Fault Codes U2023 and P0087

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Originally Posted by Ean Austral

Found this part interesting , how did you tickle the PCV on the pump. ??

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I manually exercised the valve 5 times. I took a look at the way the ECU drives the valve and figured it was quite gentle in the way it drives the valve closed. I figured if I closed it with "extreme prejudice" if it was grunge in the valve I might just shift it.

I used a pair of crocodile clips and a 12V 1.2AH SLA battery to force the valve closed and got a nice satisfying "click". The valve is quite low impedance, so I wanted a 12V source that was inherently current limited. The cheap, half discharged battery I used did the job. It's only good for less than 2A of current.

I'm going to order a new pump this week, but I'm also going to try a few other ideas with increasing levels of lunacy, because I can.

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Originally Posted by BradC

I manually exercised the valve 5 times. I took a look at the way the ECU drives the valve and figured it was quite gentle in the way it drives the valve closed. I figured if I closed it with "extreme prejudice" if it was grunge in the valve I might just shift it.

I used a pair of crocodile clips and a 12V 1.2AH SLA battery to force the valve closed and got a nice satisfying "click". The valve is quite low impedance, so I wanted a 12V source that was inherently current limited. The cheap, half discharged battery I used did the job. It's only good for less than 2A of current.

I'm going to order a new pump this week, but I'm also going to try a few other ideas with increasing levels of lunacy, because I can.

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mmm if you managed to force it using a seperate power source , I wonder if the issue with these cars is not the pump but the electrical connectors that operate that side of the pump.

cheers Ean

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Originally Posted by Ean Austral

mmm if you managed to force it using a seperate power source , I wonder if the issue with these cars is not the pump but the electrical connectors that operate that side of the pump.

cheers Ean

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TBH I’ve had two connectors that have required contact cleaning to resolve. The steering wheel switch connector and front speaker connectors. Both were giving poor connectors. Would be interesting to apply a good contact clean to the male and female side of the HPFP and see if it behaves.

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Originally Posted by DiscoJeffster

TBH I’ve had two connectors that have required contact cleaning to resolve. The steering wheel switch connector and front speaker connectors. Both were giving poor connectors. Would be interesting to apply a good contact clean to the male and female side of the HPFP and see if it behaves.

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that will be my next move , checking the electrical side before I do a pump change .

Cheers Ean

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Originally Posted by DiscoJeffster

Would be interesting to apply a good contact clean to the male and female side of the HPFP and see if it behaves.

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I did that months ago. The ECU is pretty good at picking a duff connection on those solenoids as they are such a low resistance (and setting a code). Also given my particular failure mode can be "driven around", I'm not really suspecting an electrical fault.

Don't let me stop you trying however. I'd love to be proven wrong.

One thing I have noticed looking at the various PCV constructions is they all seem to use a flooded design, where fuel is used to cool the solenoids. That'd make the ingress of grunge or gum quite likely to cause issues. What I can't reconcile is anything large enough to cause the solenoid to gum up or stick should be large enough to either block and injector or be prevented from reaching the pump by the filter.

Would you consider the gauze filter on the lpfp as a source of gunge? Our tests show the fuel pressure drops when the accelerator is applied.

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Originally Posted by orville

Would you consider the gauze filter on the lpfp as a source of gunge? Our tests show the fuel pressure drops when the accelerator is applied.

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If the filter sock is a source of grunge it should get caught in the main filter.

I would expect the fuel pressure to drop when the accelerator is applied. Mine starts at 0.4 bar, that drops to 0.3 bar under running conditions and drops to slightly under 0 bar when doing a full noise blast in 3rd gear. Oddly enough under heavy braking it rises to nearly 0.5bar.

Thats all within spec, even if a bit low. The important part for me was the fuel pressure never drops when the HPFP faults. It stays a solid 0.3bar. As far as I'm concerned that rules out the low pressure system.

i had to drive 50ks with the gauge cable-tied to the windscreen wiper arm until it played up.

We did the same pressure test on a working D4. Pump doesn't drop below 0.5 bar when running and lowest is ,0.4 under revs to 4000. The D3 drops to 0.2. The D3 fails when coasting or gliding but not under acceleration. Not convinced it is the Hpfp.

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Originally Posted by orville

We did the same pressure test on a working D4. Pump doesn't drop below 0.5 bar when running and lowest is ,0.4 under revs to 4000. The D3 drops to 0.2. The D3 fails when coasting or gliding but not under acceleration. Not convinced it is the Hpfp.

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I am going thru the same issue with my D3. Faults only when coasting , code is Low fuel rail pressure, but only if you shut it down as soon as it faults. If you let it run the faults grow to include a gearbox fault , suspension fault , park brake fault and lucky if you can do 20km/h. Bloody scary when you have a 3 trailer road train up your clacker with no where to pull off the road.

I also struggle to believe the issue could only be the HPFP , as it is so random , I am going to spend some checking the electrical side of things , altho I have purchased a HPFP plus the other bits needed for a pump change.

Cheeers Ean

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Originally Posted by Ean Austral

I am going thru the same issue with my D3. Faults only when coasting , code is Low fuel rail pressure, but only if you shut it down as soon as it faults. If you let it run the faults grow to include a gearbox fault , suspension fault , park brake fault and lucky if you can do 20km/h. Bloody scary when you have a 3 trailer road train up your clacker with no where to pull off the road.

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Have you tried turning it off and back on again? Then again, I'm not sure what might happen with an auto, but with the manual box I just flip the ignition off and back on and keep driving. With the van on the back I don't even feel it as it only ever happens under low load while cruising.

In my case I am absolutely *convinced* it's the HPFP, specifically the PCV sticking. I can see it stick on the live data from the IID. The system calls for more juice, the PCV is commanded to close and that continues until the duty cycle reaches about 55%, sits there for 2 seconds and the fault is raised. When I see the duty cycle shoot past 40% I get off the throttle and back on again. That makes the ECU drive the valve back open and when it is subsequently commanded closed as I get back on the pedal (most of the time) it shoots past the sticky point and all is good.

If it was the LPFP or associated filters/pipe work a cycle of the throttle pedal wouldn't make a difference and I'd see it on the low pressure gauge as the fault was occurring. If it was a physical fault in the HPFP itself I wouldn't be able to get sufficient fuel pressure, and yet I can get >1600 bar under full load immediately after the fault was driven around. If it was a wiring or connector fault I wouldn't be able to drive around it, the ECU would be incapable of making the valve go where it wants. Therefore it *must* be the PCV, and as they can't be changed independently of the HPFP, by extension it requires replacement.

I have one more thing to try, and this is the longest of long shots with plenty of potential for disaster.

The VW community swears by Liqui-Moly Diesel Purge. Diesel Purge is a light refined hydrocarbon and a cetane improver (to make it burn more like diesel and stop it blowing holes in pistons). The light refined hydrocarbon cleans deposits that diesel doesn't. It's basically what the yanks call naptha or we know as Shellite. I keep litres of the stuff around as it's the ducks nuts for cleaning anything exposed to engine grunge. It works on deposits that both petrol and diesel find hard to move (yes I've tested that many times) and evaporates without a trace.

So, my last resort is to make ~8L of my own "diesel purge", drain the tank/filter, put this mixture in the tank and run the PVC & VCV through several "crank the engine, exercise the valves" cycles to see if it cleans them out. If I put the return line from the pump into a jar it should be obvious if *any* cleaning is occurring. The cetane improver in "Diesel Purge" is 2-Ethylhexyl nitrate, and Amsoil make a "cetane boost" which is entirely 2-Ethylhexyl nitrate. So some of that, Shellite and a bit of lubricant should do the trick.

I have a spare rail pressure sensor, and according to the Siemens writeup on the ECU it won't even try to fire the injectors until it sees a pressure > 150bar. So having the spare plugged in reading 0 should mean it never tries to fire up and I can just cycle this stuff through the fuel system.

I'm pretty convinced the actual fault is wear in the valves (in exactly the same manner that makes the AC compressor displacement valves stick), but until I can get one to dismantle that remains a best guess.

Anyway, best case it prolongs the life of the HPFP. Worst case something goes wrong and I kill the in-tank pump, destroy 6 injectors and burn holes in pistons.

I already have a new pump and associated hardware in my LR-direct shopping cart, I'm just waiting on "an opportune budgetary moment". In the mean time, I might just see how much more damage I can do.