[Roadhogg]

Hi to all,
I have a 2000 XK8 which has been sitting on my dad's drive for at least 6 years, while during visits to him, I have replaced the gearbox oil pipes without dropping the gearbox out. This entailed removing the exhausts up to the manifold, throttle body, header tank and heater control valve with octopus pipes to get access.

While putting it back together, I have noticed strange behaviour in the instrument cluster, namely the instrument lights not working (except sometimes when they are not supposed to be on).

Also, with the battery connected, the minor cluster warning lights for oil pressure and battery voltage come on, and stay on, even with the key out of the ignition, the car locked from the outside and the alarm set. On one occasion under those circumstances, the instrument lights came on sometime later, and stayed on too, so I had to disconnect the battery to avoid possibly draining it flat overnight.
Just to add to my problems, occasionally, when reconnecting the battery, I get a fast clicking noise from the rev counter and speedo, as they bounce up and down slightly from their at rest states.

I have pulled every fuse and relay from all 5 fuse boxes, but no fuses are blown and no relays seem improperly connected or dirty, and show no signs of burning at the contacts.
I know relays can pack up without any outward signs of malfunction, but the instrument lights do work, although only when they shouldn't, but not when they should.
Last week I got the car started, but the rev counter showed no reading at all. The car is still up on plastic ramps so is not ready to move yet, but the speedo probably won't work either.
I know there are 3 ignition relays and an engine management relay, plus a body control module, so my questions are, has anyone had similar behaviour from their instruments and found the cure, or could anyone suggest what the cause could be?

Could it be anything to do with this thing in the pic? The black box centre of pic just in front of the rear engine bulkhead. I don't know what it is called, or what it does. Is it the ECU?

 

[Roadhogg]

Just to update,
I unbolted the black box in the above pic, carefully removed it from it's holding bracket and (also carefully) prised open the 3 clips on the far side of the box. Those 2 black hoses going in to it contain big bunches of wires, and on seeing that, I just closed it up again and remounted it in it's bracket. I am not good at mechanics, and am especially bad at electrics, so the only way I would investigate that bit again is if the car won't move out of park when started.

I did test all 3 ignition relays with the known good fog light relay, but it made no difference to the situation.
In the absence of other ideas that were fairly easy to try, I then pulled the instrument cluster fuse at F18 in the drivers side fascia box. As expected, no instrument lights still, but the mini cluster warning lights started working as they should, coming on with ignition on, and going off with ignition off. That was strange, because if they are controlled by the instrument cluster fuse, they shouldn't come on at all, and if they are on a separate fuse, pulling the main instrument cluster fuse should make no difference to their previous permanently on state.

if it's a faulty body processor module, I don't want to go in to that if it's behind the passenger dash, and an airbag, and I won't be buying a replacement BPM either.
I don't think the instrument cluster Illumination light problem will be solved, unless by chance, as the car will only be sold for spares anyway.
The only other problem is that after starting it 4 times the day I first got it running, the following day it wouldn't even crank, which is probably loose or corroded wires to or from the starter motor, or a faulty solenoid or starter relay.
My dad will be so happy to finally get it off his front drive.
Thanks for reading

 

[ducmon]

Hi,
I presume you have checked the battery.
Do you have a scan tool. You would need something that can read all the codes.

I would use an icarsoft i930.

As it is pure guess work at the moment.

 

[Roadhogg]

Hi ducmon,

It's not the battery, it's well charged and the terminals are good and solid.

I moved on to removing the rear joints to the centre exhaust section after I initially got it started, and I wondered if wiggling the sections that go over the rear axle may have damaged the battery leads under the car, but those exhaust sections just scrape the heat shields, and I couldn't find any cable damage.

I have thought of getting diagnostic software in the past that can read all codes, but since the car is going to be sold for spares, It's not really worth it at this stage. i just wanted the car running so it could be driven on to whichever recovery truck collects it for the buyer.
It's a bit galling that after standing on ramps for at least six years with various bits missing from the engine, I put it back together, get it started several times, but am now getting a failure to crank.
It's also stuck in park at the moment. Hopefully if it starts again I will be able to change gear lol.

I looked in the manual at replacing the starter motor, but it says to remove the steering rack for access.
That seems like another fairly involved job I would much prefer not to have to do, unless maybe I can drop it a bit wouthout disconnecting it completely (ie: removing ball joints etc.)

I still have two things to do before knowing the starter motor is the fault.

The first is to clean and test the quality of the contacts to the starter motor and leads. I had some trouble being certain of where the starter motor was initially, as it's described as being at the left rear of the engine. Having to remove the rack for access suggests it's directly below the oil dipstick.
After that, the second test is with a piece of wire in the starter relay as described by a lady named Beatrice on youTube.

I have come home from where the car is for now, but will get some wire and some de-ionised water to clean the gunk off the starter contacts, and go back to the car next week.

Thank you for your suggestions, and I will update this thread as I continue to test for the problem.

 

[Roadhogg]

Apologies to beatrix for the name error.