Looking for some maintenance advice on my 2003 XJR. After a few rough starts, it now will not start at all. Battery checks out, and replaced the starter. When the key is in position 2, dash lights up etc, but nothing from the starter, not even clicks.

 

I would first check the 'power-stud' on the false bulkhead aft of the suspension tower in the engine compartment.
Then if it is not melted, try to 'jump' the starter relay 30/87 terminals in the socket.
Try another ignition key if you are getting a P1260 DTC in the ECM.

 

What do you mean by rough starts ?

 

Thank you for some places to start motorcarman.

Vauxi: A couple weeks ago, while starting it got about half way through the normal start, then suddenly just died. When I attempted to start again it was weak and would not start the engine. After a pause of about ten minutes, however, it started normally. This happened again last week, but worse. Then all it gave me a few days ago was clicks, and finally nothing. Voltage on battery with a jump pack reads good. Mechanic replaced the starter, but now no signal at all from ignition to starter.

 

Ok. I'd look for what motorcarman said and after that engine earth cable.

 

Maybe this will help. also check the fuel cut-off switch (on my first 308, it was bumped and tripped the switch) and try to start with a second key (on my second the first key failed to start the car, the second was able -- I needed to then reprogram both and the valet).

 

If the false bulkhead stud is tight, you might look in the trunk, under the main fuse plastic cover where the positive cable connects. I had a loose nut in there and the car was unpredictable. There are four nuts under the cover. If one is loose, it will probably look like it was hot. Be sure to disconnect the battery cable when fooling with it or at lease be aware that + battery power is live on these connectors.
Best!

 

So some progress, at least by way or ruling things out, with my mechanic buddy:

- Power stud on false bulked looks good.
- Nothing with starter relay
- OBD2 codes are p0335 and p1000

Where would I find the fuel cutoff switch?

 

Jaguar refers to it as the INERTIA SWITCH.

https://www.jaguarforums.com/forum/x...t-fixed-65312/

 

I had a similar situation on the Porsche. and put 12 volts to the starter from a
different battery with the key on. Turned out to be a bad ground connection.

 

In the end the starter solenoid relay must close to close the solenoid on the starter

You can jumper the 3 to 5 on the starter solenoid relay socket , needs a heavy gauge jumper

This will test the starter rotation

You have a specific fuel injector relay other then the main fuel pump relay

In the starting sequence the fuel pump will run for 3 seconds only then off

Once the CKPS sees engine rotation the pump will turn back on for the duration of your drive . this is a safety design

You may have a leak in the fuel line check valves and such that you don't trap enough fuel " charge " to carry throgh to a successful start. fuel line charge is different then cylinder priming

One way to enforce the charge is to cycle the key a couple of times before engaging the starter

You can also jumper the fuel pump on at all times by jumpering socket 3 to 5 , this will eventually drain the battery with your keys in your pocket





There is something about if the engine fails to start on # 1 fuel pump it will command # 2 on

I can see how this can throw off troubleshooting

The ignition switch provides a ground path to command the body processor module to then provide a ground path to close the starter relay

so you have a body processo rmodule in between

The BPM must have other agreements like transmission position and security enable before it will provide a ground parh to close the starter relay

The starter solenoid relay control has power " sitting " on the pulling coil and a ground is provided by the BPM to close it

This control power sitting requires the ignition positive relay in the engine compartment fuse box to close , swapping option ?

So we have 2 things , the starter rotation ( beginning and staying ) and fuel to carry it on forward

 

Since you have mechanic buddy with you. Mechanic can measure the voltage at the starter when you are turning key? Both high current and control voltage. Just looking contacts without touching is less than half of the diagnosis. Measure at the end of the circuit what is really missing and tell us the results. Measure voltages against engine earth and against body earth. If control is missing, then it is either control wire or something else. Then continue measuring with the starter relay as you may allready have done. Does the relay socket have voltage across 85 and 86 pin when you are starting ? Does pin 30 have voltage? if it does jump the pin 30 and 87 together. It will spark a tiny bit but starter will engage instantly if the engine side is allright.

 

It might be a daft idea but have you tried wiggling the gearstick? I've seen a few autos where they don't always detect they're in park so the starter is inhibited. My old XJ40 was one, you had to pull the stick back very slightly, one finger was enough, before the car would start. I got used to it so never fixed it.

 

Or shift into neutral and see if it cranks over.

 

The " not in park " switch is a question if it is a enable for the starter command

Pulling the shift lever slightly out of park gate or detent may also give you a clicking noise from up front as the key barrel lock solenoid

Going back into the park gate fully may be the only way to command or enable the starter command

But if you do hear a click it does tell you the not in park switch is making as a piece of information

You have a rotary shift position switch on the transmission body and a linier shift position switch box attached to the shift lever box up top

I can be incorrect on the X308 and the X308 supercharged is a even different transmission / drivetrain components in the starter circuit