it's held tight by the other 3 that line up. Interestingly both units have exactly the the same part code? Anyway, it cured the shift issue but, of course, not the main one! I tried a BPM from an XJ8 but that caused more problems than it solved ( m car is a convertible and the xj8 BPM caused the hood pump to run constantly, and the car still didn't crank anyway. I'm begining to wonder if the BPM is the culprit. Somewhere in my garage boxes of spares from various jags I'm sure I kept the BPM from an XK8 coupe I broke for parts a few years ago....if I can find it.
I'm reaching the stage where I think I will go back to square one and start tracing the fault again, ignoring everything I have already done, just in case I missed something crucial the first time!!