1991 Jaguar XJ6 gets fire won't start

Have the fuel pressure check to rule out the fuel pump

Old mechanic's rule; If it's got spark and fuel it has to run, maybe not well, but it will run.
Do you have spark at the plugs? Assuming spark and valve timing are "OK", we'll go to fuel. Checking fuel pressure. Disconnect fuel line at the fuel rail and place into a coffee can or similar container. Have someone crank the motor and see if fuel sprays into container. Do this carefully, you don't want a fire. If you have fuel, check injector pulse with a tool called a "noid light" plugged into an injector harness lead. Any good parts store should be able to get you one. The noid light should should blink as the motor is cranked. If not I would replace the ECU. Other sensors on the engine influence the injector pulse, but the ECU controls the on/off. If any of these "other sensors" are malfunctioning, you should have a check engine light and stored trouble codes in the ECU. Good Luck.