My XJ8 4.0 1999 has been inactive or about 8 months. I bought a new battery and filled the tank with 10 liters new petrol.
However although there is strong activity from the starter motor it won't start. Also the radio unit and front seat controls do not work now. However the phone does work. Is it a fuse problem or does it need resetting?

 

You can see if there is fuel being delivered to the engine by using a smart phone with the Torque app to connect to the vehicle PCM through the OBD port via a Bluetooth adapter.

There should be around 3 bar fuel pressure with the ignition in the ON position prior to engaging the starter motor. If there is low or no fuel pressure, the fuel pump may have failed. If there is pressure but it drops whilst the starter is engaged, the CKP may be faulty as it sends a message to the PCM that the crankshaft is rotating. If there is no signal from the CKP the PCM shuts off the fuel pump.

 

Welcome to the forums Chris,

Although a member for many years, I see you are an infrequent poster. Like many of us in recent months, you are also an infrequent Jaguar driver but this is probably not through choice.

I've moved your question from General Tech Help to X308 forum. This is the place to post technical questions about your model.

Graham