Where do I disconnect the injector lines to look for a nailing injector? Right at the top of the injector (not at the IP), right? Just making sure.

I am investigating what I think is nailing using techniques described over and over in the archives. I think the car has done this the whole time I have had it - but - only now am I becoming more 'tuned in' to normal MB diesel sounds. To me it sounds like a truck, which I naively thought was OK until I hear another forum members nice quiet 617 that just 'clicks'.

Symptoms:
-rythmic knock or nail at idle, becoming more consistent at warm idle.
-Once I rev the motor, I think it goes away.
Observations:
-Car has fine power.
-did a disel purge in december, but have only driver the car 25 miles or so since then. Noticed a 15% or so power increase after the purge.
-I have had my lower oil pan off recently for an unrelated repair, and did not see any metal in the pan. Upon reassembly I put my ear to the lower oil oan and did not hear any of the problem sound.
-The noise is coming from the drivers side of the engine I think. (IP?)
-I can hear the noise back near the diesel tank as well. (IP?)

I will post sound files tomorrow, as well as my test results in more detail.

Any suggestions for other tests? Thanks for listening...Im paranoid this could be something bad (rod)...

Thanks,
dd

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'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
'82 300D, 'Tex', 228k body / 170k engine ... summer car
'83 300TD Cali Wagon 210k, wife's car