Infamous Jaguar V12 ‘Marelli Fire’ — I Tested What Actually Happens

The Jaguar XJS “Marelli fire” is one of the most talked-about risks with later V12 cars, and it came up repeatedly in the comments of my recent “Buying a Jaguar XJS V12? This is the year I’d Actually choose” video as a significant downside to the later models — but how does it actually happen, and would the driver notice? In the interests of understanding the problem — and knowing what to expect before ever encountering it — I take my V12 XJS out and deliberately drive it on only 6 cylinders to see how it behaves, what it feels like, and what clues a driver might realistically notice. We look at: what causes the infamous Marelli fire why unburnt fuel is dangerous how the engine behaves on only 6 cylinders whether it feels obvious from the driver’s seat what owners should watch for This is not a repair guide — it’s an experiment to understand the risk and how to recognise it early. If you own (or are thinking about buying) a Jaguar XJS V12, this is something you should understand. Timestamps: 00:00 Intro - the 'Marelli fire' 02:21 The plan - drive on 6 cylinders 02:57 what I'm looking for 03:33 warmed up 04:24 disconnecting injectors 05:23 Driving a V12 on 6 cylinders 06:39 cold exhaust 06:49 engine smoothness 07:24 reconnecting injectors 08:23 starting on all 12 08:59 Driving back on 12 10:03 Immediate thoughts 10:35 summary 13:15 emergency driving with one bank failure #Jaguar #XJS #JaguarV12 #ClassicJaguar #Marelli #ClassicCarOwnership