XJR refusing to start

Hello all,

I have a 1997 XJR6 that is refusing to start. When I turn the key I can hear a clink sound but the engine will not turn over. I supplied the starter motor with an independant 12v supply and the car started first time and drove fine, the returned as soon as the ignition went off.

From research on common issues I have tried the following;

Parking microswitch. I believe this is working, I have tried giggling the shifter and I can hear the switch. There is a warning buzzer if I turn off the ignition when the car is not in park
Fuses. All checked with a multimetre and fine
Battery. Fully charged, I removed it from the car and charged overnight
Cable to starter motor. The cable that runs from the firewall behind the engine to the starter has been checked and appears fine

I dont believe there is an issue with the starter or crank sensor due to the car starting when the power supply was on the starter motor.

Any further advice would be much appriciated.

Thank you

Colin

Colin, welcome to the forums.
Does the car have a starter relay in the system? I have a feeling that they do.

I supplied the starter motor with an independant 12v supply and the car started first time

In your position, in spite of your belief that the battery is fully charged, I’d try a known good replacement.

Ive swapped the relays behind the headlights, no joy

Very good advice. Been there, done that…

Frankie

The car has only driven one mile since I last charged the battery overnight. It was flat today and would barely open the central locking. I will shop for a new battery, it needed one in any case.

Thank you for the advice

Colin

Hi Colin,

Have you checked the security of ALL negative(ground/chassis/earth) connections and transits over/through bulkheads, all the way from the battery to the starter solenoid? Same with positive connections/transits?

Even a slightly corroded or loose connection will present a significant resistance on starter operation.

The starter will draw many hundreds of amps on start and even a slight resistance at any earths or other connections will be enough to limit the starter current significantly.

Consider, if the starter draws 300 amperes on start, then 300Amps x 12Volts( if your lucky!) is 3600Watts (3.6kW). That is a lot of energy from a relatively small battery! Any resistance in the starter cables or connections will limit start current. The starter cabling is necessarily very long if you battery is in the boot(trunk). This long run will present resistance in itself and made even worse if there are and “dodgy” connections.

Suggest you check.

Regards and good luck,

Chris

Sounds like you have a parasitic draw, when you have the new battery installed I would start to check that the car ‘goes to sleep’ after a short time. I.e. the battery is only showing a few milli amps draw. If its more than that start pulling fuses to see which circuit is still partially live.

To do the check you need to remove the neg bat lead and place a digital multi meter in circuit.
You can fool the car into thinking the boot is closed by tripping the latch with a screw driver, that will turn off the boot light.