The car is a RHD 1997 X300 Sovereign 4.0 automatic and, having left it parked at my girlfriend's house for a few days, it refuses to turn over.
Turn on the ignition and all the dashboard lights come on as usual, but when the key is moved to the 'start' position absolutely nothing happens - not even the click of a relay is heard !
My first thought was that the battery had thrown the towel in, so charged it for 24 hours and still the same.
Now I see that about half the electrical system is not functioning, and half is still fine.
What is completely non-working are: starter, side lights, headlamps, fog lamps, direction indicators, hazard flashers, screen wipers, screen wash, and the gearchange inter-lock. No relay sound is heard when the brake pedal is pressed.
Working fine are: Interior fan, radio, window lifts, sun roof, horn, defrost blower, mirrors, door locks, engine cooling fan, dashboard lights, boot release, steering adjustment, seat adjustment, brake lights.
It strikes me that perhaps some major connection in the electrical system has come asunder or a major fuse has blown or circuit breaker tripped but I'm unsure of where and what to look at next.
Any help towards tracing this problem will be gratefully received as I am stranded without much of a toolkit or workshop manual.
Thanks in advance,
Kevin.

 

I think most of these are "cranks but won't start" but there may be something useful in there. At least til Doug, Don, Ross or others happen along to offer insight:


https://www.jaguarforums.com/forum/x...ngines-120221/

 

[QUOTE=aholbro1;1052147]I think most of these are "cranks but won't start" but there may be something useful in there. At least til Doug, Don, Ross or others happen along to offer insight:

Yes, thanks aholbro1, I did check other threads first before posting this problem but there was nothing else showing the particular electrical problems my car is sufferring from. I am guessing that this particular unique combination of what works and what doesn't work will indicate some kind of break in the supply of current from the battery into a bunch of all the systems which are not functioning. Possibly something like a blown fuse or tripped circuit breaker ? While, of course, those circuits which are still functioning will be supplied via a different route.
What does rather concern me is that vital safety circuits, such as the hazard flashers, have stopped working while relatively trivial circuits like the radio continue to function ! Oddly, the only lights which function are the brake lights. If this problem had occurred at night on a busy road it could have lead to an extremely dangerous situation.
Hopefully, somebody will recognise these symptoms as indicating a specific fault that I am able to fix. Hopefully . . . . . . .

 

My first thought with this list of symptoms would be the BPM (Body Processor Module). It's a pretty key component in the car and has a role to play in many things. Problem is it often only fails in part so some of it's circuits continue to work while others don't so there isn't a definitive list of how to to identify a failure.

I would start there and do some checks on inputs and outputs. You can download the electrical diagrams from the sticky "How To" thread.

I would normally discourage random part swapping but if you don't have the tools or knowledge to do that then you could could just get hold of a second hand one (about 15-20 pounds on ebay) and see.

 

Thanks, b1mcp, when I get home (when ? eventually ?) I'll see about getting a spare BPM and make sure it is fully working. I'm guessing it is just a selection of basic electronic components arranged to give some logic to various functions ?

Meanwhile, I continue to be stranded at my girlfriend's with a non-starting car and the need to drive home today - so I desperately need a quick/emergency 'fix'.

I continue to be rather worried that the side lights and hazard flashers have been rendered inoperative by this fault, as I would expect there to be no circumstances under which one might logically not wish these to operate. Therefore I would expect them to be wired to the battery simply via a switch and fuse for reliability. In the long term. I'll be looking to solve that problem with a permanent modification.

But, for now, I just need to get my car going !

 

Well, I managed to get the car to start at my girfriends and drove halfway home to my parents house, where it refused to turn over again and is now, once again, stranded !

After having it on charge all night, I attempted to start it with the charger still connected and no problem. Then a 40-mile run to my parents, half-hour stop, and it wouldn't turn over again.

Got advice over the phone from an expert who declared that I needed a new battery, so took the old one round to the shop but the guy said he unfortunately couldn't sell me a battery as mine was performing perfectly. He blew up one tester then nearly melted another tying to discharge it with a soak test, and said it was better than most new ones.
So it seems the car will turn over when it is being 'boosted' by the battery charger, but not just from its own battery. This strikes me as a small voltage drop somewhere, which the boost from the charger is managing to overcome. Perhaps this is due to a bad earth or maybe a bad connection in some circuitry somewhere ?

Does anybody know if there is some voltage detection circuity, perhaps in the elusive 'body processing module', which is intentionally inhibiting the car from starting because it (wrongly) thinks there isn't sufficient voltage in the system ?

It looks like I now have to start searching around for bad earths and suchlike, so, would anybody like to suggest the most likely places to begin looking please ?

Many thanks in advance,
Kevin.

 

Sounds like he's clueless about what he's doing. The girl at NAPA kept insisting my XJS battery was good till an old timer behind the counter convinced her to put a clamp on spot light on it and she watched it sail down to 7 wolfs (not enough to start a Jaguar). Batteries will hold a fine top charge (12+V) but not hold it under load are bad batteries and some places only check it static. If he's blowing stuff up and melting stuff he's clueless as to what he's doing. I'd go somewhere else.

 

Hi Kevin,

Sorry to hear about the trouble you're having. The fact that some circuits were functioning and others weren't implies an intermittent connection somewhere, but I also tend to agree with JTsmks that the battery is a primary suspect and is probably contributing to your issues. If its voltage sags much below 12V while cranking, the Engine Control Module (ECM) will not trigger the ignition to fire. From your description of the tests that were done on the battery by the "expert," we're skeptical that he properly tested it under load.


The voltage drop may be in the battery itself, or it could be due to, or exacerbated by, corrosion or looseness in an earth/ground or a poor connection somewhere. You might start by ensuring the battery cable terminals are sparkling clean and the point where the negative battery cable attaches to the body is free of corrosion and snug, as well as the connections for the 500A megafuse in the battery positive cable. There is a 250A megafuse under the right rear seat that feeds all the fuseboxes except the one in the boot/trunk. Another common problem is corrosion or looseness on one or more of the three large battery power studs on the bulkhead/firewall, which feed various critical circuits.

If you don't have any luck downloading the Electrical Guide from the X300 'HOW TO' quick links near the top of the home page of this X300 forum, send me your email address in a private message and I'll forward the manual to you in pdf form. I think a little time comparing your list of non-functioning circuits with the schematics may lead you to a common point where you are likely to find your problem (and may confirm Brendan's suspicions about your BPM).

Please keep us informed.

Cheers,

Don

 

Thanks for the ideas guys.
I think the guy in the shop who would have sold me a new battery if I needed one was managing to over-heat his testing equipment because the battery voltage just couldn't be made to drop under load - so he left the test rig on it too long ! Anyhow, the battery was able to spin the engine over very quick when the car was behaving itself so I've no inclination to buy a new one just yet.
I found the dreaded BPM, took it off the car, and took it apart. The circuit board seemed to have white powdery deposits all over it so I gave it a good clean and put it back. The earth stud it uses looked okay to me, but I managed to give the nut on it a quarter-turn tighter just for good measure.
The car now merrily spins on the starter but I don;t know what fixed it ! Perhaps just a slightly diry connection ?
The latest fun is that the car will now sometimes fire as soon as the engine is turned by the starter, and sometimes takes a moment of spinning before it chooses to fire up. Any ideas on this one ? This problem seems to be independent of engine temperature. Spark plugs are quite recent and ignition connections look sound.
Generally, for a 1997 car, everything seems remarkably clean and corrosion-free. Every electrical connection I have seen so far looks bright and shiny.
Thanks guys.

 

Failed camshaft position sensor reportedly culminates in up to 30 seconds of cranking until the ECU decides what's what.

 

Thanks, aholbro1, that sounds like something potentially worth pursuing. It sometimes takes a bit of cranking and sometimes fires up nice'n'quick.

My understanding is that the crank position sensor is responsible for determining the timing of the sparks (well, it gives a reference at least) while the cam sensor will give a clue as to which of the six cylinders should be firing at any time - is this correct ? I've heard that, given insufficient info from the cam sensor, the ignition computer will 'hunt' around trying to find a cylinder which will fire and then all is well - hence the variable delay. Have I got this right ?

Anyway, the big question is how do I test the cam sensor without forking out a pocketful of dosh for a new one ? Is there, perhaps, some kind of diagnostic procedure I could follow or maybe some way it can be cleaned, serviced, adjusted, or checked, etc ?

Thanks again guys.

 

The best way to test the CAM position sensor is with a Scope. It's a tool that surprisingly not many people have. For basic measurements you can buy decent chinese USB scope for around 50 -60 pounds on ebay and hook up to a laptop. Or you can buy a Picoscope kit for about 1,200 pounds !!!!

If you fancy a trip down the M60 to Urmston then I can test it for you.

 

b1mcp Could it be that you have a tie with mcp and images of a certain farm animal? I was presented with one by a friend of my wife many years ago. You appear to be located in Manchester - I am in Chester.

 

No that's not me at all, and I'll get the wife from the kitchen to prove it if you want.

The b1mcp is simple. It's my personal registration and is from my initials
Brendan MCPhillips.