Hello again lads,
After scanning, clearing and running the car for a bit, I seem to be getting P0087 - Fuel rail pressure too low on my '15 3.0 SC. After looking up on the forums, I seem to be getting the exact opposite to what most people experience when getting this error - the car messes up in the low RPM and occassionally gets a rough idle. If I drive it at a constant low-ish speed, i.e. 60-65 mpg, it gets even worse to the point where pressing the accelarator halfway does nothing. Switching over to Dynamic mode seems to resolve the issue and the car goes back to normal. Once I get on it the car runs fine all the way to the redline. What are the usual culprits with regards to the fuel pressure on the 3.0 and 5.0 SC? The high pressure pumps?

 

Do you have the ability to see live and record live data? I think at this point I'd first be wanting to verify that the fuel pressure is actually dropping - i.e. if you ended up recording fuel rail pressure jumping beteen 0 and a high number etc I'd be looking closer at the fuel rail pressure sensor (at the rear of the right bank on the 5.0). Always worth a check of the combined low-pressure pump/level sensor in-tank unit as well: the connectors on these are known to go bad, both on the wires to the level sensor but I've also seen corrosion on the connector on the top, which is easy to spot. Access under the rear seat.

I'm not sure about reliability of the HP fuel pumps - as far as I know they're the same on the 3.0 as the 5.0 - they can seem to "go bad", but mainly in terms of noise more than anything else (SDD has a function to shut the pumps off one by one to isolate a noisy pump). Can you hear (e.g.) loud ticking from the HP pump(s) at idle?

 

Going by live data, occasionally the car would have a sort of a "rough" idle. When checking the live data, when that occurs the fuel rail pressure moves between 420 and 500. If the car idles correctly, the pressure sits at around 420 meaning that when it is idling roughly it is actually because the pressure moves between the correct value and a higher one. As soon as I get on the throttle the value constantly pick up going up to 2800 and sticking there throughout the rev range. (The car is remapped, so I guess getting higher pressure is normal there)

With regards to noise from the engine bay I don't think I hear any loud pump noises, keeping in mind that the AJ126 is a loud engine to begin with.

When I open up the drivers door after unlocking the car I can gear the intank pump going off twice very loudly. Is that normal? Coming off from having a big turbo 1.8T with an aftermarket fuel pump, the one the Jag still comes off as being quite loud.