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XJR-S Engine Pictures

Engine Pictures


General view of the engine, not much different from the standard V12 with special cam cover badges! see my car

Closer examination reveal the two injector power resistor packs and additional air temp sensor. Note also the special ram air intake funnels built into the radiator top rail (this JaguarSport part is still available and the air boxes), the later cars had a rubber boot connecting the trumpet on to the air cleaners to the intake funnels.


Single small high performance ignition coil, part no DAC 6093 this can be used successfully to replace the twin Lucas coils on the HE.


I still do not know what the difference is on this sump compared to the standard sump, can only assume it is something to do with the baffle ring. Some of the standard V12 cars suffered from strange oil surge problems while brakeing and cornering to the right. This is a photocopy from the XJR-S parts manual.

Internal distributor pictures will be included shortly.

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Zytek ECU's

For a real technical insight to this system get the XJR-S Product Support Manual from Chad Boles or try your dealer.

I don't have the "Check Engine" light on my car, or the error codes flashed to the trip computer display facility (less to get paranoid about!) this only came out for the '92 cars and is the most irritating thing. This light is known to come on for no apparent reason, it will also stay on if any sensor or connector is disconnected, (even if it is connected back up straight away) while the ignition is on, or started with anything disconnected necessitating a trip to the dealer to reset it! However, provided everything is in order and you haven't left anything disconnected, it can be reset after 50 start stop cycles and not just 50 ignition on/off cycles as previously thought. Many thanks to Emile Desroches for confirming this and subjecting his car to the torturous experiment.

Unfortunately, in my experience, the average Jaguar dealer does not know much about the Zytek injection system on these cars, if they cannot find an obvious fault they will try to blame the Zytek computer or distributor pick up, which is actually quite robust and the distributor not as complicated as the Marelli system. The dealers had special telephone support hotline to JaguarSport for all technical problems with XJR's and XJR-S's. However, when the JaguarSport partnership dissolved all the knowledgeable technicians moved on to other projects so the dealers cannot get this specialist help anymore.

I have received recent information that after JaguarSport, some of the XJR-S engineers, while still with TWR did a lot of the developement work on the DB7 for Aston Martin. At least one is responsible for the design of the electronics on the wonderful XK 180.

I had the impression Zytek won't give away their software or the special interface cable which is necessary to program the ECU (a dos based program) because of some Jaguar copyright. To be honest they don't want to know about JaguarSport owners problems other than their willingness to bench test /repair their ECU's. Remember also it is late '80's technology and only one or two people there can remember what it's all about! To be fair their current systems are "cutting edge" and used by leading race teams. A Zytek system was used on the Euro versions of the AML DB7, but unfortunately the "bean counters" had to change to the Ford EECV for the worlwide car (economic ,not an engineering decision). Zytek went on and further developed a OBD11 system for the Rolls Royce (which Ford didn't think could be done, so was a glorious two finger salute to uncle Henry when the car was launched!)

Zytek Systems, London Road, Bassetts Pole, Sutton Coldfield, West Midlands, England,. B75 5SA

tel:+44 (0)121 3232323

I received this from an ex Jaguarsport engine managment Engineer:

>>It is difficult to do any work on a Zytek car when you haven't got the interface unit, and then there's the software to suit the different levels of EMS release (different levels of emissions, diagnostics, etc.).......and of course, the relevant dealer manual to tell you how to get the whole thing running!

Unfortunately, the Zytek link lead incorporates a unique electronic interface box, so it's not just a case of making up some cables (unfortunately). It's not something peculiar to Zytek - all the Lucas systems (and Bosch) were the same at that time too - something to do with the pc's.

The Interface Box is a unique piece of Zytek equipment. Parts were: Laptop to Interface cable- SPD1040 Interface Box - SPD1039 Interface to ECU cable - SPD1038. For 'tweaking' the tune you need a lot more than the dealer service manual. You need the development aid program, and I'm not sure where all that stuff went. I'll make some enquiries if I get the chance. (anon. TWR/ Jaguar)<<

It taken me over a year to find the intermittent ignition fault on my very low mileage '89 XJR-S. The frustrated Jaguar main dealer brought two technicians down from Zytek who had even better equipment and still could not isolate the fault, even though it was playing up at the time. To cut a long story short, Jaguar transported the car back to the factory to investigate, after three weeks they could only find one connector to replace (I had already changed and cleaned all possible connectors, and replaced nearly everything else except the very expensive ECU) needless to say I was not impressed! I found the fault myself eventually..... a dry solder joint inside the bound up wiring harness from the ECU to ignition power amplifier. Obviously faulty from the factory, I had a complete new engine harness from Jaguar free of charge after a big fuss. Wiring connectors and poor earths account for most problems, it may be worthwhile cutting open the harness to check the conditon of wires, particulary the braided earth shield from the ignition amplifier back to the ECU.

I found Ms. Debbie Colchester (Consumer Affairs Manager) at Jaguar customer services quite helpful in trying to find technical information for my dealer to work with, apparently a lot of JaguarSport data faded away when the company disbanded, with Jaguar Cars were left holding the baby when TWR moved on!

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