Fuel pressure relief valve leaking

[JamesMac]

Hi everyone, I have just brought a 2007 Spanish d40 with the 2.5 coming rail diesel as a bit of a basket case. It’s leaving diesel fuel the pressure relief valve at the back of the rail. I removed it and found a copper washer in the hole that I can’t see on the parts break down so I removed it and tried it without the washer and it still leaks. My question is firstly is that washer meant to be there and also. If not has anyone had this problem. I could replace the whole rail I guess but I don’t fancy removing the intake manifold to do that or the 1200 dollars for a new rail if I can help it. Any ideas would be appreciated

Cheers

James

 

[Old.Tony]

Please bear in mind that a couple of times here, I'm trying to just make sure that we get terminology correct, and descriptions correct, so that there's no confusion about where we're at, aimed at making this thread valuable not only to those who have some experience with these, but also to those with limited experience and those who don't speak English natively (we have quite a few international members).

Let's start with the exact location of this problem, because there are two "back of the rail" locations depending on who's describing it. Also, there's a potentially confusing washer involved on the fuel and spill lines, called a "cooper" washer - not a "copper" washer which implies a flat, circular "standard" washer.

There's a kinked tube that runs from injector to injector. At the rear of the engine this tube has a bolt with a cooper washer (shaped a bit like a U when viewed from the side). This tube is actually the spill tube.

There's also a thick tube that runs along the side of the engine and this tube has 4 vertical connections with a metal tube running up to each of the injectors. This thick tube is the actual fuel rail.

On the rear of the fuel rail is another bolt with another cooper washer and a hose connected which returns fuel to the tank via the fuel cooler in 4WD models.

In both cases any washer present should not impede the holes in the bolts which would prevent excess fuel from flowing out to the spill (return) line. The service manual doesn't describe any additional washer other than the cooper washer.

Is there any issue with the fuel return hose (kinks, crushes etc) ?

 

[JamesMac]

Hi tony thanks for your reply, I really appreciate you getting back to me so quickly.

I will try my best to explain the situation in the clearest of English again as I have lost understanding of your description of the kinked line running from injector to injector as my engine doesn’t seem to have that.

Ok let’s start again

I recently purchased a 2007 Spanish build d40 Nissan navava st-x 2.5 common rail diesel. It was purchased with a fuel leak at the back of the fuel rail (end closer to the firewall). When I say fuel rail I mean the cast metal part mounted between the engine head and intake manifold with FIVE vertical holes and 2 horizontal holes. (One in each end). The leak is coming from between the fuel rail and the pressure relief valve that’s screwed in to the rail. I removed fuel relief valve and found a copper washer (a washer that looks like a normal washer but is made of COPPER) inside the hole in the fuel rail. I believe it was put there to try and stop the leak but suspect that it isn’t meant to be there. I refitted the fuel pressure relief valve and tested it and it still leaked. Now a drip rather than a fine mist.

My question is is that copper washer meant to be there and if not what sealed that relief valve to the fuel rail ?

Just to be super clear I am not talking about the Copper washer that attaches the banjo bolt fitting to the back of the fuel relief valve but a washer inside the rail itself

I hope that’s clearer
I have Attached a photo
Thanks guys. James.

 

[Old.Tony]

Ok, awesome, we know what we're looking at exactly now!

There's another spill rail involved, obviously not the one we're dealing with here so let's ignore it. The actual culprit is the FRPS on the firewall-end (engine rear) of the injector rail.

******* of a spot to get to, I should add ... and there's no indication anywhere that I can see of a copper washer.

The pressure inside is really quite intense - 1700BAR, about 24,000psi at full noise. If things don't fit in there perfectly, it's going to leak.

And that includes threads. I am wondering right now, if there was a bit of damage to the thread (possible cross-threading by previous owner?) causing the initially observed misting spray leak, and removing the washer allowed the sensor to bite a little more good thread but not quite enough to fully seal it.

The question then becomes: how hard is it to repair that thread, if it's damaged? Can you put an inspection camera to it and see if it's damaged?

A stainless steel helicoil might do the job. I don't know of any thread sealants that can handle 25,000psi - PTFE tape might not work at all. The best sealer I can find manages 10,000psi tops so I'd be leaning towards a stainless helicoil.

If the thread's not damaged, is there something inside that's stopping the sensor from sitting all the way in?

 

[JamesMac]

Thanks tony. I don’t have an inspection camera but I managed to get these photos. obviously they are terrible pics but I think you can see scoring of the sealing face. I think you’re right about the liquid sealant. I don’t think any loctite product would handle that sort of pressure. Looks like I’m replacing the rail. Anyone have one laying around you wouldn’t mind selling me.

Thanks for your help

 

[Old.Tony]

I wouldn't hesitate - if it were my car - to approach a wrecker and look at a vehicle that had a front-end impact which may have damaged part of the engine (rendering it unsellable as a complete unit) and see if the rail is intact.

eBay doesn't have any fuel rails for the YD25. None.

Try Central Coast 4x4 Wreckers on (02) 4352 2443 and see if they've got anything.

There's also www.niss4x4.com.au in Victoria who may be able to get it for you cheaper than a Nissan dealer.

 

[JamesMac]

Thanks tony. I replaced the rail today with a second hand one and that has fixed the leak. Now I have boost problems. But that’s a story for another thread.

 

[Marked]

Hate to tag my isdue on an old thread, but think it is related -

Could the copper washer inserted behind the relief valve have been intended to seal the valve-to-rail junction in the same way the cooper washer is intended to seal the banjo-to-valve junctions?

I am currently alternating between weeping fuel at the valve-to-rail and banjo-to-valve junctions as I attempt to tighten a new valve/banjo bolt sufficiently to be 100% sealed given the very restricted access. The only u-toob vid I can find shows an alarmingly long breaker bar the poster assures was necessary to both crack the valve seal from the rail, and tighten the new one in place ... I have gone as far as a 27mm ring spanner extension on my 19mm combination spanner (ring end on the valve), but this is only half the length of the aforementioned breaker bar, and hence a fraction of the leverage ...

Edit: just read on another thread that required torque on the valve body is 190Nm ... guessing I need to up the leverage from the two spanner trick, as it is impossible to get a torque wrench on with the motor in situ ... but know 190 is just shy of the "FT" setting on my torque wrench.

 

[BarneyB]

I work on very large diesels for a living.
190Nm by hand is getting up there. You'll need big leverage.
Was that number from documentation or a facebook mechanic?

 

[Marked]

I work on very large diesels for a living.
190Nm by hand is getting up there. You'll need big leverage.
Was that number from documentation or a facebook mechanic?

Facebook mechanic. Unfortunately that is all I have found atm. 190Nm is 19kg on the end of a 1 metre bar ... so yeah; "up there" is one way to describe it.

 

[Marked]

Can confirm a copper washer between rail and valve that the valve is supposed to seal against - remembered I had bought a cheap usb inspection camera/light at one stage.

Might need to fish it out and anneal it to solve my weepage issues.

 

[Marked]

My breaker bar didn't quite rotate to the necessary acute angle, so I ended up sacrificing a 3/4" double hex socket to make a tool to tighten the valve (the only 19mm ones I had were single hex):

Used a bit of 15nb gal tube about 600mm long and shaped to clear the firewall. Double hex is necessary unless you remove the fuel filter for extra swing room - then a single hex socket might work. Didn't feel like anything like 190Nm for final torque - the copper washer may have just been sitting a bit skewiff, making it feel seated using tools of lesser leverage on earlier efforts; as soon as I put my tool on it, it turned that much easier that I had to remove the valve to double check I wasn't stripping thread out of the fuel rail. All looked good so reinstalled, and definitely reached a firm seating point at which I gave it a good "nip" and subsequent running test produced no evidence of weepage.

Unlike the original valve which came out of the fuel rail in pieces (body, mini steel ball, seat and I assume a spring that is now lodged on the side of the block somewhere unseen) the replacement had the internals anchored in place with a few crimps around the end - these crimps may also have been restricting the valve from easily seating at full depth in the hole as they appeared to have been coming in contact with something on close inspection before final installation attempt.

Hope this extra info makes this job more straight forward for someone.