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XJS CUTS OUT

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RODNEY

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Hi all ,I have a 1977 XJS V12 which I bought to restore, engine fine but it cuts out like it's out of fuel but it's not you can be cruising along come to a trafic light i.e and it cuts out and you turn here over and it sounds as if there is no spark or firing at all you wait a little while and she will start? any Ideas
Regards Rodney
 
You have a fault in your ignition system. It is either your ignition amplifier or your ignition coil that has a heat sensitive glitch. (odds are it is the ignition amplifier). Replace it and the fault should go away. There is a small chance that it could be in your distributor cap if the fault persists.
 
Welcome to the forum Rodney! I think you may be our first member from Spain! (Does the rain their really fall mainly on the plain?) Just kidding, welcome aboard!

Basil
 
Rodney, You have an early model ignition system which mounts the ignition amplifier in the space between the heads and near the distributor. This creates a real hot box for the electronic amplifier which subsequently fries it. That has got to be your trouble. When you replace the amplifier, I would recommend moving its mounting position from the original position to somewhere where it can get some cooling air like the sides of the engine compartment or the radiator mounting brace in front. I just came back from a trip to Central America and my Spanish is better than ususal. De donde estado esta usted de Espana? Hasta luego y bueno suerte, Jack
 
Hello Basil , thanks for welcoming me aboard I am pleased to be a member and thanks for letting me join. Regards Rodney from Spain
 
Hello John , thanks alot for your help ,is there any way to test these amplifiers? and I suppose they coil just change over when fails yes?
I live in Vigo -Pontevedra which is in the north just over the top of Portugal so Buenos Dias Amigos
Regards Rodney
 
The best way to test them is to substitute a known good one. Your early mdel is rebuildable. If you open up the black box, you will find a common General Motors amplifier used on HEI ignition systems of the seventies. There is also a power diode and a capacitor. The GM component is usually the failure since it is heat sensitive and it is easily replaced; no soldering necessary. We can get this solid state amplifier at most any auto parts store in the US but I dont know about Espana. On a different note, is driving a V12 Jaguar in the streets of the Basque country like running the bulls in Pomplona? Hasta Luego Amigo
 
Hi John ,thanks so these amplifiers can be repaired? is this amplifier not a square aluminium box next to the distributor? or a black box as you say?
Yes driving around here is funny in these big cars but I am in Galicia near Santiago the basque
county is about 300 Kmts from me I see you also have a few cars yourself?
I have a little collection the 1977 xjs v12,a 1993 xj4o a 1977 mgb-gt which I have restored and a 1977 Rolls Royce silver shadow II which has only done 39,000 miles
things to keep me occupied in my spare time
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Rodney, Your XJS is a VERY early model, You have an aluminum box and they are so rare in the USA that I dont know what is inside of it. What I said in previous message does not apply. Get a new amplifier by Jag part number and remount it in a better position for cooling. If you were here in Alabama USA I could bench test your system and determine the fault and replace it with a black box and I would have to see the inside of your distributor to do this. Usted uno buen hombre als mia corazon. Jack Farrington
 
Hello Jack I am sorry I call you John because it says so there?,
Do you think this could be the problem then?today I started her upand she is fowling nearly all the plugs and running on 3-4 perhaps what controls the injection etc the ECU box ? could I have a problem there? what do you think,? Hasta Luego Amigo Un Abrazo
Rodney


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The ignition amplifier furnishes the signal to the coil to initiate the high energy spark for each plug and it also furnishes a timing signal that is used by the ECU to turn on the fuel injectors at the right time. Yes the aluminum amplifier effects park plug and fuel injector performance. From what you say I would bet that your ignition amplifier is the cause of your problem(s). Since I cannot bench test your ignition componenets, the only choice you have is to get a replacement ignition amplifier and see if it solves these problems. If you think your spark plugs have become fouled due to the irregular running, you might have to clean and adjust them or replace them in order to get the engine to return to 12 cylinder opereation. The other potential source for problems such as you are having is the trigger sensor in the distributor. Usually a continuity check through the leads to this sensor will verify its performance. It is not as vulnerable to heating failure as the ignition amplifier insides are. I cannot tell you whether your earlier aluminum amplifier is repairable since I have never had occassion to open one up. They are very rare in the USA. In an XJS as old as yours, it is possible that your ignition system has previously been adapted to an after market system. Check to see if the ignition amp is a Jaguar part. It should have Lucas identification on it. Do you have Jaguar serevice or repair near your location in Spain? Best regards, Jack Farrington
 
Hola Rodney, It sounds like you have two problems that might not be related. The first is a failu;re with the ignition amp when you are driving and it quits. The second problem is in the fuel injection. It could be the ECU, the coolant temperature sensor for the fuel injection or too high a fuel pressure in the fuel rails caused by the fuel pressure regulator or a blockage in the return line. To deal efficiently with the problems you need to substitute componenets or make measurements of the parameters such as fuel pressure. I think your older fuel injection configuration also has a thermotime switch that controls cold start injectors. If it does, a stuck open injector or a thermotime switch fault could cause this rich running. Espero que essa ayudar, Jack
 
Hola Jack como estas
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Well I Have put some new plugs in today and started her she started straight away but missing I looked at the spark on a couple of plugs and a strong spark started her again and it got to the same as before loads of smoke smelling of petrol and oil and rings of smoke stoped her again and look at a couple of plugs and fouled again oily and petrol,do you think these symptoms are the ignition amplifier? it runs like if you've got the choke pulled out for a long time,what I am worried about is if it is the ECU box .yes here in Vigo we have Jaguar dealer but as you now they are young kinds with a few courses and know less than me which is $$$$$ in labour.anyway thanks very much for your help
Regards Rodney
 
hello Rodney

I had the same problem on my 1979 xjs

and it was the pickup in the distributor that was out of order.

so it's very dificult to find one at a good price,I have bought a new ignition kit from cranecams to replace it.

it took a few hours to fix it in the car, and it work very well.

the price is nearly 230 euros here in france.
 
Rodney, Mio amigo, The advice that you are receiving from other Europeans is very enlightening to me. My advice has been based on availability and after market options in the United States. I believe that you certainly have an ignition problem buto I do not know what your options are to solve it in Espana. It would probably be hard to find your original ignition components in this country. In Spain it would be more difficult. In the US the Crane/Allison solid state conversion seems to be popular and also performs very well. Explore what is available to you in Spain and upgrade your system to a known good system. If your were here, I could bench test it but that is not the case. Get your ignition system cleaned up and then lets evaluate what other performance problems it has.
Hasta Luego,
Jack Farrington
 
Rodney,

I too had similar symptoms on a Series III XJ6 and the problem was the ignition amplifier and the pick-up coil. I replaced both and it cured the no-start and the cutting out issues. If I remember correctly, I paid around $350 for both (XJ6 though) to jagbits.com. This was around half of the Jaguar price and the parts I received were OEM. The labor however was around double the price of the parts. I should have done the work myself. If you determine which system you need, you may want to check prices at www.jagbits.com . They saved me quite a bit of money and shipped very quickly. Best of luck.

Brian
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