Hey All,

After a few months of ownership I got my 2004 XJR down to one fault which was a "key not in circuit" failure that was causing a park brake fault. The brake works fine but I think a feature was disabled by this.

My water pump went out and the battery went dead. After replacing the pump and the battery they car started fine and idled. I turned off the vehicle and topped the coolant and the car has just started and then stalled ever since.

Steps taken:

1. Added fuel to tank and replaced filter = no change
2. Scan. My icarsoft scanner which is a little better than a cheap one would no longer connect to the ecm though it would still connect to other modules. I updated software to the scanner with no change. I tried a basic OBD2 scanner and was able to read codes.
3. Only code was for fuel rail pressure sensor so I replaced that = no change except new codes appeared for both banks of O2 sensors.
4. Tested the new fuel pressure sensor with a meter. The sensor had a good ground, was getting voltage, putting out voltage and had continuity on all three wires to the ecm.
5. Tested voltage inputs to the ecm and all of the ecm ground wires. All were good.
6. Went through fuses and ground points, looked for loose electrical connections and vacuum leaks. No problem found.
7. Tested fuel pressure at the fuel rail. I was getting 10psi with the key on and it would hold the pressure fine. I tested voltages at both fuel pumps and was able to run both pumps. The low pressure pump was creating 10psi and the high pressure pump was over 40psi at the fuel rail port. Under the start then stall condition the right side pump was receiving a voltage range with a max of 14.4 volts. The left side was receiving a range of lower voltages. After each cycle of start then stall the fuel pressure goes to zero. I picked up a new code for the fuel pump 2 module which I think may of been because my meter was attached.
8. Scratch my head.

I think I may have a problem with the ecm. I have not tested the O2 sensors since I can't explain why both banks would suddenly go out at the same time.
Any thoughts?

 

Your fuel pressure is too low.

I think it should be more like 60 psi or more on an XJR.

 

After running some more diagnostics with a meter I started the car and it is running normally.
My fuel pressure at the test port is 50psi which is low as you pointed out.
I still can't link to the ecm but am able to view other modules.
Fuel flow on the scanner reads 0 at idle and 0.6 when revved.
The scanner shows the fuel pump duty cycle to rear electronic module as 74% while a second row shows "fuel pump duty cycle to rear electronic module 2" as 0%
The fuel pump driver module is getting voltage and putting out a pulsed voltage

 

Get those fuel pumps replaced

 

I replaced the left fuel pump with one from a local yard. $150 and the Jag is running great. This one threw me off because it happened immediately after I replaced the battery.
A good reminder for me that coincidences do happen.

 

Nice!!!! Told ya!

 

Thanks for the help. Do you have an idea of how long these pumps usually last? I am thinking about rebuilding the one I replaced and swapping it back in. Also thinking about the other pump.