92 Xjs 4.0 Wont start

Have a 4.0 XJs , which we jumped started off a battery . Went for a drive and it went no issues.
Next day put a new battery in and it will crank but not fire.
We have spark and fuel . The tachometer is jumping to 3k when cranking but no other clues .
Any help would be appreciated.

Wondering if your fuel pump is running. Might be the fuel pump relay.

I don’t know much about the AJ6, but 3000 rpm on the tach while cranking seems a bit too much. On the V12, starter won’t spin the engine faster than 300-400 rpm…just curious, was it always like that?

Spark is easy to verify, how did you confirm fuel? Again, I don’t know anything about your engine, but from what I recall reading on here, Jaguar did not make it simple to check for fuel pressure on any of the engines from that vintage.
BTW, will it start off of a fuel sprayed into the throttle body?

Thanks Steve…Tried some engine start into the intake and the car try to start, so pulled electical plug off fuel pump to test. Couldn’t get reading however, when I reconnected the joiner plug the car started. I suspect tired fuel pump.