Hello,

Bit of a narrative here to explain first. Car had a slight head gasket leak so I had the heads refurbished and replaced the head gaskets (and bolts). Afterwards the engine will start, run for a few seconds and stall. I initially verified pre-start fuel pressure as 55lbs and then moved onto running down other ideas around CPS as the tach was sluggish to move upon startup. finally came back around to checking fuel and found that the fuel pressure drops to zero upon startup so it's basically only running for as long as there is fuel in the rail. I removed the rear seat to verify voltage at the fuel pump located on the passenger side of the car (USA) as that pump had 4 wires going to it and the pump on the driver's side only had 2. (I figured the driver's side pump is the transfer pump, not the pressure pump). I verified ground for the black wire but the red wire does not have voltage. I tried to look up fuse locations for the fuel pump but googling that comes up with a staggering array of images of fuseboxes for all kinds of Jaguar models/years so it's not clear to me which fuse(s) controls the fuel pump. I did verify all the fuses in the trunk fusebox were good. I ran a scan and came up with the following codes
B1318 - Battery Voltage low
C1981 - Driver's seat Position circuit
P1000 - System check not completed
P1672 - CAN link, engine control module to air suspension
P1582 - Throttle monitor data available
P0191 - Fuel rail pressure sensor circuit/range
U2524 - Data missing for air suspension

P1672 & U2524 are unsurprising as I have the coil spring conversion
P1000 is unimportant
P0191 makes sense because the fuel pressure in the rail goes away because no new fuel appears to be getting supplied once running

B1318 is curious to me. I have 12.74 volts at the battery and I also have been charging the battery. Grasping at straws and swinging wildly here but is it possible that B1318 is being reported because the alternator has stopped functioning?

Any ideas where I look next? Do I chase the fuel problem or the battery voltage problem?

Thanks in advance,
Rich

 

How many miles?

Over 100k miles and the fuel pump is on borrowed time.

Have the battery load tested.

Fuses listed in the owners manual and electronic copy in stickie

NB R8 is soldered onto PCB and not plug in.

 

It would be unusual for a 2005 Jaguar XJ8 to develop a head gasket leak, but it does happen. Now if it were me, I would make sure that the battery terminations are clean and snug. Be sure to check the earth grounds in the trunk (boot) especially, and perhaps those in the front as well. Also check to see if the battery voltage is at least 14.0 VDC while the car is running. If so, then you know that the alternator is working.

 

Update -

Left battery charger off for a week, battery shows 12.5v. For the 15-30 seconds or so the car runs until the fuel rail runs dry there is a measured 14.5v at the battery. I disconnected the fuel pump connector at the tank, grounded the black wire and applied 12v to the red wire. The car starts and runs for as long as I apply 12v to the pump albeit with the low fuel warning and restricted performance messages, I'm going to guess the ECU isn't happy that the car was running with the fuel pump disconnected.

I verified 12v going into the REM via the brown wire which the wiring diagram appears to indicate is leading out of the fuel pump relay. I also measured 12v at both the yellow and red wires going into the fuel pump.

This has me confused. Based on the symptoms of start/run for a few seconds until the fuel rail empties, I'm expecting that if I switch the ignition to "Run"/P2 that either the yellow or red wire shows voltage to run the fuel pump for a couple seconds to pressurize the rail and then the voltage go away but the voltage does not drop to zero. I would further expect that once the starter is energized that the voltage would jump up again but the yellow and red wires stay steady at 12-14v. So how does the fuel pump get energized? Do they apply power to the pump all the time and then activate it via the ground? Am I looking at this completely wrong?

 

Hello,
Did you ever figure out what the problem was? I have the exact same issue and I can’t figure out what the problem is.

 

No, I didn't. I gave up on it. The car has been sitting at the Jag mechanic shop for a year and he's given up on it too. I've moved on but need to do something with that car. Thanks for reminding me. Later someone did suggest disconnecting the MAF and seeing if that made a difference. Never got around to trying that.

 

Thank you for the response, I appreciate it. I did try disconnecting the MAF but that didn't seem to work. I did splice into the red wire on FP04 pin 4 (the connector near the fuel pump) and connected that to ground and the car seems to run relatively fine that way, although I am sure that provides too much pressure to the fuel rail. By the way to answer your question I believe the way the fuel pump circuit seems to work is the rear electronic module (REM) always provide +12V to the yellow wire that goes to FP04 pin2 then it uses a pulse width modulated (PWM) signal to open and close the ground connection on the red wire that goes to FP04 pin 4 to complete the circuit for the pump power. I read on another forum that the PWM signal is about 150 Hz and modulates between 4% and 51% duty cycle this is what helps control the fuel pressure.

I was thinking that the ECU was shutting down the fuel pump after the car was running for a few seconds but it seems like you disconnected the connector to the fuel pump and always had power between pin 2 and pin 4 which is the red and yellow wires from the REM side of the connector I think the colors get switched to black and yellow on the fuel pump side of the connector. So now I am thinking that maybe it is just an issue with the fuel pump. Did you ever try replacing the fuel pump?

Thanks.

 

Yes, the fuel pump was replaced. It's been a long time but IIRC, before the fuel pump was replaced I had isolated the fuel pump and given it direct power. The car would continue to run after starting but I surmised (as you did) that it would overfuel the engine as there is no FPR return line. My WAG (wild *** guess) is that there is a "start mode" for the ECU where it basically sends fuel and spark to the engine and after it senses it running for X seconds switches to another mode which is the point where the engine shuts off. And as I recall it is fuel related as the fuel pressure goes away so something is telling the pump to shut off. Now that I'm thinking about it, I'm wondering if there is an oil pressure switch or circuit that failed. Seems to me that would be the fail safe I would use to self preserve an engine upon startup.

 

Did either of you reset the inertia switch?

 

I didn't but note that my original post was over 2 years ago and no one responded with any sort of substantive answer back then. Car has been sitting at Jag repair shop for over a year now as they have given up on it and I gave up on it by buying an M5. If someone wants a cheap XJ8L in SoCal, let me know.

 

I tried to reset the inertia switch too and that didn't work. Would any other sensor shut the car down after 10 seconds? TPS, Camshaft position sensor, crankshaft position sensor?

 

I figured it out! I used the SDD (Symptom Driven Diagnostics) and ran the Security - Immobilization Setup after that was complete it started up and stayed run. I drove it around with no problems.

Cheseroo - Thank you for your help, I have the SDD software and cable if you need to borrow it but your repair shop mechanic might have it alright. hopefully this fixes yours too then at least you might be able to get a little more for it if you sell it or maybe just drive it around.

 

Interesting. Yes, I have the SDD software/cable. I'll have to go over there and try it out. I'll let you know what happens. Thank you.

 

As you may already know the SDD is not really all that intuitive to use, the way I got to the immobilization setup was to first go to diagnostic and selected so symptoms like engine wont start, click continue. No codes related to this came up then after clicking around a bit I selected Service Functions at the top menu then Security - immobilization setup was the first item in the list. I attached a photo. Hopefully that save you a few minutes of clicking around. good luck and let me know how it goes.

 

Yes, yes, thank you. SDD is ridiculously un-intuitive. We're a software developer and we'd get replaced if we sent that out. The BMW tools are so much better in virtually every way. This is very helpful. I fired up the laptop that has the SDD virtual on it to poke around and find that the battery won't hold a charge. I ordered another one and I'll be heading over to where the car is after that. Separately, do you know where in SDD one "pairs" the key to the car?

 

Do not skip 'Unrelated Events'. They are often related to your problems but did not trigger with the info you put in the original search!