Hi, could someone help me to establish if my newly purchased 1986 Jaguar XJ6 Van den plas was originally equipped with a coil with a balast resistor or not ? It has a red Accu Spark coil that obviously not original. I want to replace it but with what ? I have several older coils coming from Jaguars MK2, Etype but I don’t know if I shuld be using them ? If so, should I add a Ballast resistor ? Thanks, I would appreciate your advise.
Jaguar issued a bulletin stating that the six cylinders cars after VIN 421xxx would be fitted with a ballast resistor. Before that, which cars had the ballast is a bit of a mystery.
Anyhow, they are apparently not essential as many guys run without them…including me.
Personally I had best luck with the Lucas DLB170 coils but that was a long time ago. I’m not sure if they’re still available.
Here’s some reading
https://www.jag-lovers.org/xjlovers/xjfaq/coil.htm
Lots more coil discussion in the archives
Cheers
DD
Waldemar,
if you want to restore the original state it would be helpful to tell us more about your car: in particular market, if possible VIN. These cars are fairly well-documented in the official parts catalogues available at https://parts.jaguarlandroverclassic.com/older-vehicle-information.
While you stand a very good chance that your car will function well in the original condition, the mere fact that Jaguar changed their own practice on very similar setups may indicate what Doug has already mentioned: a good coil is a good coil and will run your car just as well. It is crucial though not to mix and match coils designed for stand-alone use and coils designed for use with resistors.
This is what the parts catalogue for XJ6 SIII Aug. 85 onwards suggests. Only the 3.4 litre engines have a ballast resistor; all 4.2 litre engines have the constant energy ignition with the Bosch coil DBC1140 which is still offered, though at a notable markup and interestingly, only as stock for XJ40. The Lucas coil DAC3795 is now offered as Ducellier at a somewhat lower price https://www.jagbits.com/product/DAC3795-X.html.
I doubt you make any mistake with either of them …
Good luck
Jochen
75 XJ6L 4.2 auto (UK spec)
To clarify, the DBC1140 in the illustration has the ballast resistor. The resistor is attached directly to the coil “+” post and is protected by a tent-like tin cover.
Cars using this arrangement used a different (“improved”) amplifier, DAC3848 versus the earlier DAC2087. I’ve never been able to ascertain what the difference in the amplifiers actually is. Something subtle, I presume
Cheers
DD
The MK2 etc used points ignition, Waldemar. basically with ‘6V’ coils - and had a coil resistor for a specific reason. The purpose of the coil resistor for electronic ignition is unclear - and as Doug says - and is often omitted with no ill effects…
Some aftermarket EI specify their own coil, which should be adhered to - but the CE fitted to Jaguars works OK with generic coils - coil resistors seemingly optional…
Frank
xj6 85 Sov Europe (UK/NZ)
Thank you guys for your valuable advise
!