Suspected HPFP belt issue

[ibuysingleusetools]

First time poster, long time reader (Disco 4 L319 2010 2.7 TDV6).

I am taking to the forum for the first time in the hope that someone out there has seen these symptoms before and can confirm my suspicion that the errors below is a result of a worn HPFP belt or if the pump is in fact stuffed.

PCM-Engine Diesel 2.7L

• P0087-00 (68) Fuel rail/system pressure - too low
• P0191-23 (68) Fuel rail pressure sensor range/performance - General signal failure - signal stays low

The problem occurs under the following conditions:

- Roughly after 30 mins driving
- The engine is not under load, I can be driving along a flat road at a constant speed and it will occur
- The problem occurs less often in colder weather (if at all) on days that are 27 degrees or less

When the problem occurs, it will continue to occur randomly every couple of minutes. Sometimes less, sometimes more.

I have attempted to mitigate the issue by:

- Replacing the High Pressure Fuel Rail Sensor
- Removing the fuse from the Infotainment system (with self installed Car Play) to eliminate electrical gremlins
- Replaced in-tank LPFP

I have not yet tested pressure at the low pressure valve, although it appears to flow well at idle.

After scouring YouTube (mainly LR Time) and other forums it was suggested to log the Fuel Pressure, Volume and Pressure control valves. The image below is a snapshot of the problem occurring. The fuel pressure takes a little while to follow the volume control valve but it's not too different from when it runs normally. There doesn't appear to be any reason for the valve pressure to jump as the car doesn't appear to be changing gear (it's a constant speed and throttle).

What I would love to know is why the volume control value delta seems to go nuts after the problem occurs.

I can provide the whole log for anyone interested in helping me out.

IMG_D72EDA62AAF1-1.jpg

Thanks in advance. Please help me save my disco from the final judgment of my wife.

[ibuysingleusetools]

ok. It looks like I have posted without researching properly. I see Bananas has gone through this whole thing. I have read through the entire thread. What a wild ride. It gives me confidence to have a go at replacing the HPFP.

Not sure what to do with this post from this point (perhaps close or merge with Bananas)?

2011 D4 'Gearbox Fault' warning

[shack]

If that were me, I would have changed the fuel rail sensor as you have, I've not seen that particular fault before.

If that didn't work, yep... Onto the HPFP.

It's not actually that bad a job, but it is not for beginners.

[loanrangie]

Was the sensor genuine or aftermarket ? I've heard of issues with non genuine pressure sensors.

[DiscoJeffster]

You know, I know, we all know, it’s the pump. Sorry to be the bearer of bad news.

[BradC]

The image below is a snapshot of the problem occurring. The fuel pressure takes a little while to follow the volume control valve but it's not too different from when it runs normally. There doesn't appear to be any reason for the valve pressure to jump as the car doesn't appear to be changing gear (it's a constant speed and throttle).

This is pretty much how it manifests. The PCV sticks. So you are cruising along and relatively low load, you maybe hit a strong headwind or an imperceptibly small incline and the car wants a smidgen more power so it tries to open up the PCV. It notices the pressure hasn't increased, so it tries to open it a bit more. This leads to a rapid feedback loop that pegs the PCV command signal (in reality somewhere around 50%). It sits there for ~2 seconds without the rail pressure increasing and triggers the fault. I could cycle the ignition on the road and reset the fault.

I set a trigger in the GAP to cause an alarm when the PCV pegged and provided I got off the throttle (or cancelled the cruise control) when the alarm went off I could unstick it by releasing then nailing the throttle. If you can get the load request off the engine prior to the 2 second timer expiring it won't trigger the fault. I found that *large* valve requests always worked. So throttle stabs would unstick it for a while. I also tried manually exercising the valve externally (essentially a battery and a bit of current limiting) brought me a couple of weeks relief each time.

As others have already said, it's highly likely you need a new pump.

[PerthDisco]

Yep mine would fault several times in a day then be fine for months and fault again it took over six months until I replaced it.

Like the alternator it’s a scheduled replacement item it is so predictable it will eventually fail from around 250 thousand kms.