1999 XJ8

The fuel pressure is ok it is when I turn switch nothing happen with the starter no cranking and then the 3rd or 4th time it start right up.

Example of how to check starter motor, relay and ignition switch when I turn switch on it goes thru it system checks.

Sorry, but I have to disagree with the starter diagnosis.

If you turn the key and the engine doesn't turn over, 9 times out of 10 it's the key not being recognized by the security computer. You can verify this by using your other key. If you decide you need a new key, they're $$$ because the security system computer needs to be re-programmed by the dealer to make the car know the key is acceptable.

Rivermerkat,

The security key issue is well known among X300 and X308 owners and mechanics. The FIRST thing the owner is told is to use their other key for a few days and see if the problem goes away. If it does, they come in for a new $75 key plus a programming charge to make the car recognize the new key.

I should add that the other thing that could prevent the engine turning over is the transmission interlock. When you turn the key, the brake is checked for being applied and the gear shift for being in park or neutral. Both of these are small microswitches that can be displaced over time. One at the limit of usefulness would exhibit this symptom. The third thing that would prevent it from starting is the immobilizer, but since this case presents itself as sometimes works/sometimes doesn't, that's obviously not it.

Jaguar gear starters are very reliable. I can't remember the last time I had to change one. Contrast that with interlock and key issues, and it's 99 to 1 in favor of being something before the solenoid itself.

Rivermeerkat,

Respectfully, you clearly aren't a Jaguar mechanic. I am, and have been for over 30 years. I guess I date myself using "mechanic" instead of "technician". LOL

The information you're stating is entirely applicable to the pre-XJ40 cars. Those older cars were incredibly easy to diagnose, but not so for anything built in the last 20 years. I can't tell you how many Lucas M100 starters I've replaced on those older cars, but it is a LOT. Conversely, the number of starters for the newer cars have been relatively few. Once Jaguar got rid of carbs and the early fuel injection systems and went to something reliable and modern, the days of customers cranking their starters until they burned up ended.

The key pick-up for the security system wasn't 100% reliable even in a brand new car in '99. As the car ages, the pick-up moves and the keys get banged up. As a result, they become unreliable. The first sign of a failing key or pick-up is the exact complaint of the original poster. If the problem occurs using the spare key, the pick-up may still be at fault, but you always have the customer test the spare key FIRST because that is the easiest thing to fix and the hardest for a technician to diagnose (customers always present one key when turning in the car for service). If the problem continues using the spare key, you then find out if voltage is going to the starter solenoid (usually not), which then takes you down the usual path of brake switch and neutral switch. The problem is rarely the starter switch itself or the security computer, both of which are in the circuit.