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Hello,

My fuel injector for my Audi 80 TDI (1Z engine) is broken (sudden jerking on the highway and black smoke...).
Does anyone know the torque with which the clamp that holds the fuel injector in the cylinder head must be tightened?

Thank you & Best regards - Weini


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Update:

I just replaced the NHG. It should be done in about half an hour, if you're not as stupid as I am and you don't forget the small copper ring at the bottom of the fuel injector...
I tightened the nut with 45Nm. Although I haven't been able to determine the officially specified torque, the old nozzle tightened to approximately 45 Nm.

Hi

The specification is only 20 Nm... however, I also find that to be a bit too low.

IMO, however, one should not consider the tightening torque as a torque value, because, according to experience, many screws seem to "seize" over time (even without visible corrosion), which makes loosening considerably more difficult than tightening.

ulf wrote:

20 Nm

edited: there was an error on my part (to prevent readers from receiving incorrect information )

haehnlein wrote:

15 Nm according to the manufacturer's instructions I tightened them to 12 Nm - no problem

Hi Haehnlein

Are you sure that the nozzles are also properly sealed against the combustion chamber (e.g., oil bubble test from the nozzle replacement article)?

In fact, due to the gear ratio, only one force acts on the nozzle and therefore on the sealing ring, which is approximately half the actual clamping torque.
And that a nozzle can already seal against pressures in the order of 150 bar with a torque of just 6 Nm, is quite difficult for me to believe.

Because the sealing ring must be pressed in such a way that it adapts to the small irregularities and unevenness between the (possibly slightly misaligned!) nozzle and the ZK sealing surface.

And finally, there are sometimes even traces of it: I have seen, after cleaning, several times approximately radially-shaped black lines, as if soot-laden combustion gases had carved a path under the sealing ring into the soft aluminum.

For example, if you run a thin screwdriver over it, you can definitely feel the irregularities, which means the copper material has to be compressed into the nozzle during installation.
Removing the irregularities with a homemade tool took quite a while; it was estimated that about 0.2 mm had to be removed until the entire sealing surface was smooth again.

Therefore, I'd almost bet that at least not Your nozzles are really completely sealed

Hi Ulf,

Command back My mistake, I was distracted by the light bulbs I'm an idiot Iron for injectors, of course, 20 Nm. 45 Nm is definitely too much, because it could damage the aluminum thread -> and then it becomes a problem.

Hello again,

Thanks again for the information!! I loosened the nozzle again and tightened it with about 20Nm (using a 1/4-inch ratchet). With the large 3/4' torque wrench, even 45Nm is quite a bit, but when loosening it with the small wrench, I quickly realized that it was much too tight

Next time, it won't happen again...

Thank you & Regards - Weini

Weini wrote:

I have loosened the fitting again and tightened it to approximately 20Nm

Hi

Based on my experience, this is a fairly "reliable" method for worsening the seal between the nozzle and the ZK - especially if the screw is loosened to the point that the nozzle can only be moved slightly before being re-fixed.

I would definitely perform the oil bubble test for verification purposes, and if the result indicates, I would remove the nozzle again and re-insert it with a new O-ring.