1993 Jaguar XJ6 Jaguar 1993 problem with starting the engin

First question, when was your last tuneup? If this isn't an issue, you need to check your fuel pressure at the rail. When you turn the key to "on", it should jump up to about 44 lbs. If it takes 2 or 3 key on/off cycles to build this pressure, your fuel pump or fuel pressure regulator is bad. If the pressure builds quickly but also drops quickly when key is off, it's the regulator.

There should be a pressure tap on the fuel rail for checking pressure. You'll need to get a gauge that will attach to thios tap. If everything is normal, you should get a pressure reading of 43.5 lbs with key on, or on engine crank.