hi,


As the xjr refuses to start for more than 5 secs and runs like a bag of spanners for 4 of them its time to start throwing parts at it.


The OBD reader is now saying there are ZERO error codes!!


If I change the main ECU it will need to be programmed to the car, does anyone know if this can be done with a laptop as its 30 miles to the nearest specialist, but he might be persuaded to come to me. Also any idea of how much would it be?


Or would it be easier to send the unit away and have it checked/repaired,


I know this method is a last resort but it will work out cheaper than the local garage continually testing it, saying they cant find the fault but still stuffing me with a bill!!....if the parts don't work I can re sell them on ebay...

 

Have you checked your fuel pressure? Typically fuel pump failures do not throw error codes on this model.

 

I could here the fuel pump running constantly when the ignition was on but the engine not running. but it was running totally fine, then I turned her off and tried to restart her and nothing.......is that usual???


Im guessing the pump is the unit behind and to one side of the rad???

 

No, the fuel pumps (there are two in the 'R') are in the fuel tank. The second is used only under heavy load and for start-up priming..

There is a supercharger coolant pump and an electric heater pump under the bonnet that you hear.

There is a schrader valve on the fuel injector rail that can be used to test the pressure with a gauge and a Ford style schrader adapter.

 

is the pump packing up in the blink of the eye more likely than it being a relay or other electrical issue considering the problems ive got with her?

 

Yes.

This is due to the way the pumps are designed to operate.

The secondary pump is used to pressurise the fuel rail prior to starting, then it switches to the primary pump. If the primary pump is knackered, it will start on the secondary pump and then die because the primary pump is dead. The ecu can only detect a bad relay, not a bad pump.

One way to test this is to pull the relay for the primary pump. The ecu will then sense a dead primary and use the secondary pump for all phases. If the car starts and keeps running, it is a dead primary pump.

The converse is true if you pull the relay for the secondary pump.

 

thanks Plums, excellent answer.


Any chance of a little direction as to where the relays are hiding.....

 

Here is the diagram

 

thanks guys, checked the fuses and relays and there fine, I cant hear a prime from the pump, not like my old xj40 which primed for a good 3 seconds.....my only concern is this car has been a pup from day 1 with faults, the dash is still showing stability and traction as faults but the obd readers are not registering any faults any more....I still have a gut feeling its the ECU playing silly beggers.......

 

Unless you have a code reader with Jaguar capability you will not be able to read abs C codes. My ECU was faulty and I had it repaired, but it was causing four coils to misfire and I was able to chase the problem back to the ECU by actual codes. Very few systems other than fuel will cause the engine to quit and not throw a code.

 

Can you remember which firm repaired it?

 

ASI in TN USA. I think you will be able to find a similar service on your side. Testing was $55, I believe, and cost applied to repair. Insurance raised shipping to $70, so it would probably be too expensive to send here.

Some one will probably be on to give you a local source.

Automotive Scientific Inc. Your #1 Source for ECU, TCU, ABS, EBCM, Climate Control and Speedometer Repairs

 

Spot on diagnosis Plums!!........pulled the pumps today and put battery voltage to them, one ran the other didn't, 6.5 ohms versus open circuit.


new pump ordered....so ill be able to get her running again to diagnose the bloody gearbox and mad dash board issues........