Fault messages - Non start

[XJR308]

Hi Paul

Thank you for your input, it is much appreciated.

This morning I took multiple voltage readings, with the ignition off, around the car and they all came out at 12.73 volts. Tomorrow morning I will do the same test and then again with the ignition on and report back. The car is behaving itself perfectly at the moment so I can’t take any readings when the fault is there. One thing I have noticed while trying to find the fault is that when the ignition is switched on but not started there is a humming from the engine compartment that sounds like a motor running; is this normal?

Regards
Bruce

[ptjs1]

Bruce,

A humming that stops after c45 seconds could be an ABS pump, a consistent humming that might quieten a little after a bit could be the supercharger coolant pump.

Paul

[XJR308]

Thanks Paul
It will be the coolant pump then. I have a similar pump on the Carlton.
Regards
Bruce

[J44EAG]

As you have an XJR, Bruce, the humming motor you are hearing is probably the supercharger intercooler circulation pump. It operates all the time when the ignition is switched on. The pump is located down low under the off side main beam headlight and connects to the lower left hand water inlet pipe on the intercooler radiator. One of the front pipes from the intercooler bricks take the hot heat exchanged water down to the pump. The reliable life span of this small and hard worked little Hella pump is about 130k miles. If it eventually fails, replace with a AVT Bosch metal high flow pump for about one third of the price of a standard Hella unit. Buy via ebay or Amazon for about £135......About £470 for the standard wimpy Hella pump!

I made reference to this pump in Part 2 of my methanol/water conversion article in the recent July 2017 No 7 magazine. The pump makes a big diffference to the way an XJR/XKR/XFR performs particuarly in hot weather. It helps lower inlet air temperatures after the inlet air has been through the supercharger. Anything that can be done to lower post charger air temps to lower levels is to be grasped with both hands. As you can hear that pump running, it is a reassurance that the intercooler circuit is having its coolant circulated. If the sound of the pump stops, this will be immediately felt as reduced power output and is likely to be accompanied by very hot intercooler bricks on top of the engine. If you can`t keep your hand on an intercooler brick when the engine is running, you should assume the little Hella pump has had enough of working in a hot place. Bring out the AVT Bosch pump which has big enough muscles to satisfy the drag racing boys. Highly recommended.

In this image, the larger high flow Bosch pump is on the right.

This pump fits most Jaguar R spec`d cars including X300/X308/X350/STR/XKR/XFR as is suitable for both 4.0 and 4.2 litre cars.

Sorry. Gone off thread slightly!

Mike

[XJR308]

Thanks Mike

Although I have owned the XJR for fourteen years I have not worked on it much as it has been very reliable. it is serviced every 10,000 miles at a main dealer and until now has never let me down. The only thing I have replaced is three coil packs. I keep a code reader in the boot, a spare Genuine Jaguar coil and the necessary tools to replace it.
I have a charge cooler pump on my Lotus Carlton that runs a lot quieter than the Jaguar unit.

Thanks for the info.
Regards
Bruce

[J44EAG]

Forgot to say that there is also an electric aux heater pump on V8 models that you might also hear. It is like a smaller version of the Hella intercooler pump. Those two pumps often get confused when someone goes to order a replacement. Part numbers are critical. The pump is there to assist coolant flow in the cabin heater circuit but also to allow a bit of heat to still be available from a hot engine even though it may be switched off. Quite a useful function in the winter.

Mike

[XJR308]

Thanks Mike
Very useful info!
Regards
Bruce

[XJR308]

This morning I checked the voltage readings again, with the ignition off, across the battery, and then at a ground point in the boot to the positive terminal on the battery and lastly at the engine management fuse box and they all came out at 12.84 volts. I then carried out the same test with the ignition on and at this point the error messages appeared. The readings were now 12.53v across the battery, 12.53v at the ground point in the boot and the volts at the engine management fuse box fluctuated from 12.10v to 12.48v. I then pressed the meter lead pointer a bit harder and everything came back to life! I have taken the power leads off (battery disconnected) cleaned them and re fitted. So far the error messages have not returned.
Thanks for your help.
Regards
Bruce

[ptjs1]

Bruce,

Really good to hear that you may have got to the bottom of the issue without spending any money. We have started to understand in recent years that the interconnectivity of these canbus systems really demands great integrity in the basic passage of current around the car. Spurious lights and fault codes is inevitably caused by a less-than-perfect current flow.

Fingers crossed that you've sorted the problem!

Paul

[XJR308]

Thanks Paul

The upside is I now have a clearer understanding of the electrics on the car.
Bruce

[Andy P]

Glad you resolved the issue,will keep all this in mind if I get a similar problem.
Well done Bruce,
Enjoy your cars,
Andy

[XJR308]

Hi All
Just quick update on my electrical fault. I have used the car and covered over 400 miles without any more starting problems. However this morning I switched the ignition on and waited for the system check to finish and ‘Restricted Performance’ message came up, the engine turned over but would not fire up. So this was a different problem from the previous one. I checked voltage at the various points and they were all ok. I plugged in my code reader and no faults were recorded.
I then remembered that my previous X300 XJR had a similar problem which turned out to be a switch on the gear selector. So I turned on the ignition and moved the selector to ‘N’ and the ‘Restricted Performance’ message went out and the engine now started. It now also starts in ‘P’! So another intermittent fault; I think lack of used is my problem as the car has covered 106,000 miles and this is the first electrical gremlins I have had.
Bruce

[Orkney]

I too get an occasional 'restricted performance' message when I move from D to 4 across the J gate - especially if I haven't used the car for a week or so. I can usually produce the fault at will and even though the message disappears when moving back to drive, the performance is still restricted until the next engine start. I have, on occasion, switched off and on while still on the move to get back to full power if needed.
Perhaps this winter, I might get around to removing the selector assembly to investigate but it's a bit of a faff on the 4 seat Daimler model to get the whole surround off. Not sure how many micro switches are involved and if they are still available - we'll see.
Ian