Lucas ignition system failure (pre-1989)
Symptoms
Misfiring, rough idle, hard starting, power loss, sometimes total ignition failure.
Cause
The Lucas CEI (Constant Energy Ignition) system uses an amplifier module, a pick-up in the distributor, and associated wiring. The amplifier fails (heat-related), the pick-up air gap drifts, and wiring connections corrode. Each bank of six cylinders has its own distributor, so problems can affect one bank while the other runs fine, a distinctive symptom of V12 ignition faults.
Fix
Replace the amplifier module (carry a spare, they fail without warning).
Check pick-up air gaps.
Clean all connections.
Fit electronic ignition conversion (Pertronix or similar) for long-term reliability.
Upgrade to the later Marelli system if possible, it's a significant improvement.
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