My 1987 V12 XJS Cabriolet has developed an ignition problem. I am trying to follow the diagnostic steps in the manual to determine the problem, but I have run into difficulties finding the three ballast resistors. They are supposedly connected to the Lucas amplifier, but I haven't been able to track the wires to them. Does anyone know where they live?

Submitted by dstone@gi.alaska.edu on Fri, 07/01/2011 - 18:31

Thank you all for your help. You got me onto the right circuit diagram and the right diagnostic tests. We found that the culprit was the pick up coil. Now all is well.
Thanks again.

Submitted by stevejag@sbcgl… on Fri, 06/17/2011 - 00:13

The power resistor box at the right front of the engine compartment are for the fuel injectors though, rather than the Lucas ignition. The ignition on the 1987 V12 did not use any ballast resistors. It did however, use a second ignition coil [mounted in front of the radiator] as a capacitor to increase the main coils output. They did that to make up for the short dwell times, meaning short time intervals between cylinder firings with 12 cylinders.
A bad or disconnected 2nd coil can definitely lead to misfires by causing a low ignition output.

Cheers,

Submitted by silver007@shaw.ca on Thu, 06/16/2011 - 21:57

I believe the HE engines do not have ballast ressistors.they do however have the power resistors on the PS inner fender just across from the rad.......in a alluminium rectangular box, with the connectors coming in at the bottom of it.

Submitted by SE98-32482CJ on Thu, 06/16/2011 - 21:52

Doug it was--I wanted to tell him to go to the Green pages in the factory manual but not sure that is what he has. you are right--let's start with the problem!

Submitted by dougdwyer1@com… on Thu, 06/16/2011 - 20:51

Dave, I think in in the part of the manual that covers the older "OPUS" ignition rather than the later "CEI" ignition that your '87 has. The CEI doesn't use ballast resistors.

That might be what George was leading up to.

What problem are you having?

Cheers
DD