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Two writeups for the 1996-1999 mk3 TDI have been added. They also apply to the mk4 cars so it's also posted there. I will update the FAQ at the top of the forum ASAP.

TDI fuel injector nozzle selection hints and detailed FAQ - this is probably the most detailed single page on TDI nozzles anywhere.
http://www.myturbodiesel.com/1000q_how_to/multi/TDInozzleFAQ.htm

and

Nozzle/fuel injector removal/installation procedure - includes many notes and cautions that are not in other nozzle writeups. Also fixes the incorrect torque value for injector reassembly that other writeups have.
http://www.myturbodiesel.com/1000q_how_to/multi/nozzleinstall.htm

If there are mistakes, corrections, more info, please make a post and I will update the writeups as necessary.
 
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Already posted in the mk4 forum, the tdiparts link is not correct.

Are you sure about breaking the injector holders? They are what's holding the injector in place so I would be surprised that they can break so easily.
 

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I've read that on tdiclub as well. I don't know how likely it is but I think that the injector holder fork may be a weak part since it's happened to more than 1 person.

When you are loosening the fuel lines, the injector body will be pretty stuck so I doubt there's much stres. When you are tightening the fuel lines after removing the injector I would counterhold it since the injector is not being held by anything else. It will help avoid twisting while you tighten the fuel line.
 

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I wonder how it could be so weak since it's the only thing holding the injector in place. It looks like the lever is designed to dampen vibrations since the bolt is in the middle with levers at both ends.
 

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I don't know either but I read that multiple people had it break. Maybe the holding fork is strong in vertical but weak in twisting. Bottom line is that counterholding it and proper torquing won't hurt. Not counterholding and proper torquing will make you :(
 

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Added some pics and edits. I think the writeup needs an injector body pic disassembled, If not I will just use the pictures from a vw manual. They are cutaway pics too.
 

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I was reading on tdiclub that someone went to pop test a brand new nozzle and it was jammed. It could have caused engine damage if it was not tested before installing. Is it really that common to have a brand new part be defective?
 

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It's possible for any brand new part to be defective but from what I hear, the bosio PP nozzles are individually checked. It could have been damaged another way as well. In any case, if the car runs like poo after you install them, then obviously something is wrong. It's not worth it to me to send them out and then have car down time. If you live close to some place that can test them, go for it.
 

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Who knows, something could have happened during installation or shipping. Maybe they forgot to check that one nozzle.

It won't run as well if 1 is bad, but if only 1 orifice is clogged, then it might not be very noticeable. The idea is that if it's not misting the fuel properly, then fuel can stream out of the nozzle and burn a hole in the piston. That's part of the reason why people are experimenting with using more orifices than the stock 5 nozzle orifices. More nozzle holes of a smaller size, everything else being equal, = finer atomization of the fuel = more power, less smoke.
 
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