Sorry guys, I started another thread to seek advice on my new analysis on why my Jag's failure to crank up.
see also "93 XJ6 won't start (sometimes)"
https://www.jaguarforums.com/forum/s...ad.php?t=40464

It is like a boy-cried-wolf, as my Jag could start without hesitation and dead-silent from time to time.

after getting great responses from the forums friends, I have tried and checked the Inertia Fuel Switch, Battery Voltage/Amp check, Gear Park "P" Lit, Starter bad ground connection, starter relays check, and etc.

But my Jag mechanics couldn't find the cause as the Jag performed brilliantly at his garage this afternoon every time he turn the key.
His only diagnose is gear contact wasn't in "P".
Also he found my brake pump was weak, when engine running pressing down the brake, both "Anti-Lock" and "Brake" lit up. so.....

Now I have a analogy for all these, I need you guys to confirm whether it is logical. "A poor brake pump leads to inability to start a car". It is very much like the gear wasn't in "P" and car wouldn't start.
Remember back in the 80's, several incidents involving Audi's sudden acceleration, so manufacturers installed the sensors on the brake and gear shift. ie. you cannot start the car if the shift wasn't in "P", you also couldn't start a car if your foot is not pressing down the brake paddle, and because my brake pump running poorly giving insufficient pressure, so the sensor detects as no pressure on brake, so it prohibited the car to start. Sometimes, the pump pressure is running enough to trigger the sensor, it starts just fine. Is this logical? any advice please. Thanks.

 

Refer to my another thread, I found the problem causing intermittent non-starting.

Into the 11th day. the passenger side, under the glove compartment, remove the panel, there are 3 black plastic boxes line up, the first left marked "4. Starter Solenoid" in green, the box slide out with some force, disconnect the wires from behind, open its plastic cover from behind, slide out the entire blue unit, see the Starter Relay on the biggest from the left, it fails to contact and starter-not-cranking when ignition key turn, used the screw driver to push down the contact the starter cranks up even without turning the ignition key but engine won't fire up, so turn the ignition key with screw driver force starter relay contact, engine fires up immediately. Repeat it several times, and it is confirmed ! bad relay contact leads to intermittent non-starting issue. I am going to find myself a new unit but this box has 4 relays controlling also Door Luck and Window Heater,
Any advise on how to repair the Starter Solenoid? (Relay)?

See detailed photo : http://www.flickr.com/photos/10335277@N07/4913634564/