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Robbie's Guide To The Low Pressure Fuel System
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ThatMartinChap
 


Member Since: 06 Nov 2007
Location: Deepest Darkest Berkshire
Posts: 696

United Kingdom 2014 Discovery 4 3.0 SDV6 HSE Auto Barolo BlackDiscovery 4

Nice write up Robbie - I have a couple of symptoms that I suspect are related but so far not been able to pin down to confirm this.

a/ intermittent vibration at idle. deep bass vibration that can heard and felt through the pedals. It comes on when coasting to a halt and the revs drop from 1k to 750. happens 75% of the time when pulling to a halt.

b/ Fuel breather appears blocked. Getting a pronounced suction sound when removing the filler cap.

It seems that once I remove the pressure in the tank then the vibration does not occur for while but then returns.

Reading your post about using the oscilloscope got me wondering if the pressure build-up in the tank is casing the pump/fuel lines to vibrate...

It might just be me joining two unrelated dots but I thought i'd ask.
 Also Gone : MY14 D4 SDV6 HSE : Barolo Black + Almond
Sadly Gone : MY08 D3 TDV6 HSE : Stornoway + Alpaca + Privacy + BAS Remap 
 
Post #154452314th Oct 2015 11:26 am
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donnylad
 


Member Since: 31 Mar 2016
Location: Doncaster
Posts: 32


great guide, I will have to try this but after reading it I am not that confident, but should be ok.

I dont suppose anybody is in the Doncaster / Rotherham area who has done this before and fancies giving me a hand for some beer tokens?

Smile
  
Post #164578425th Apr 2016 10:43 am
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Robbie
 


Member Since: 05 Feb 2006
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United Kingdom 2013 Discovery 4 3.0 SDV6 HSE Auto Baltic BlueDiscovery 4

Donny to Gainsborough is not a major expedition.

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 Land Rover - Turning Drivers into Mechanics Since 1948

Battery & Quiescent Current Drain Testing

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Post #164580625th Apr 2016 11:45 am
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donnylad
 


Member Since: 31 Mar 2016
Location: Doncaster
Posts: 32


is that where you are robbie?

If so nd you fancy giving me a hand let me know when would suit you and I can pop over mate! Thumbs Up
  
Post #164582425th Apr 2016 12:49 pm
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Robbie
 


Member Since: 05 Feb 2006
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United Kingdom 2013 Discovery 4 3.0 SDV6 HSE Auto Baltic BlueDiscovery 4

I'm at home later this week, so Thursday during the day would be ok. I'm not sure where I am at the weekend just yet.

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 Land Rover - Turning Drivers into Mechanics Since 1948

Battery & Quiescent Current Drain Testing

Diagnostics for:
Defender, FL2, D3, D4, Evoque, RRS & FFRR
A not-for-profit enterprise


 
 
Post #164601625th Apr 2016 7:26 pm
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hgrimmett
 


Member Since: 11 Oct 2009
Location: Bledlow
Posts: 901

2015 Discovery 4 3.0 SDV6 SE Tech Auto Indus SilverDiscovery 4

Great thread Robbie, thanks so much for posting this. I've been having a few problems with Christmas tree lights and bongs after about 30mins of running which can be cleared by cycling the ignition, the car throws the P2290 and P0087 codes. I have already swapped out a new brake switch, lights and fuel filter.

I noticed that it could run without fault at a steady 40mph on the motorway to get me and the family back home yesterday but as soon as it hit a hill it had a hissy fit.

The pressure at the schrader valve seems OK at 6psi but the voltage over the fuse is only 8.4mV equating to about 3.5A at idle so I'm going to go ahead and swap out the pump module with one from AF.

Although no one's done a full write up I'm going to brief myself with Beanie brief post on the number of bolts to find and Jakeboy's photos - wish me luck!!
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Post #165812022nd May 2016 2:26 pm
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jamieroxy
 


Member Since: 28 Mar 2016
Location: Redditch
Posts: 72


Well dropped my tank yesterday to give the intank pickup screen a clean as I know they can block up after 100k as mine was showing 3psi at idle and -1psi at 3000rpm. Was crudded up gave it a good clean put back together checked pressure and now show 2psi at idle and fluctuating and -2psi at 3000rpm. So think a new intank fuel pump is needed. But the truck starts and drove fine but always thought maybe a bit underpowered at top of rev range, no fault code or issues?
  
Post #168657231st Jul 2016 11:40 am
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maplecottage
 


Member Since: 01 Feb 2011
Location: Norfolk
Posts: 3171

United Kingdom 2006 Discovery 3 TDV6 HSE Auto Java BlackDiscovery 3

A daft question perhaps - I have been trying to track down a poor starting issue and have been 'testing' the LP fuel pump.

Pump runs on ignition switch on, fuel flow seems good - if engine is not started, pump shuts down after about 20 - 30 secs. Re-energise the ignition and all is normal again.

Is this normal behaviour or should the pump continue to run as long as ignition is 'on'.

TIA

Steve

PS. 5 out of 6 GP's appear fine Whistle
  
Post #169416620th Aug 2016 10:32 am
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hgrimmett
 


Member Since: 11 Oct 2009
Location: Bledlow
Posts: 901

2015 Discovery 4 3.0 SDV6 SE Tech Auto Indus SilverDiscovery 4

All normal!! That's the TFC way to recharge the fuel lines after a fuel filter change!
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Tesla Model Y LR (22)
Audi TT Roadster 225 (52)
Tesla Model 3 LR (70) (gone)
Porsche Boxster '96 2.5 5spd project (P)
Mini R52 S (54)
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Post #169442120th Aug 2016 8:10 pm
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aman
 


Member Since: 09 Feb 2014
Location: London
Posts: 285

United Kingdom 2005 Discovery 3 TDV6 SE Auto Java BlackDiscovery 3

Fuel filter connections in case anyone needs it:
  
Post #169615125th Aug 2016 5:20 pm
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de7158
 


Member Since: 20 Jul 2013
Location: Queensland
Posts: 15

Australia 2008 Discovery 3 TDV6 HSE Auto Stornoway GreyDiscovery 3

Big thanks to Robbie. Bow down
After reading his guide I decided to throw in a low pressure gauge, clamp on ammeter, relay bridging wire and a drain hose for the engine Schrader valve for a "just in case" scenario. Our trip was about 15,000km across central Australia and the Kimberley.
Now how smart did I feel when we had a fuel issue (thanks Gap 11D BT.....don't leave home without one) and thanks to Robbie's guide, I diagnosed a LPFP fault. Current draw good but fluctuating high/low pressure. Changed the fuel filter but still had low pressure so then moved on the next possible cause.....the LPFP.
Took 5.5 hours from start to go, as compared to at least a satellite phone call and a 2 day wait for Road Side Assist and then most likely a flat bed to the nearest rural town with the time delay and associated costs.
My pressure dropped to the pont where I couldn't continue to drain the tank via the Schrader valve and had to drop it down with 40 odd litres still in it. Filter gauze was completely blocked by a black gunk. Drained and cleaned tank as best I could and did a complete tank clean when I got back home.
I had replaced the LPFP before, and so was familiar with the removal & install sequence.
Cheers
Peter
  
Post #169631625th Aug 2016 10:38 pm
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aman
 


Member Since: 09 Feb 2014
Location: London
Posts: 285

United Kingdom 2005 Discovery 3 TDV6 SE Auto Java BlackDiscovery 3

Hi Robbie
I change my fuel filter every year now and I notice there is always a significant improvement in performance and running of the engine.
Can there really be this much dirt in the fuel that needs filtering out?
Looking at the fuel filter itself I notice one of the 4 connections only has a very fine hole, and it makes me wonder, could it be this very fine hole that is getting blocked and affecting performance (rather than the filter itself getting blocked)
Just out of interest, what are each of the connections for, and why is it important that one of the connections only has a fine hole?
What would happen if the fine hole got blocked?
Would It be better to make this fine hole bigger?


Thanks
  
Post #169684027th Aug 2016 1:48 pm
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Robbie
 


Member Since: 05 Feb 2006
Location: ¯\_(ツ)_/¯
Posts: 17932

United Kingdom 2013 Discovery 4 3.0 SDV6 HSE Auto Baltic BlueDiscovery 4

de7158 wrote:
Big thanks to Robbie. Bow down


Embarassed TVM.

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aman wrote:
Just out of interest, what are each of the connections for, and why is it important that one of the connections only has a fine hole?
What would happen if the fine hole got blocked?
Would It be better to make this fine hole bigger?


The differing bore/port size is to balance system pressure and flow, so don't tinker.

The 4 ports are for normal fuel in/out, plus 2 more for hot fuel in/out to warm the filter. In the old days diesel could suffer in the cold, especially at the filter where the pressure drop induces a further thermodynamic (i.e. Joule-Thompson) temperature drop. The D3/D4 will happily run at stupidly low temperatures.

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 Land Rover - Turning Drivers into Mechanics Since 1948

Battery & Quiescent Current Drain Testing

Diagnostics for:
Defender, FL2, D3, D4, Evoque, RRS & FFRR
A not-for-profit enterprise


 
 
Post #169685227th Aug 2016 2:27 pm
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aman
 


Member Since: 09 Feb 2014
Location: London
Posts: 285

United Kingdom 2005 Discovery 3 TDV6 SE Auto Java BlackDiscovery 3

Okay thanks Robbie
What would happen if the tiny hole got blocked?
How often would you recommend changing the filter?
Cheers!
  
Post #169693327th Aug 2016 4:31 pm
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Robbie
 


Member Since: 05 Feb 2006
Location: ¯\_(ツ)_/¯
Posts: 17932

United Kingdom 2013 Discovery 4 3.0 SDV6 HSE Auto Baltic BlueDiscovery 4

If there is anything big enough to block that hole then your HP system and injectors would already be toast as it is on the clean side.

I change the filter as per the service schedule, nothing more. In fact the only filter I change more often than the book is the air filter.

Thumbs Up
 Land Rover - Turning Drivers into Mechanics Since 1948

Battery & Quiescent Current Drain Testing

Diagnostics for:
Defender, FL2, D3, D4, Evoque, RRS & FFRR
A not-for-profit enterprise


 
 
Post #169705527th Aug 2016 8:54 pm
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