My 98 XK8 convertible starter motor was sticking and playing up so I fitted a new one ...now that's a job and a half! Not long after it was starting fine but now once the engines warm the car won't crank over and I hear a slight thud from my gear lever when I turn the key to crank it. I leave the car and a few hours later it starts 1st try. It definitely feels like there is no power going to the starter I've tried to put it in neutral instead of park but it makes no difference. I thought it felt like the car thinks it's in gear that's why I tried neutral but why would a warm engine be any different to a cold one if it was the gear lever position sensor? Really desperate for some help!

 

Been there done that ...east on a LHD total pig on a ~RHD.....You need a cut down extension bar not over 126mm with the socket to go in from the front and a knuckle.

To testing onthe starter there are two terminals ...large bolt 12v to battery and a smaller one usually white/red to energise the solenoid. . See if you can get 12v onto the red/white wire that should make it crank..let me know and will help you further.

If it cranks when hot then you have a wiring issue with the gear selector often called the XYZ switch . if not starter problem

 

To test the starter wouldn't it be easier to jump the starter relay? In fact the OP might want to try replacing the starter relay just in case it's faulty.

 

Yes any way he can get 12+ on the white /red

 

I have swapped the starter relay with no success I have fitted a new starter motor that works fine when the car is cold. How do I power the starter motor with a live feed by connecting a wire from the battery to the relay female connectors?

 

Length of wire ..strip 1/2 in both ends ..hold one on battery positive and stick the other into the appropriate female

 

From your wiring diagram below, take the relay out - pin 5 goes to the solenoid this is the pin that needs 12v to spin the starter (as in Pistnbroke's post above). If the starter doesn't spin then you have to test at the starter itself.

It's also worth testing that you have 12v on pin 3, 12v on pin 1 when the ignition is on and pin 2 goes to 0v when you are cranking on the key.