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Engine Specific Info and Questions => IDI Engine => Topic started by: 92EcoDiesel Jetta on October 25, 2011, 07:17:07 am
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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?
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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.
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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.
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Side question : what was the value of almost tripling the internal pressure @ idle? What did you gain?
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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?
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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.
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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.
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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...
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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.
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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. ;D
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? 8) ]
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'
(http://img687.imageshack.us/img687/6643/eightoldshims.th.jpg) (http://imageshack.us/photo/my-images/687/eightoldshims.jpg/)
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... :o I'd be grateful
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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. ;D
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.
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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. ;D
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.
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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. ;D
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
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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 :o
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 ;D
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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)
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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)
It depends on the pump. I called up a diesel injection shop and asked them what pressure my pump should be. It's a test spec parameter from Bosch.
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This is all speculation and conjecture on my part since I do not have that much experience with it yet. I think if there is a heat shield leak, the fuel from the injector is all burned and will not show up as a leak via the injector threads. What happens is soot will escape via the leaky heat shield and pack any cavity solid with carbon making the injector very difficult to remove. I had one injector like that on my Ecodiesel when I first acquired it, the injector just didn't want to come out. I was really afraid of breaking the head. It took an hour of back and forth, 1/16" at a timeand lots of penetrating oil to finally get it out and it was packed solid with carbon. You really don't know if a heat shield (re-used or new) is leaking or not till you pull it. The best you can do is make sure the sealing surfaces are clean and not damaged and lessen the chance of a leak by the use of a new heat shield. They cost a dollar each here and is not a great expense. I re-used them temporarily because I had to pull the injectors many times and ran out of new ones, which I had 10 on hand.
It was not a burnt heat shield but rather a burnt nozzle face. I'll try to remember to shoot a pic next time I get the injectors out to put new heat shields in.
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 :o
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 ;D[/color]
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A little less based on graphic he posted on average pump psi. I dropped my idle pressure to 38 psi and am watching my MPG get back the the 50 mark as I continue to tweak it.
Mark is the top row the used shields and the bottom the new? I see some wear marks on them and thus figured they must have been in place once already.
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A little less based on graphic he posted on average pump psi. I dropped my idle pressure to 38 psi and am watching my MPG get back the the 50 mark as I continue to tweak it.
Mark is the top row the used shields and the bottom the new? I see some wear marks on them and thus figured they must have been in place once already.
Important to remember the figure from the average graph and Bosch was for 1000rpm crank and not most idle settings, which on a half decently running engine should be lower [Q basic setting are higher than Golf types for some reason, but I run at about 850rpm or less]. I haave a new graph to offer up and will do so soon.
With the heat shields, none were new but one set had been used once The engine I removed them from took a breakerbar to undo them initially, so I assume they had been in situ for quite a while.
You are indeed correct otherwise. Good to see someone with a backbone ;).
The upper ones were reused another 7 times, two of which are still in the car, but I will replace them, either with the ones you thought were new, or with some truely new ones to match the others...
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Man I am just going to have to buy a Tiny Tach for my car! Then I can get data to you for one more set of data points to average in with the others. I already have the pressure gauge on the IP. I generally try to set the idle near what I think is 850 RPM as that is the number on the yellow sticker over on the passenger strut. So I set the pressure lower because it comes up in a good hurry on my pump and perhaps I should watch it again now that I put of tank of ULSD without my additives of wax and ATF in there. Might be interesting to see how it acts. Kicked out 48 MPG last tank. Still struggling to get to a consistent 50 with the way I drive. It may not be possible. But I will not accept that just yet.
You mean none of those heat shields were new. I thought that was the comparison. Some old the others new, the game/challenge was to figure them out. Do I get a cookie? I really like cookies.
If I ever get a tach set up I will be sure to send data your way. I think you have the best set going that I know of.