Ladies & Gents,

I am posting the attached on behalf of a friend of mine Alistair who lives in Australia. He is a remarkable XJS owner. He is blind and a real car enthusiast, working on his own vehicles. He has bought a facelift XJR-S, an ex-Jaguar press car, travelled to the UK, and drove it at 180mph on Bruntingthorpe airfield! Yes, he is blind! (He will not be embarrassed that I have mentioned this)

Anyway, I post below his request for help. Having had the car eventually shipped to Australia, he seems to have a problem with the speed sensor or hall-effect pickup in the Zytek distributor. If anyone has any thoughts on how it could be dismantled and repaired or else replaced with an identical part from another manufacturer, he would be very grateful indeed. I will be able to direct him to read any responses on the forum here using his speech synthesiser.

Tks in advance

Paul

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I own a 1991 facelift Jaguar XJR-S litre, UK registration J95 RDU, which is an ex-Jaguar press car.

My issue is with the speed sensor in the Zytek distributor. I gather people have been able to replace the pickup by pulling apart the plastic housing containing the engine speed sensor and crank angle sensor to fix this problem and resolve this issue.

I have spoken to many people and after exhaustive research have determined that the part is no longer available or able to be obtained. The car has no other issue apart from this one.

I have determined that the coil and ignition amp are in perfect working order and have used a scope to determine that after a certain period of time and when the engine reaches a certain temp, the square signal wave form generated fails.

The car has no ecu faults, and nothing else preventing it from being back on the road except this issue.

Any assistance or advice would be so appreciated.

Thank you

Alistair

 

With the symptom described I would bet the hall sensor or connection inside the dissy is the problem.

Do you have a picture of inside the dissy of the sensors?

Also where in Australia does Alistair live?

 

I think I've heard of this component failing before, the sensor is particular to the Zytek dizzy with no spares in circulation. Phil who had the same failure was lucky enough to find a re-conditioned correct dizzy but ultimately it may be that he'll need to get the pickup part remanufactured.

Don't forget once this is resolved that ideally when refitting and setting up the timing
you'll need a timing light and the Zytek laptop/diagnostic equipment. I only know of one of these in the UK, Roddy's may have one of course with the work they do on the XJR-15.

 

XJR-Ss dizzy based on the Lucas body.
Unbranded dual pickup sensor

 

My thoughts, it is not a distributor.
Over the past three years, my friends and I too, who has Marelli and single coil ignition , we all replaced the coils.
It was a nightmare, the catalysts were melted, the engines were not working properly.

 

In the photo above that pickup and the 12 pointed crown look like the components of an optical reading system. If it is the optical gismo that has failed, it might not be too difficult to find one that will work. Luminition systems used to use such an optical triggering system, for example, and maybe they still do.
Greg

 

XJR - S Ignition
John Goodman reports that the XJR-S uses a Zytek ignition/fuel injection system -- see pages 307 and 721. “Basically
it is a modified Lucas distributor; even the rotor arm is standard. However the vacuum and mechanical advance
mechanisms have been removed (ECU-controlled vacuum sensor and programmed advance).
“It has a magnetic "Hall effect" engine speed sensor and a similar timing sensor. The 'Hall' effect thing has an inner
and outer wheel. The inner one has one notch and is the timing signal/ speed sensor, similar to the Marelli crank
sensor, the outer star like wheel has twelve notches/spikes to control injectors.
“It appears that to set the timing exactly you really need the dealer to plug in the "JaguarSport magic laptop". In the
set up screen there is a function <reference ignition timing>. This is where you set the distributor to the 10 degrees
BDC at idle for the ECU to get its base line input. After exiting the screen the ignition timing reverts to the control
of the ECU.
“So, under the ECU control, at idle you should be seeing 3.5 degrees and at 3000 rpm it should be around 18 degrees
if the timing is right. It is a damn inconvenience not being able to check or set the ignition timing without the software.”
The Zytek system continued to use the altered Lucas distributor even when the baseline XJ-S was fitted with the
Marelli ignition.

From Kirby Palm

 

I'm looking for XJR-s circuit diagram of engine management.

 

I turned this up just now. It does not say what the system is for the 12 tooth thingy, but it does say that is what does the injector signal to the ECU. There is apparently another sensor in the Dizzy that does the spark timing.
http://84.22.143.158/files/%D0%A0%D1...JRS%201992.pdf

and right at the end of this document is quite a bit of XJRS stuff that might be useful
http://www.jagrepair.com/images/Trai...20-%202000.pdf


Greg

 

The document states the XJR-S has sequential fuel injection. This makes sense as the sensor in the picture has 2 pickups, and if you look carefully the reluctor wheel has an inner flange with 1 hole in it. This is TDC 1A for timing of the sequential injection.

The manual also lists the sensor as a Hall effect unit. If you can carefully get the sensor body apart, you may need to cut it open, the Hall effect IC can be replaced.

Alternatively you could look at making a new sensor. The orientation of the TDC sensor is critical and can not be relocated in the dissy, the engine speed sensor the one on the 12 tooth part of the wheel is not critical as long as it lines up with the teeth the same as it was in its original location.

You could make something like this

 

Gents,

Thank you all for your inputs so far. I'm trying to get them all fed back to Alistair.

Warren, he is based in Sydney.

Please do keep any further thoughts coming, especially any idea on how that hall-effect reluctor could be mended / replaced. As Alisatir has mentioned, he believes that it is breaking down under heat and seems to be some sort of resin-encapsulated item.

Tks again,

Paul

 

Breaking down under heat is a classic sign of bad solder connections. If it is resin encapsulated then it's not repairable I have tried before and by the time you chip away the resin the electronics are shot.

That pic I posted is an OEM Mitsubishi unit from the Australian Magna.

He could use 2 of these to make a new one (would just need to check specs and vane dimensions), it would require fabrication of a mounting arrangement.

SR16C-N | Digital Hall Effect Sensor, 50 mA, 3.8 ? 30 V dc | Honeywell

 

Looking at the specs this would be a better vane sensor

4AV13A / 4AV17F | Digital Hall Effect Sensor, 50 mA, 4.5 ? 26.5 V dc | Honeywell

 

Al here...!

Sorry for the delay in replying - have been away over the Christmas and New Year break with no internet connection.

I have found that GM have a very similar Hall-Effect sensor to the one used within the Zytek distributor. This sensor was used as the crank angle sensor for the Buick V6 engine that was fitted to the Australian Holden Commodore between 1988 and the late 1990s.

I have purchased this sensor, and as you can see from the photos, the part of the sensor that the toothed wheels ride within looks very similar to the original sensor. Hopefully, by (carefully!) cutting off the excess plastic, and constructing a new mount, we can get this sensor to work.

The only issue that I can foresee is that as the GM sensor has a wiring plug built into it, there may not be enough space inside the distributor to mount the new sensor, even after all of the excess plastic is removed.

We may have to find a way to remove the plug, and solder some wires to the sensor directly.

We haven't taken the distributor on my car apart yet, so we also don't yet know if the spacing between the sensor elements is the same as the old sensor - but it is probably the best chance that we have!

Thank you everyone for your responses and feedback so far. I will update this thread with new developments as they occur!

 

Hi Al how did you go with this mod as we are in perth and have the same problem with a XJRS and was looking to do the same thing
regards Darren

 

Dear Everyone,

Apologies for taking so long to respond, but I was unable to access this forum for a long time due to technical difficulties with my PC.

I have resolved the issue back in January, as you will see from the following photos.

Darren - if you would like some help, email me your details (alistairjclee@gmail.com) and I will contact you with all the information.

As you can see from these pictures, the Zytek system should not be feared, however care does need to be taken to avoid the replacement sensors contacting the sensor wheel. If this was to occur, the sensor wheel could be irreparably damaged. As these are no longer made, it would be impossible to replace.

Since January, I undertook a 1,500 mile trip in temperatures nearing 40 degrees Celsius with no trouble at all!