injector leaking at the halves

[92EcoDiesel Jetta]

I put new nozzles in about 3 months ago and they have been fine with no leaks. I upped the internal IP case pressure a few weeks ago (from 20 psi @idle to 55 psi) and it seems not long after that 2 of the injectors started to leak fuel at the halves. Not a lot, just a seepage that makes a mess over time, does not affect power (that I can feel).

My question is: Does raising the internal IP case pressure also increase the pressure to the injectors?

[8v-of-fury]

The injectors are still opening at the designated psi for them to open, so I don't think it would mean any different to them?

I could be wrong though, but that's how I see it.. The pressure bleeds off when the injector opens.

[vanbcguy]

Yeah there shouldn't be any change to the pressure received by the injectors as a result of changing the pump internal pressure.  The internal pressure only affects the low pressure side of the pump, it doesn't have any bearing on the actual fuel delivery portion.

Any other changes?  Are you sure they're actually leaking at the halves, and not at the return lines?  Often when the return lines are leaking the fuel seeps in to the threads between the two halves of the injector bodies and will cause them to APPEAR to be leaking from there, when they are actually leaking from the return lines.  Those return lines do degrade on their own over time btw.

[wdkingery]

Side question : what was the value of almost tripling the internal pressure @ idle? What did you gain?

[Mark(The Miser)UK]

Side question : what was the value of almost tripling the internal pressure @ idle? What did you gain?

Straining  of seals, partial loss of function of advance mechanism perhaps?

[92EcoDiesel Jetta]

Side question : what was the value of almost tripling the internal pressure @ idle? What did you gain?

FYI, 20 psi @ 1000 rpm is 3x lower than spec. All I did was to bring it back to spec. Result was more power.

[92EcoDiesel Jetta]

Yeah there shouldn't be any change to the pressure received by the injectors as a result of changing the pump internal pressure.  The internal pressure only affects the low pressure side of the pump, it doesn't have any bearing on the actual fuel delivery portion.

Any other changes?  Are you sure they're actually leaking at the halves, and not at the return lines?  Often when the return lines are leaking the fuel seeps in to the threads between the two halves of the injector bodies and will cause them to APPEAR to be leaking from there, when they are actually leaking from the return lines.  Those return lines do degrade on their own over time btw.

Absolutely 100% sure they were leaking at the halves. I took one of the leaky injectors out, relapped and cleaned it better this time and also torqued the halves in 3 stages: 20 ft lbs, 35 ft lbs and 50 ft lbs letting them relax and settle between stages. Installed it and the leak stopped. The other leaky injector I wanted to try something different-I took apart the halves and put yellow teflon tape on the threads and put it back together and installed and leak also stopped.

I had the injectors out and in so many times that I had to re-use the old heat shields. I used Mark UK's method to un-crush the heat shields with a ball bearing and vise-grip. It will have to do for now till I get new heat shields.

[Mark(The Miser)UK]

Re shield reuse, first one gave way at 15 reuses. I will replace the other shields next time.
So I can say, I think, giving a 3 fold safety factor, reuse 5 times.
 Also keep deformation down to a maximum of 1mm...

[92EcoDiesel Jetta]

Mark, how do you determine successful shield re-use? You really don't know until removal + inspection.

The shield has 2 sealing surfaces on the nozzle side and one on the head side. The head side is a flare type seal. The  nozzle side has an outer and inner seal. The outer is a flat surface and the inner is a cone that gets crushed against the nozzle to form a seal. On one of the shield that was re-used once, when pulled, I noticed the outer seal was not sealing properly. There was a burn mark on part of the nozzle face where it should be a shinny ring.

I'll be ordering new shields.to replace the temporary re-used ones. 

[Mark(The Miser)UK]

Mark, how do you determine successful shield re-use? You really don't know until removal + inspection.

The shield has 2 sealing surfaces on the nozzle side and one on the head side. The head side is a flare type seal. The  nozzle side has an outer and inner seal. The outer is a flat surface and the inner is a cone that gets crushed against the nozzle to form a seal. On one of the shield that was re-used once, when pulled, I noticed the outer seal was not sealing properly. There was a burn mark on part of the nozzle face where it should be a shinny ring.

I'll be ordering new shields.to replace the temporary re-used ones.  

Successful is if it does not leak. A true leak will show up with bubbles around the threads from cold. (Not to be confused with bubbling when hot, from boiling diesel which is in the threads between injector and head from other sources). The diesel being there from current or historic leaks from the injector body splits or leakoff pipes.

How do you know when a new seal 'fails'?
In my reuse, the injector is in my hand and it's heatshield, and also the knowledge that it wasn't leaking before I took it out.

The lower bevel is a seal. The crush part is a seal, and if both are doing their job will not let pressure pass either directly up the threads, or into the air gap, and past the upper outer face of the shield.

That upper face IMO, although does seal to some extent is merely the limit stop for the injector to prevent over crushing, with some heat transfer out of the injector. If the lower bevel has sealed, but the crush area has not sealed, then if that upper 'stop' is sealing then the gasses work their way up the sides of the nozzle and carbon it up making injector hard to dissemble. If that upper face is also not sealing, then escape is up the threads, which should be observable.

#1 rule
 I always use the same shield in the same hole.[Same injector too for that matter] Reason being, that a close inspection of the tapered seal of the shield that imbeds itself into the soft flesh of the head is as individual as a fingerprint.  Well not quite that individual, but the ridges are fairly unique as far as the head is concerned and seals by ploughing a furrow into the head.
New furrows in the flesh count as erosion, especially for those who experiment... contrast  with a car that has it's injectors replaced twice in it's lifetime. 
For a while at least, a reused seal actually improves it's seal IMO.

Apart from the catestrophic death of the one seal, initially quite alarming when it happened,  but I'm over 99% sure of safety. [Anyone care to guess why? ]
The 15x reuse resulted in only 4 seal leaks so 4 in 60, or 1 in 15. Any one else had more than 7% leak?

Here's a little test for the bright sparks, but last time no-one, not even CADman dared be humiliated. Nothing wrong with being wrong. When I'm wrong I'll admit it. I'll then seek what's correct.

Below is 8 heatshields, 4 used about 8 times, and 4 used only once. I know the order of the 'mix'



If someone could explain to me how I lost my debit card yesterday, following about six weeks of improved security, after embarassingly losing 2 cards in 2 weeks.... ALL on a Wednesday... I'd be grateful

[92EcoDiesel Jetta]

You lost your credit cards because you used it as a thickness gauge re-setting the shields. The shields became magnetized from the magnetic pick up tool and erased the coding on your cards.

How fast will you see bubbling diesel at inj to cyl head threads from a heat shield leak? Mine are dry but the black burn mark on the nozzle face did not give me a good feeling.

[Mark(The Miser)UK]

You lost your credit cards because you used it as a thickness gauge re-setting the shields. The shields became magnetized from the magnetic pick up tool and erased the coding on your cards.

How fast will you see bubbling diesel at inj to cyl head threads from a heat shield leak? Mine are dry but the black burn mark on the nozzle face did not give me a good feeling.

From dry, a few days.Nothing really definitive, quicker if diesel spilt when priming. Leaks come and go, mostly cured by retrimming the leakoff rubbers.
I try and install them about 2" longer than minimum to allow trimming.

[92EcoDiesel Jetta]

If it's not definitive, then it's not good!

What I am concerned with is if there's a leak past the shield but not past the threads in the head, carbon soot will slowly pack itself into the threads of the head and the spaces below it and make the injector removal very difficult down the road.

You lost your credit cards because you used it as a thickness gauge re-setting the shields. The shields became magnetized from the magnetic pick up tool and erased the coding on your cards.

How fast will you see bubbling diesel at inj to cyl head threads from a heat shield leak? Mine are dry but the black burn mark on the nozzle face did not give me a good feeling.

From dry, a few days.Nothing really definitive, quicker if diesel spilt when priming. Leaks come and go, mostly cured by retrimming the leakoff rubbers.
I try and install them about 2" longer than minimum to allow trimming.

If

[Mark(The Miser)UK]

If it's not definitive, then it's not good!

What I am concerned with is if there's a leak past the shield but not past the threads in the head, carbon soot will slowly pack itself into the threads of the head and the spaces below it and make the injector removal very difficult down the road.

Good grief man It's not definitive because my leak might be bigger than your leak , yet if as you say there might be a leak past the seals but not past the threads then that is not possible. The threads are not tight enough to be a seal. If there is a continuous leak, it will push past the threads and bubble up. How do you tell if your brand new just installed shield isn't leaking? Are you the only one who never has a new shield leak

Put up a picture of your burnt shield please. If it is burnt, then how do you know the fault isn't doing the same to your replacement shield? If I were as cautious as some here, I'd want to find out the cause before risking burning a hole in the head...

 If you want an immediate test just spill a little diesel onto the top of the thread. Doing the air release on the fuel lines is enough to drop a small amount of diesel down in the neccessary place. I bleed my lines every time I put injectors in, which is the only time I look at my heat shields, unless there is a leak.

The heatshields saved amount to over £3 each, so 15 x 4 x 3.00 x 1.50 =$270.

Are you going to be the first to pick the 4 old shields in my little game

[R.O.R-2.0]

Side question : what was the value of almost tripling the internal pressure @ idle? What did you gain?

FYI, 20 psi @ 1000 rpm is 3x lower than spec. All I did was to bring it back to spec. Result was more power.

i thought you were supposed to have like 42psi @ idle (internal pressure)