Apologies up front for this long backstory, but I'm not sure what will be relevant or not.
I've had the car since April. It's a 2011 XJL, 5.0 NA, 120k miles. It's run great for me.
A few weeks ago it started this crank, no start issue. It was working earlier in the day, and had been parked in the garage for a few hours prior. Good battery, good gas, etc. Pulled the LP fuel pump fuse to check (good), hooked up a Bluetooth OBDII reader (no codes). A few hours later I tried it again and it started right up. I've driven it daily again since then. Fast forward to this weekend. 45-minute drive, sat for 4 hours, 2 minute drive to store, sat for 20 minutes, pulled out of the parking space and it died a few spaces away. Cranking it immediately after it caught a few times, then died after a fraction of a second. Towed it back home, charged the battery (low after unsuccessful attempts), still no codes, LP fuel pump fuse still good, no leaks.
Ideas on where I can start? Nearest dealership is ~3hrs away. I've just started looking into getting a better (SDD) reader hookup.

 

In most cases i have seen same sympthoms, (cranks well, no start, no codes) it have been Crankshaft Position Sensor. Without impulses from CPS, there are no spark / no injection and no codes, because nothing is missing. Engine managment just dont know the engine are turning over, so...

 

When was the last time your replaced the battery?

 

I will remove and inspect the CPS tonight. If nothing looks out of the ordinary I will order a replacement.
Thank you for the suggestion and I will advise later.

The battery was replaced back in April. It's a Super Start Platinum from O'Reilly.

 

UPDATE:

CPS was good.
I downloaded the app Car Scanner ELM to connect to my bluetooth OBDII reader. It allowed me access to more of the sensors (2 at a time for the free version; ended up buying it later).
From the start I could see the RPM's jumping on crank.


Initial starting attempts with app. Fuel pressure spiked at a very low PSI and the engine caught momentarily.



A few attempts later it actually started. Sounded normal. I merged 2 screenshots here before changing the active sensors.



Continuation from the last screenshot. I changed active sensors to the fuel rail pressure. Once it had been idling for a minute, I gave it a little gas. It started to go up, then died.



I ended up buying the app to have more than 2 sensors active in the plotting. All subsequent attempts to start look like this.

In light of the new data, does anyone else have any ideas or further testing I can do?

 

UPDATE:

It's not the CPS. I was able to get a better app for my Bluetooth OBD2 reader that allowed me to view the actual sensors. I ended up buying the app later in the night to get more concurrent sensor readings.



One of the first attempts to start you can see a spike in the fuel rail pressure, the engine tried to catch a bit but died. At one point between this picture and the next I did see the fuel rail holding a very low pressure, 14-16psi between starting attempts.



It actually started a few minutes and attempts later. I was only able to have 2 sensor readings at a time; trial before I bought it. This screenshot merge had the fuel/air ratio. It settled into a good idle.



I changed the readings over to the fuel rail pressure and just let it idle for a minute. I then gave it a verrry little push of the accellerator; it promptly died.



All of the subsequent attempts to start it looked just like this one. It hasn't started again.

In light of this new data, does anyone have idea on either what's wrong or what I can check/test next?
Assistance is much appreciated!

 

fuel, spark, air - make sure you have all 3.

 

kochtravis, from the looks of things, looks like one of your high pressure fuel pumps failed and it is leaking internally, resulting in it not being able to develop sufficient pressure to run the car. That or the fuel pump in the tank to push the fuel forward is working intermittently. I can say that it is not your safety circuit that turns off the fuel pump in the event of an accident as you are getting some fuel pressure. So, this leads back to either your transfer pump in the fuel tank is failed or one of 2 high pressure fuel pumps is failed. Based on the fact that I am not seeing any fuel rail pressure on some of your diagrams, I would be leaning more towards the rear transfer pump. But, this can be proven by doing a simple pressure check by disconnecting the fuel line going into the 2 high pressure fuel pumps and seeing if you get pressure when the car is put in the ON position (motor not running). Of note, that fitting is a flare fitting. Not sure of the exact size. But, it is the same size as the line that runs across the top of the engine (if that helps). Do not tap into the fuel rail on top of the engine as that is the high pressure fuel rail and you need special hoses to handle the pressure on this line.

 

Thermo, much appreciated for the detailed reply.

Exactly as you specified, I separated the low pressure input on one of the high pressure fuel pumps (rear one because it was easier to get to), opened the door, and fuel came spraying out pretty damn fast. After things were cleaned up, dissipated, and connected back together I tried to start it again. Here are the charts:



Opened the door and connected to the OBD2 reader. I heard the low pressure fuel transfer pump run, looked after and no leaks. Fuel rail sat around 120psi.




Merged screenshots... each legend was from when the arrow points.
Started it up and it ran really rough. At the low end of the RPM swing it would nearly die. Then it almost evened out for a little bit, definitely not a normal idle, then died.



I stayed connected to the OBD2 reader until it timed out. The fuel rail stayed at nearly 2000 psi until the reader disconnected.

 

kochtravis, this is very similar to what happened to me earlier this year. Granted, mine started with a failure of the water pump, but in the process of replacing the water pump, the shop told me that my car would not start or if it did start, it would run like hell. It turned out that I had a failed fuel injector (not sure if it was #4 or #6 injector that failed). But, this was causing the car to run really rich, check engine light to flash, and me to have to keep my foot in the throttle some to keep the engine running. Not sure if this is sounding similar to what you are now experiencing. Not wanting to sound like the bearer of bad news, but what you are describing is sounding very familiar to me.

Of interest, now that the engine is up and running, what codes are you getting now? I was getting a low fuel rail pressure code and numerous misfire codes (pretty much the whole one side of the engine (even numbered cylinders). Once I got my fuel injectors replaced, all was good for me. In my case, I found it interesting that it happened during a water pump failure. Yes, I ran the engine a few times with the failed water pump, but it was never for more than a minute and the engine never really had a chance to get up to temp, let alone hot. Not sure if that somehow hurt my fuel injector. I am more suspecting something got into the high pressure fuel rail and causes the one injector to get stuck open. But, I never could get my hands on the fuel injectors after replacement to prove that (not even sure I could have).

 

RESOLVED:
I ended up purchasing the low pressure fuel transfer pump. It finally arrived tonight and I swapped it out. Aside from it being a pain that I had a completely full tank of gas, it wasn't too bad. It started right up, though it was a little rough (assuming from the air in the lines) but steadied out pretty quick.
Thank you all for the help and guidance. It's been much appreciated!

 

koch, good to hear you got it resolved. Hopefully this will be your one and only problem and you will have many miles of trouble free driving ahead of you.