I hope you can help me. My 2005 XJ8 has recently developed a problem. When I start the engine, it runs for only a few seconds and then dies. This happens over and over. No DTC codes came up when I ran a scan. TIA!

 

Off the top of my head....if you are not getting codes and it starts OK, it probably rules out most of the intake sensors and exhaust sensors as they will generally allow running, just rough or invoking limp mode.
Crank position sensor probably OK as well.
My suspicions are leaning towards a fuel delivery issue....fuel pressure dropping due to bad pump or controller going low pressure or over pressure.
Can you check the monitor the pressure with a OBD11 reader?

 

Thanks; I’ll give that a try tomorrow.

 

Missing fuel pressure is obvious for this error. However, OBD readout could be misleading because the fuel pump no longer gets current when the engine stalls. Thus, cause and effect cannot be distinguished.

I would measure whether voltage supply arrives at the pump when the engine is turned with the starter. Also, try to see if the pump runs when it is powered externally.

Fritz

 

flatsix - Thank you for that information.

 

h2o2steam - I tried again today. Key on before starting the engine: 47 psi. Right after starting the engine: 54 psi, then the engine stalls in 2 seconds. I repeated this five times.

 

for me the symptoms indicate that it could be an issue with the immobilizer. I do not know whether immobilizer issues would show any DTCs.
Have you tried whether the same happens using all the keys you have for the car? If the problem only occurs with one specific key, there will be a problem with the transponder in the key fob.
Best regards,
Thomas

 

Thomas-S. - I wondered if it might be the immobilizer. Attempted to reset it by disconnecting the battery overnight and touching the positive and negative lugs together before reconnecting it. Then, I tried leaving the key in position II for 15 minutes. No change; same symptoms. Car starts and cuts out after about 2 seconds. I also tried it with both keys.

 

If fuel pressure is holding around 50psi and not dropping until after engine dies, then somehow the ECU must be telling the engine to stop.
I would have thought immobilizer fault would not let engine start at all, rather than start and cut out, but at this stage everything is still on the table.

Can't believe you are not getting error codes or check engine light.

So what safety conditions would make the ECU cut the engine.....?
No oil pressure?
Over temp?
Crank position?
Exhaust emissions ( not so much and on a cold engine the HO2 sensors are likely not being red yet as engine management is probably running in open loop).

See if you can run some sensor reading checks for temp, oil pressure and crank position.....something has to be telling a fib to want to shut this down with repeatable regularity.

 

Does anybody have any suggestions about how to reset the immobilizer? TIA

 

Yes, you would think that if the immobilizer cuts in the car would not start at all. But going by what I have seen on different cars from different brands, it seems that if the immobilizer does not recognize a transponder, it let's the engine start and immediately cuts it off again, so exactly the symptoms described.

I once had the problem on one of my cars (not a Jaguar) that the problem with the immobilizer did not lie in the keys, but in the sensor attached to the ignition barrel in the car. After replacing that item everything was fine again.

Have you checked the status of the immobilizer light?



Best regards,

Thomas

 

You may need it read with SDD. Anytime the engine stalls a log is kept but only retrievable with SDD.

 

Thomas-S. - I tried all three keys. When I turned the ignition switch to position II, the LED on the top of the facia panel extinguishes. (That happens with all three keys.)

 

OldKarz - Thanks. I checked using SDD V130. I didn't find anything.

 

Yes there would be a DTC (maybe several).

Maybe tool not reading them / not being used as required.

 

When I've seen it, it's code P1582 (*). Even a cheap ELM327 reports such (but not the details stored with the code).

(*) it's a sort of data recorder - very useful

 

JagV8 - Thanks! I'm using a rather high-end Actron scanner. Will try my SDD V130 again but, thus far, no DTC codes have shown up. I hate to say it, but a trip to the local JLR dealership may be required.

 

I think the immobilizer is the wrong way, because the transponder is already recognized when the key is inserted into the ignition lock. If the code is not recognized, an error message immediately follows and nothing works.

The way past the dealership is to measure the power supply to the fuel pump after the engine stalls and while the starter is turning and test the supply to the pump from an external source or by bridging the pump relay.

Both should be no problem for an pump engineer, circuit diagrams can be found at jagrepair.com.

Depending on the results, either the fuel pump and or the current supply can be identified or ruled out as the cause. You can either find a faulty component or search for seletive upstream causes.

Fritz

 

Just for giggles as I am sure you have bugger all else to do....check both F42 (10A) and F32 (5A) in passenger junction fuse box.
They are involved in supply to rear electronics module for fuel pump control.
Also while you are there, check you are maintaining 12 volts present on F32 even after engine cuts and before you roll the ignition key back to off.
Losing 12 volts on F32 could indicate an oddity with your inertia switch (highly unlikely but just want to eliminate things).

I also assume the oil pressure light goes out when engine does briefly kick in.
Honestly, I don't know if the ECM will shut engine down if oil pressure switch doesn't initially acknowledge pressure present, but you would hope there would be some protection feature built into the ECM programming.
Oil pressure switch takes sensor line to ground, so you could always ground the line as a separate brief test to eliminate.