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Discussion Starter · #1 ·
Don't.....Unless its free/under warranty.

At least, not just yet.

Try adding that 2.5mm shim to the fuel rail pressure release valve first, that the select little group of go faster idiots has been playing with. Should cost almost nothing, compared to replacing the qcv/scv.

See what happens...

I've seen some evidence that a qcv that behaves slightly out of range, will just up fuel pressure a little bit, mostly at idle and low throttle. The shim would be just the trick to make the system less finicky to fairly small changes in fuel pressure, which are nothing compared to the increases the go fast crowd is using, so don't worry about blowing up the fuel rail...
 

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Hmm, seems like a 'top tip' to me for the D40 owners :thumbleft:
Woz :salute:
 

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After seeing the valve on your other thread I can`t see how these valves can all have identical pressure settings as there is going to be some slight variation in them all.
The shim set relief valves I would work on would need pressure adjustment to keep them up to factory specifications.
 

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Discussion Starter · #4 ·
Yeah theyre all fairly crude parts but they play such a critical role in keeping the ecu happy. A little more fuel pressure because of a little variance in the qcv, and some of these crude little things play up.

Of the two, the fprv is much cheaper to mod. Yet the Nissan policy is not to ****** with any part of the fuel rail, just to replace the entire assembly, which costs an arm and leg, as we all know.

Give this a go first when the other factors have been checked (fuel filter, maf), youve got little to lose.
 

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I have shimmed 3 so called faulty rails by Nissan. All are still running with out any more issues since. These 3 are on top of the 3 I've done to my own motors.
 

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Discussion Starter · #8 ·
The shim indeed places a preload on the spring. The stock shim is 1.5mm. Add another 2.5mm shim or replace altogether with a 4mm shim.

The valve is held together by nothing more than a crimp around the cap. Carefully pry the crimp open while holding the valve in a vice, so that you don't lose the little ball bearing and the other small parts. Add the shim, put back in vice and recrimp around the cap.

The valve body itself is M22 in size, the spill tube on the back end is secured by an M13 bolt. The crimped cap is the end that screws into the fuel rail itself.

FPRV on the leftside of the fuel rail (Andy's pic):


Prying the crimp open in a vice:


Catch everything in a magnetic pan, the thicker extra shim seen on the left:


All parts neatly arranged before being put back together and the cap is recrimped (Fashraf's pic):


As Diggerman mentioned, it's astonishing that such a crude and simple part is playing such a major and crucial role in controlling an advanced high pressure common rail fuel system.
 

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Okay… I thought you are shimming the pressure control valve.

messing with FRPV is something I would not do or recommend , it is a safety valve meant to keep a limit to the pressure in the system and with this shim the safety is gone and in case a fault, causing a pressure spike, the fuel pump could be cracked.
I saw this happened in Toyota truck but I never understand why, now I know…
 

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Discussion Starter · #10 ·
Adding 2.5mm of shim on the D40 is a tried and tested performance mod, navara1 has already done a handful, and the shim is now even part of fuel pressure chips coming out of Thailand (Powerlab) and Australia (Chip it).

In this case we are not making use of the ability to run much higher fuel pressures as a go faster mod, but just to make the system less prone to go into limp mode.

The extra shim doesn't do away with the emergency spill function, the spill threshold is just elevated by an amount that seems to be reasonably safe over the last 4years or so, on countless high powered D40s.
 

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Discussion Starter · #12 ·
Roughly around 220 MPa will be the new threshold. I keep my max fuel pressure at about 210 MPa.

If one would add the shim solely for reducing the occurrence of limp mode, adding another 1.0-1.5mm could well suffice, my gut feeling tells me..
 

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Discussion Starter · #14 ·
We drove around with a borrowed Consult for a while, adjusting fuel pressure in the cabin (on the fly), which is possible on the Powerlab FPCR fuel pressure controller i run, until we just reached limp mode.
 

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Discussion Starter · #15 ·
Just wanted to add that the manual discribes testing the fuel pressure relief valve by turning fuel pressure on the Consult up to 180MPa, rev to 4000rpm for at least 5 seconds, and check if fuel comes out of the spill tube (EC90).

If fuel does come out, Nissan specifies replacement of the entire fuel rail. So, the factory max fuel pressure should be slightly above that 180MPa mark.
 

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Bluenavara said:
Just wanted to add that the manual discribes testing the fuel pressure relief valve by turning fuel pressure on the Consult up to 180MPa, rev to 4000rpm for at least 5 seconds, and check if fuel comes out of the spill tube (EC90).

If fuel does come out, Nissan specifies replacement of the entire fuel rail. So, the factory max fuel pressure should be slightly above that 180MPa mark.
This can be done with any obd scan/reader if you don't have the nissan Consult to hand. The 220MPa serge states is around the mark. Same works on the 190ps trucks too.
 

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Discussion Starter · #19 ·
A friend of mine with a bone stock 09 D40 had persistent troubles with limp mode until two months ago, and Nissan was about to replace injectors and fuel rail. The quote was about 4000euro. He declined...

For the last two months he has added 200ml of two stroke to every tankful, and he has not had an error ever since...
 
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