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  #1  
Old 04-30-2007, 01:12 PM
dieseldan44's Avatar
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Question Cracking Injector Lines? Investigating what I think is nailing...

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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  #2  
Old 04-30-2007, 03:43 PM
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Quote:
Originally Posted by dieseldan44 View Post
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.
You got it.

I had what I thought was nailing in my '85 that would also go away when the engine was reved, turned out to be a very loose AC belt knocking around. A loose pulley or bolt on something could cause a similar noise too.
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  #3  
Old 04-30-2007, 06:38 PM
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Thanks bgkast! Im hoping its something silly like this.

My first clue as I begin diagnosis: I defintely can hear the same knock in the trunk. I think its coming from the tank. Plugged tank screen or vent perhaps? Ill re set up my diesel purge tank and test.

My initial 'screwdriver to the ear placed against engine parts' technique has not yielded anything. No bad sounds coming locally from any of the injectors, PS pump, vac pump, IP, valve cover etc.

Off to a night of testing.
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'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
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'83 300TD Cali Wagon 210k, wife's car
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  #4  
Old 04-30-2007, 11:34 PM
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Cracked #1 injector, nailing gone. Easy...

Did not have time to travel that injector to another cylinder. Will try that test ASAP...

This pretty much says injector? It also could still be the prechamber? This is what I stand to rule out by traveling the injector Id assume.

dd
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'83 300TD Cali Wagon 210k, wife's car
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  #5  
Old 05-01-2007, 08:54 AM
Gene
 
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ASSUMING what I'm hearing is nailing... I still have it AFTER having the INJs redone with fresh nozzles... diesel man says its ring seal or the chamber.... ??

I;ve been searching on the prechambers to see what I'm up against.

Have also read here is could be an internal leak in the IP. My diesel guy says its very unlikely.
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Old 05-01-2007, 09:35 AM
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dan, before you pull the injector bodies, spray some PB blaster or WD-40 on the threads first... I pulled all my injectors to start a head rebuild, and two of the Prechamber rings came out with the injectors... just a bit of warning for you. I found that popping the wrench instead of just pulling real hard, got them free without disturbing the rings.
John
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  #7  
Old 05-01-2007, 09:51 AM
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Quote:
Originally Posted by vstech View Post
dan, before you pull the injector bodies, spray some PB blaster or WD-40 on the threads first... I pulled all my injectors to start a head rebuild, and two of the Prechamber rings came out with the injectors... just a bit of warning for you. I found that popping the wrench instead of just pulling real hard, got them free without disturbing the rings.
John
Cool, thank you for the tip! I can see that saving a lot of aggravation...

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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
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