Member Since: 04 Dec 2020
Location: Cheshire
Posts: 32
LPFP or HPFP? Need clarification from the wider team
Hello everyone,
I haven't posted for a while, mainly because the information within this forum is so detailed that I can normally sort out most issues without even asking. Top marks to the proprietor and its members.
This subject I want to discuss has been widely spoke about in different posts but I feel my issues need a particular thread so here goes.
Bought my 2009 D3 XS Auto 120K miles, 8 months ago and have had a all the usual problems, most of which I have sorted apart from this because I cant work out the route cause.
Issues is i get HDC fault, SP programs off, EPB fault and suspensions lowers. I get this 4-5 times a day on my 12 mile daily commute. Had this for months now. As soon as i stop a traffic lights i cycle the ignition and away i go again.
I have narrowed it down to when I only use slight throttle demand, if I gun it everywhere it seems to happen less or not at all. It will do it, almost without fail, using cruise control at 50-70mph and on slight inclines.
This issues is i have also been chasing a plethora of CAN bus faults which appear from every module but yesterday i also got P0087-00 Fuel rail/system pressure- too low.
Also have a P010-17- Mass or air flow- circuit range/performance (frustrating after new MAF fitted)
Things i have replaced:
New Banner battery
Genuine LR Brake pedal switch
Genuine LR Rear lamps (all of them)
Genuine LR Fuel filter
New MAF- none genuine
Cleaned MAP sensor
EGR Delete
Glow plugs replaced
Instrument cluster failed- Now repaired by Total Tronics
Checked all multi plug connections- All good
Checked TCCM plugs and internally- All good
Checked Earth straps from Enigne to chassis- Good
Checked Earth strap from Gbox to chassis- Good
Steering angle- recalibrated
So my attention is now fuel related.
My question is do I need to start thinking about replacing the LPFP or the HPFP?
LPFP pulling 4.1A at idle, haven't checked the pressure as per Robbies thread but i'll get a gauge ordered.
But what are peoples thoughts on which system Low pressure or High pressure?
Any help would be greatly appreciated.
Jonathan.
13th Sep 2021 8:56 am
PROFSR G
Member Since: 06 Mar 2017
Location: Lost
Posts: 4627
You're not the first one to tackle this issue and certainly will not be the last, and your problem can result as a consequence of one or both sides of the fuel delivery failing.
Generally, the lp side is easier to diagnose once you are aware of the factors which affect it's performance. Primarily, these are the fuel filter being beyond service life, or a cheap filter in place. Clogging up of the lpfp pick up in the fuel tank, or a failure of the pump itself to maintain adequate delivery.
Without removing the tank and checking for clogging internally the other options are as follows.
In the first instance, you should replace the fuel filter with a genuine LR filter, or a quality aftermarket one such as Mahle. If there's no improvement, next is to apply a test to the elec side and then the delivery side. You say you are drawing 4.1 amps at idle, I would consider this acceptable albeit tending towards the lower threshold. Since you do not have a pressure gauge you can get a good idea of the delivery by removing the schrader valve and clamping some fuel hose onto the valve stem. Then jump the contacts on the fuel pump relay (3 & 5) and time the delivery of fuel into a suitable container. I would suggest anything above 1.5 ltrs p/m given current ambient temperatures is adequate. Anything below this is suspect in my opinion, though I have seen perfectly running D3's with delivery as low as 1.3 ltrs p/m, but this really is borderline!
One caveat here though,do not get the relay contacts wrong or mixed up, or you will be in a whole lot of trouble! Use proper terminals or even a flick switch between them to eliminate the risks of accidentally shorting anything in the fuse box! If in any doubt do not proceed, or come back to me and I'll try find some images to assist you. You can use this method to drain the fuel tank if required, just have enough containers to hand before you start. Remember too if you were doing this in winter the readings will be higher due to the greater resistance caused by a higher fuel viscosity.
If you are continuously pumping 1.5 lits or above I'd take that as acceptable, and so the hp side is where your attentions would next be focussed. This is more tricky to get definitive answers from as there are several components which govern it's performance, and they must all work in harmony.
There are two solenoid operated switches in the high pressure pump, the volume control valve (VCV), and the pressure control valve (PCV). Both of which receive information from the ECU via data delivered by a sensor in the fuel rail. (FRPS) Then there are the injectors, and these too can cause issues if one is underperforming, though it is very unlikely given your fault codes. In any case you are now into the realms of a diagnostic tool to observe and monitor the performance of the above components. (GAP IID Blue Tooth)
Within the hpfp there are other components which can fail, the internal transfer pump (ITP), or the pistons themselves can wear causing pressure loss. Often, if the hpfp is failing there will be brass swarf found within the fuel filter when you cut it open with a hack saw. However, this is not always the case as it can just as often be the PCV, or VCV, that has failed or the FRPS. None of the hpfp components are serviceable according to SiemensVDO who manufacture it. This applies to the fuel rail sensor as well, and so complete units only must be installed. There are many instances where owners have attempted to replace the valves/sensors with varying amounts of success. Just like everything else in life, you pays your money and takes your chances!
Removing the hpfp is no small job and requires a new belt and tensioner as well. So as with just about everything LR, start with the simple stuff and work from there.
Further info is available in the Wiki section particularly Robbie's guide to the lp low pressure fuel system. And there are reams of threads and info written by members if you use the search function.yµ (idµ - eAµ) ψ=mψ
13th Sep 2021 4:50 pm
danrjm
Member Since: 11 Sep 2018
Location: Cardiff
Posts: 70
I had the exact same problem with my D3 for about a year. Replaced the battery, switches, etc, with no luck really. It got to the point that, after a few miles, the car would flash up alsorts of errors and I'd have to restart. I took it to a local independent specialist who told me that it's recently become a very common problem with the D3's and some D4's which they think is due to a change is diesel fuel quality which happened a couple of years back. They ran a check in the lpfp and no problem, then changed the fuel rails - apparently this fixes the issue on about half the cars they've seen with the problem. It actually fixed mine for about six months, but then it started flashing up errors again. So, eventually, I had a new hpfp and it's never happened since. The car runs much better and fuel efficiency and power is up from what it was.
So... If it's not the lpfp, it may be worth changing out the fuel rails to see if that helps before going for the hpfp. Apparently, fuel rails should be changed with a hpfp anyway, so there'd be no extra cost but you may save some money if it is just fuel rails.
13th Sep 2021 7:25 pm
Daddy_pig_disco
Member Since: 04 Dec 2020
Location: Cheshire
Posts: 32
Thanks for both replies, I'll try the physical measurement of the diesel that I get from the schrader first.
Update soon.
13th Sep 2021 8:26 pm
PROFSR G
Member Since: 06 Mar 2017
Location: Lost
Posts: 4627
Just unscrew the schrader using a tyre valve tool and slip fuel hose over the stem with a Jubliee clip.
The ign key cycle will only give you 20 secs before the PCM shuts off the relay, so it's best to bypass the relay giving you continuous and uninterrupted delivery from the pump.
Remember too the fuel filter can very often be the culprit here, so do the flow test with the old filter in place, and then again once you have changed it! yµ (idµ - eAµ) ψ=mψ
13th Sep 2021 9:04 pm
LittleG
Member Since: 21 Sep 2013
Location: Wombourne
Posts: 389
Member Since: 04 Dec 2020
Location: Cheshire
Posts: 32
UPDATE
I tried the physical measurement of diesel method as I'm still waiting for the pressure gauge to turn up.
Result was 1.55 litres in one minute @ 4.1 Amps. Ambient 18C.
I think I'm happy to dismiss the LPFP as the route cause?
What do you guys think?
16th Sep 2021 8:23 pm
PROFSR G
Member Since: 06 Mar 2017
Location: Lost
Posts: 4627
I have 3 D3's here right now and only one of them is delivering that much fuel but all run perfectly.
If you have a GAP IID diagnostic tool try a > fuel pump reset< just to see if it helps any and before you fire the big parts cannon. Ideally though, you would want to confirm via diagnostics the hpfp pump is at fault by monitoring the live values of the fuel pressure and volume control.
On a side issue with the MAF fault, check the connections at the plug as well as the condition of fuse 17 in the BJB! And whilst you're at it, check the contacts on number 13 (PCV & VCV) for good measure. yµ (idµ - eAµ) ψ=mψ
16th Sep 2021 9:50 pm
Daddy_pig_disco
Member Since: 04 Dec 2020
Location: Cheshire
Posts: 32
Another update...
I used a 0 to 1.0 Bar pressure gauge to test the low pressure fuel system, and got the following results:
Ignition on, engine off- Just below 0.4 Bar steady
Engine on, idling- drops to 0.3 Bar steady
Cruising in 6th @ 50mph- 0.2 Bar steady
Cruising in 6th @ 70mph- 0.2 Bar steady
Floor it- Pressure drops to 0 Bar and even went in to vac???
Can someone please explain to me if these results are any good? I certainly wasn't expecting the pressure to plummet when I accelerated.
22nd Sep 2021 10:04 pm
PROFSR G
Member Since: 06 Mar 2017
Location: Lost
Posts: 4627
That would seem to indicate the lpfp can't keep up with your throttle demands.
The ITP inside the HPFP feeds the VCV, when you accelerate the VCV calls for more fuel from the low pressure side. The ITP has to find that fuel to satisfy the demands of the VCV.
This ITP demand, together with a failing LPFP (or flow restriction, eg fuel filter/in tank fuel pick up) could cause the lp value to fall further, or even vanish completely.
That does not necessarily mean there is no fuel supply. Rather, the pressure/flow has dropped further as the ITP tries to scavenge/pull enough fuel to meet VCV needs from an already depleted lp side.
This might explain why you saw a negative pressure value when accelerating. If the VCV does not get the juice from the ITP, the PCM will ping you a low pressure DTC, (P0087 et al) and ultimately limp mode is triggered.
Remember, only a fraction of the delivered low pressure fuel is used by the engine, the vast majority of it is returned to the tank.
Did you do a LPFP reset? Sometimes this can be a magic bullet, but either way I think it's probably time for you to drop the tank and inspect the LPFP and pick up for gunk. If you decide to replace the pump, make sure you don't get tempted to buy a cheap aftermarket unit. OEM (Britpart) or LR if your budget will stretch that far.
Tank can be emptied as described in earlier post with suitable safety precautions.yµ (idµ - eAµ) ψ=mψ
23rd Sep 2021 12:39 am
BradC
Member Since: 29 Apr 2019
Location: Perth
Posts: 118
I see negative pressures under heavy load. There is a reason the "description and operation" part of the service manual says : The required supply pressure to the HPP is -0.3 bar to +0.5 bar gauge. The return pressure is -0.3 bar to +0.8 bar
gauge.
23rd Sep 2021 10:08 am
Daley2021
Member Since: 03 Sep 2021
Location: L117ad
Posts: 8
Chasing the same issue probably gunna go with the hpfp
29th Sep 2021 6:31 pm
Daddy_pig_disco
Member Since: 04 Dec 2020
Location: Cheshire
Posts: 32
I've bit the bullet and booked in at a local Land Rover specialist. Hate doing that, like to do everything myself. Luckily mine is under a warranty so if I get a report that points to the pump then i hope to claim it and get it done for free.
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