Hi everyone.I am a new member today but I have had my XJS convertible for four years.I bought it on Ebay in California.I had an almost identical XJS convertible way back in 1991.Red with beige leather.This current car is Red with black leather.Black leather is infinately more suitable for an old car enthusiast .I was lucky to find this one owner low mileage [30.000] car in excellent condition.As I live in France now I have had to get it through type approval.Not something that I would care to repeat.I won't bore you with the two years of misery dealing with french officialdom.I have a couple of issues outstanding with the car and I am sure that someone will have all the answers.I collected the car off the boat in Le Havre,and after 120 Kms the speedo packed up.I eventually realised that there was no cable involved and that it is electronic.How do I locate the problem part ? There is a sender on the diff,a wire between,and the speedo "head".I find the proper factory workshop manual very difficult to follow.The second problem is bleeding the brakes.Today I tried to do it exactly as explained in the manual but with no sucess at all.The car is 1991 and to californian specification in most respects.I intend to try tomorrow with my ezibleed with the ignition on.Trying today to bleed the rear calipers with the nipples only 3/4 of an inch away from a hot exhaust pipe was most unpleasant,especially with the engine running and the gearbox in neutral as demanded by the manual.Any help would be gratefully received,john.

 

Welcome to the forum John,

I've copied this from your Intro.

Members with the same model will be able to help with information on the speedometer and brake bleeding.

Graham

 

Not sure what to tell you about the speedo, but I just finished a complete brake system flush after putting on new calipers, and all new rubber lines. I even took the reservoir off and cleaned it out as good as possible. I will tell you that the car does not have to be running at to bleed it properly, but it does take two people. I did the front two first using the old fashioned way. Get the help to pump the brakes, and keeping pressure on the pedal, open the bleeder nipples and allow fluid to run free. When your helper tells you that the pedal has reached the floor, shut the bleed nipple and repeat. Repeat as often as it takes to know that you have clean clear fluid. I should also add that I used a piece of clear vinyl tubing so that the fluid wouldn't go all over the calipers.

Moving to the rear, get your help to put pressure on the brake pedal, and then turn the switch to "ON" but don't start the car. The ABS pump will push fluid as long as you feel the need for it to. The pedal may not go to the floor. Do both rear calipers, the same way. Check your fluid lever often, but once you are sure you have all the old fluid purged, and the reservoir topped up, just turn the key on and wait for the accumulator pump to stop running, and you will have all the brake pedal you are going to get. Good luck!!

 

Re brakes: I have no recent direct experience, but I believe you should not run the pump for more than 15 seconds at a time when bleeding the back brakes, and give it a minute to cool down between pumps. It can burn out otherwise.

Re speedo: If you have the diff mounted sensor, which you I think say you do, then there is a module in the boot somewhere that the signal goes to before going on to the speedo head. This can either pack up, or poor connections stop the signal. Try finding it and cleaning the connections, any earths etc.

Greg

 

Thanks Greg,Where are you in France,I am at 86430.cheers John

 

The brakes are sorted but does anyone know how to sort out a non working electronic speedo ? How do you isolate the problem ?

 

The system is as follows:
The diff sensor sends a signal to an electronic unit in the boot, LHS. From here the signal goes to the dash unit, and from that to the speedo head itself.

One or more of these items is not working. The sensor may need a clean on its reading face. It bolts into the diff back with a small bolt. Undo it and the sensor pulls out, there are shims to ensure the correct distance of the head from the crownwheel teeth, which it 'reads'. The boot unit can be unplugged and the connectors cleaned. If this does nothing you are left with:

1 Duff sensor, 2 duff wiring somewhere, 3 duff boot unit, 4 duff multiplug connection into the dash unit, 5 duff dash unit flexible circuit connection, 6 duff speedo head.

My favourites are 3, 4 5. Just a case of working methodically through it. Someone else will know for sure, but if you jack up the car securely and run the engine and back wheels, I suspect you can test with a meter the boot unit output signal. Post again when you try the first things if no joy

Greg

 

One possible clue on the speedometer problem.....

The trip computer uses the same sensor readings as the speedometer. If the mileage/distance functions of the trip computer are working normally then it's a fair bet that your speed sensor in the diff is OK.

Cheers
DD

 

Following on from Doug's comment, if the trip computer is reading ok, then the speed interface module in the boot is also working ok. If this is the case, then the fault lies in the speedo or instrument panel wiring connection.

The shims in the diff sensor are critical. Even one shim too many or too little can cause the speedo to malfunction. However, if nothing has been disturbed in the diff then the shims won't be the issue.

Good luck

Paul

 

I was about to say the same thing but from the diagrams it appears that the interface unit has separate outputs for the speedo and the trip computer....leaving the possibility, even if only slight, that the output for the T/C is OK while the output for the speedo is on the blink.

Cheers
DD

 

Thanks guys I really appreciate that.I will start with the boot.If the axle has not been disturbed then it should still be shimmed ok.It dosen't wear does it ? Does anyone here want to buy a genuine "D" type crank/rods and pistons? Fitted and running as a 3.8.