Jag XJS v12 no start

Yes fresh fuel would be the first thing to change along with the filter, then check you have fuel pressure and the distributor advance isn't seized, for spark check with a spare plug as you would on any other car. They are pretty simple really the only mad thing is the ignition vacuum system which won't affect starting, there's just 12 of everything. if you have good fuel and spark and no run might it be worth checking the temperature sensor resistance, it's the main thing which controls cold fuelling.

If all else fails try few squirts of easy start in each air cleaner, if it fires for a couple of seconds your problem is fuel.

It's worth downloading Kirby Palm's book as well, gives loads of info on these.

Far from an expert on these, but I’m sure I read, saw somewhere that they’re very susceptible to weak spark/poor distributor/leads