P38 diesel one way valve mod for fuel line

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nisbeam

Active Member
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201
Location
down in Cornwall
Does anyone know more about this? I was told by a dealer that they often fit a non-LR modification after the fuel pump on the 2.5 diesel to stop fuel surging backwards towards the pump. Some sort of one-way valve. I have intermittent roughness, and occasional cut-out, though most of the time the engine is lovely & smooth. Have fitted a new pump & done the usual checks. Of course it could be an electrical gremlin that may be hard to find, so I thought I'd fit one of these first. If anyone know more about this I would be grateful, sounds like a good idea and cheap (hopefully) modification. Thanks.
 
nisbeam said:
Does anyone know more about this? I was told by a dealer that they often fit a non-LR modification after the fuel pump on the 2.5 diesel to stop fuel surging backwards towards the pump. Some sort of one-way valve. I have intermittent roughness, and occasional cut-out, though most of the time the engine is lovely & smooth. Have fitted a new pump & done the usual checks. Of course it could be an electrical gremlin that may be hard to find, so I thought I'd fit one of these first. If anyone know more about this I would be grateful, sounds like a good idea and cheap (hopefully) modification. Thanks.
Click to expand...

Has anyone tested or swapped your 4th injector??? the one with the sensor on it??
 
Well it has been checked by the local garage though they are not a LR specialist they work on lots and have done over the years. The initial diagnosis was a fault with the crankshaft sensor, which was the fault code that kept recurring. So this was changed & fault code went away, the fault didn't. They suggested the 4th injector sensor as a possible cause but said they had checked and were sure it was OK. When I first had the car (second hand 3 months warranty) a very similar problem occurred and was fixed by a new fuel pump under warranty. So fitted a new fuel pump just in case. problem still there. Of course it is so infrequent it is difficult to diagnose. No error codes showing anywhere. I suspect one of those small electrical faults like a dry solder joint somewhere or loose wire that will take for ever to find. This is why I thought I may try the fuel mod just in case.
 
and you've replaced all the leak off pipe between the injectors and swapped the fuel filter?? go put some shell v power in it for the next few tanks too.. i would say it maybe a fault with the 4th injector. if it's done over 125000 miles it maybe worth changing.
 
Yes new fuel filter (+ all the others) & I just changed all the oils. But I haven't changed the leak off pipe - what is the significance of this & what does it do? By the way it is just coming up to 120,000 miles. I did wonder about Shell V power, or is there some other fuel additive, and do they work? Thanks again.
 
nisbeam said:
Yes new fuel filter (+ all the others) & I just changed all the oils. But I haven't changed the leak off pipe - what is the significance of this & what does it do? By the way it is just coming up to 120,000 miles. I did wonder about Shell V power, or is there some other fuel additive, and do they work? Thanks again.
Click to expand...

v power has ceaners in it, i defo noticed a difference in smoothness of the engine, economy and perfomance. i don't fill upwith anything else now. the leak of pipes are very easy to replace, the pipe is around 4.5 a metre from an automotive shop, i've just recently replaced all mine because i had air in the clear fuel line, it cured it straight away. you can do it yourself, start at the first injector and take the pipe off, cut a piece the same length and replace the old pipe continue with all the pipes. mine looked perfect but when i took then off they all had splits at the ends allowing air in to the fuel line.
 
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Great advice - thanks. Will fill up tomorrow with v power * go & buy some pipe. Will report back here when done , probably after a week or so to confirm results. :)
 
The non-return valve is often fitted to resolve problems of fuel returning to the tank, normally when stopped overnight or longer. If you have problems after the engine has started it`s not likely to help you much to fit one.
As Ladyranger says the sensor needle in 4th injector could be faulty, or sometimes the needle inside the fuel-injection -pump, may I think be a problem. However if you have a genuine new pump this shouldn`t be the case.
When you say new fuel pump is that the in tank pump orthe FIP?
Maybe go to a specialist? May cost a little more up front,or be less convenient, but could be cheaper in long run.
 
It sounds then as if the non return valve will not fix it. This problem usually occurs when driving and not on startup. It was the pump in the tank that was changed. The problem really is that it is so intermittent I could take it to a dealer & they will say "fault not found". If fact, it is not so much like a misfire as a very quick electrical cut-out, just as if the ignition was turned off for a moment then back on. Of course when driving hard or under load this translates to a small "stutter" but when at tickover it can cause the engine to cut-out - it will re-start immediately. This is why I would like to eliminate fuel as a cause. So with luck I am not correct and it is a simple fueling problem. We shall see :) Thanks for you input by the way, all advice gratefully received.
 
Does the orange engine management light flicker on when engine falters?
(Hope that bulb ain`t blown and it shows before start-up). Does it seem worse when temperature (air) is cooler? (like cold mornings)?
Don`t pray for a fuel problem yet tho`. FIP costs about 10 or 20 times more than the supply pump! .... But no need to panic ... yet..
Do as Ladyranger says, first try the leak-off pipes, some v-power will do no harm, and try some additives. As I understand it the additives are a concentrated form of what the fuel companies pre-mix into their premium fuels. My local garage swear by the stuff. And no, they don`t sell it so ain`t trying to turn a quick buck!
 
No, no warning lights, and also no diagnostic codes revealing component failure. That is mostly why I suspect there is nothing serious but it is one of those silly little things that happen to cars when they are 12 years old.
It is just so difficult to find. Had cars in the past that would just stop and spent hundred on garages who could not find the fault. So I think some logic may help solve this, i.e. don't look too deep but try for the common denominator as you suggest. But none found so far. This happens hot or cold and while going slowly or fast (wont say how fast in case there are police reading this) let's just say making good progress on the motorway.
As I said it seems like mis-fire but that is a petrol head term, with a diesel we wont get the same thing but either lack of fuel or electrical problem - either way it will not fire for a moment. In other words it is not a mixture problem as such. Oh well keep looking. Update soon.
 
Right, definately not time to spend a thousand quid looking for a ten bob fault! As many mechanics would say " let it develop", and if it don`t that`s even better!
 
If the vehicle runs normally at all other times take a look at the connections to the fuel shutoff valve on the pump. If the number four injector has an intermittent fault, in it's fail mode the ECU would use a signal from the crank sensor for injection timing. This would cause limp mode but not a complete stop. But it would cause loss of power at high motorway speeds as the available engine RPM is reduced. So checking and cleaning the connections to the fuel shut off valve and number four injector may help. The injector usually works or it does'nt, the only thing that will cause a intermittent fault is a bad connection. Same with the shut off valve.
 
That sounds exactly the same as my 4 year problem. Having a manual it was not the end of the world,when the engine appears to cut, drop the clutch for a second and then away you go,roughness, don't let it tick-over. Despite changing the lift pump, distribution pump, filter head and injectors, nothing helped, UNTIL, I had the ECU modified by Somebody(last week, report to come). All rough running went, no cut outs and a completely different throttle pedal feel, oh, and 31MPG @ 110KPH! The intercooler and "chip" is cheaper than all other answers so I recommend it first. Alternatively how about an ECU swap if you can to eliminate that trouble, not sure if the BECM will allow it, anybody?
 
Thanks Old Traveller, I was wondering about that. A replacement ECU is very expensive, I saw a "refurbished" one for £600, and I would not guarantee it would be OK. The swap out apparently involves some re-programming of the new unit in order to talk to the EcBM. But I was wondering if a chip would do the trick. I was thinking of the Rimmer Bros Power Box 2 Power Box 2 - Diesel Fuel Saver for Range Rover P38 at www.rimmerbros.co.uk
But was of course wondering if it would "by pass" the problem or not.
I am very tempted now after reading your comments. Mmmm, time to start saving perhaps.
 
Old Traveller - did this problem occur when the outside temperature was hot? Just wondering because it seems to be fine today and it is a bit cooler. Having said that it is the first day since filling the tank with Shell V_power, so two changes I suppose make it difficult to see which one has cured the problem (if it has). Probably still a bit early to tell.
 
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