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Discussion Starter #1
Hey folks, just finished service B on my 2005 E320 CDI and found... an all messed up injector. Injector #5 is shrouded by what looks like a swath of burned tar. See pictures below.

The #5 (reminds my of a movie from the 80s) is not oily - it's dry, all covered with burnt, baked-down and pretty hard to scratch off black substance, which I'm not sure what it is. All other injectors (except #6) all look fine, dry and clean.

There's no diesel smell, nor a burning smell. The car doesn't report anything unusual, at least nothing related to CDI rail module (checked with STAR). Gas mileage is OK, not outstanding, maybe 2-3 MPG lower than were I want it to be.

With engine running, no diesel is sprayed around and everything stays dry. I can clearly hear a ticking pops of air hissing around #5. I can actually sense with my fingers a light air stream seeping out around the foot of the injector with the same ticking pattern, just like air bubbling out from a fish tank air pump tube, if you know what I mean.
Should I rev up, the ticking accelerates along with the engine speed, telling me it must be linked with the injection cycle. The engine runs smooth, without shaking. Should I pull the injector connector out, the engine continues to run, with slight, yet noticeable, detonation. As soon as I re-connect #5, the engine runs sooth again, telling me that some injection is indeed happening in #5.
I should say that immediately after pulling the injector wire out I got the check engine light. Checked with STAR and, sure enough, there was a CDI rail module injector #5 failure code set as STORED. I've reset all codes, then re-ran a quick check and nothing came up. The car has ~250k miles and all injectors are original.

Does it look like my #5 is gone? Should I replace it or check anything else? I have not touched the injectors on my car yet, only the glow plugs a couple years ago. So, I was hoping to get some piece of advice first. But I will not hesitate to do what it takes.
 

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As stated in the previous comment this is called black death. Replace the copper seal in the buttom really cheap. More labour may be involved in removing the injector if it is stuck.
 

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Read, read, read. The melted plastic can hold the injector pretty strong and main thing on removal is to get it on hot engine.
Broken bolt lead to lot of headaches, so soak it with oil for several days.
Lot of remedies how to clean melted plastic, but suppose carburetor cleaner works well.
Beware that valve cover is pretty thin and don't apply much pressure on it.
 

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Best pictures I have seen on what black death looks like. So the Diesel fuel turns into nearly plastic?
Everyone states that it is the engines "foam" cover that melts and causes all the gunk. My number 1 injector just started leaking (or I should sat seeping) and the small puddle around the injector was hard like carbon. I picked at it with a small screw driver and blew air there and it went away. I should have taken a picture.
The bottom of my foam cover does not have any marks on it. So, I would like to see what the underside of the cover looks like on the OP's vehicle. I do not believe that all this black death is caused by the foam melting.
Mike T.
 

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That gunk is a combination of congealed combustion gasses and melted injector noise dampening foam. Please for the love of god get that sorted out and cleaned. A lot of people ignore it because "its working fine" or "its not leaking."

If you want to do it yourself, there's a great video tutorial on it here:
 

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yep foam just make things worse when melting on cylinder head, but eventually black tar is coming from cylinder alone... (imagine that black smoke from exhaust just concentrates) :)

like said cold tar can be chipped carefully, then run engine HOT when removing the injector. In worst case a slide hammer is needed.

Air intake cleaner was a good solvent
 

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That gunk is a combination of congealed combustion gasses and melted injector noise dampening foam. Please for the love of god get that sorted out and cleaned. A lot of people ignore it because "its working fine" or "its not leaking."

If you want to do it yourself, there's a great video tutorial on it here: https://www.youtube.com/watch?v=zEp4GjcXy3o
Very informative vid, much thanks Rossafuss
 

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Discussion Starter #9
Thanks guys, I've been silent, because, as most of you suggested, I was reading, reading and reading... :) ... and stocking up on the right tools. Everything's supposed to arrive tonight. Any thought on whether or not I should need to replace the affected injector, or can I keep the original? What's the best way to verify?
 

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Testing electronic injectors is not easy, but leaky seal doesn't make injector bad.
What's the mileage? At high mileage it is good idea to have tips replaced.
We did have topic about it somewhere.
 

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I just did this job on my dad's 05 E320 CDI. It was a massive pain in the butt.
Please take my advice:
  • The injector is likely fine, just be very careful removing and reinstalling everything.
  • Do not disassemble the top of the injector, you will very likely lose parts and have to buy a new injector ($400).
  • Be very careful to clean the threads (where the bolt goes) and use a new bolt (its a stretch bolt)
  • Be very careful to clean the copper washer surface down at the bottom of the injector hole, so the washer seats cleanly. Always use a new copper washer, it has tiny finger that hold onto the injector tip, and once you remove it it wont stay anymore and you should pop another new one on.
  • Make sure you clean all the black crap up. Don't leave any remaining.
  • When torquing the bolt down, I believe its 7Nm and then 90-degrees. NOT what a forum page said which was 90-degrees and then another 90-degrees.
We followed bad forum advice elsewhere and torqued the bolt too tight which ripped the threads out of the head on the 2nd 90 degrees... bought a helicoil/timesert kit to repair the threads and finally got it all back together... then realized we had lost some tiny parts from the injector and had to buy a new injector. What was supposed to be a $40 job turned into a $600+ job... should have just taken it to the dealership in the first place
 

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should have just taken it to the dealership in the first place
do you have any idea how much that job would cost at the dealership? AT LEAST a grand....... lol
 

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Discussion Starter #13
The mileage is 250K miles. Just removed the injector. It wasn't a big pain. I carefully scraped off as much gunk as i could by a flat screw driver. Then, like most recommended, heated the engine up to work temperature. Sprayed ample with Gumout carb/choke cleaner around the #5. The bolt gave way right off. Wiggled the fork and it came off too. I then used CTA 1094 injector puller, a few knocks on the hammer, about a minute or so, and I had the injector in my hands... It was all gunked up. Again, the gumout did a great job. Overall it took maybe between 20-30 minutes to pull the injector out. Cleaned up the injector surroundings, the seat and the bolt wholes with IPA 8090B cleaning set, worked wonders, like people show on YT videos.

Question. Is the bottom of the injector seat supposed to be reamed? If so, does anyone know the size of the reamer tip? Flat or angled? I got me a generic diesel injector seat cutter tool set (pictured). Wondering if anyone had experience with those. Or should I even bother?
 

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Don't use generic cutter tools on MB. That might make you sorry very fast and on big scale.
Ross did deal with those injectors a lot (from what I read), so wait for his contribution, or search for his old topics.
 

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Discussion Starter #15
  • When torquing the bolt down, I believe its 7Nm and then 90-degrees. NOT what a forum page said which was 90-degrees and then another 90-degrees.
We followed bad forum advice elsewhere and torqued the bolt too tight which ripped the threads out of the head on the 2nd 90 degrees... bought a helicoil/timesert kit to repair the threads and finally got it all back together... then realized we had lost some tiny parts from the injector and had to buy a new injector.
Sorry to hear. I'm glad for you it worked in the end.

Meanwhile, according to the attached MB WIS the bolt should indeed be torqued at 7Nm, then twice the 90 degree. May I venture that your torque wrench went overboard with too much force?
 

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It is hard to tell from this picture.
If you have hard time to get a reamer, I would give it a go.
All you have to loose is couple of bucks for new washer and new bolt, while added time will add to experience.
 

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Sorry to hear. I'm glad for you it worked in the end.

Meanwhile, according to the attached MB WIS the bolt should indeed be torqued at 7Nm, then twice the 90 degree. May I venture that your torque wrench went overboard with too much force?
Just give it one 90 degree turn. My indie just hanged my injector seals this week. My number 1 injector was seeping. Somewhere either on this site or the other MB site they said to only do the one 90 degree turn. My indie confirmed this.
 

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7Nm + 90deg was old instruction, they added 2nd 90 deg later.

If there is no sign of wear on bottom surface (your looks good for me), just put injector in. Double check that bottom of thread hole is clean too.

Edit: Did you have new injector? Slide hammering may sometimes cause damage to old injector...
 

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Discussion Starter #20
I've picked up 2 used low-mileage injectors off of eBay just in case. But the original all look good to me. Is there a way to tell if any one injector needs to be replaced? I slide-hammered all 6 using the claw method. All 6 gave way in under 1 minute without major force, including the BD'ed #5; the slots on barrels look intact, so I would assume no damage from hammering.
 
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