'05 CDI injector "Black Death" adventure - PeachParts Mercedes-Benz Forum

ROLLGUY · #1 02-10-2017, 01:07 AM

A couple weeks ago I purchased an '05 CDI from a dealer in Ohio (I am in CA). I asked them to take photos of the top of the engine with the plastic cover off. Much to their surprise and mine, it had a major case of the Black Death. Knowing this, they decided to wholesale the car. I made an offer that was probably more than they would have gotten at auction, and after doing the "dance" (back and forth negotiations), they accepted my offer. I got a good enough deal (even considering shipping costs) that even if I had to buy injectors or other expensive parts, I would still be ahead. The body and interior of the car is about a 9 out of 10. It seemed to be very well cared for.
So that brings me to today, when I decided to tackle the job of replacing the injector seals. Armed with the needed parts (purchased from Pelican), the reading of several injector threads, and viewing a few youtube videos, I was ready for the task. I have never touched a CDI engine before today, and have only seen photos and videos of the procedure. This one is probably one of the worst cases I have seen, but I knew what I was in for from the start.

After removing the plastic engine cover, I started picking at the black carbon, and breaking off large chunks. Every once in a while I vacuumed up as much as I could. I used compressed air to blow away the smaller particles.

ROLLGUY · #2 02-10-2017, 01:35 AM

After getting as much as I could by picking, vacuuming, and blowing, I went to the coin-op car wash to clean it as best I could. Knowing that if combustion gasses are escaping, I did not want to use high pressure water around the injectors without the engine running. Leaving the engine running, I sprayed the top of the engine with my favorite degreaser and pressure washed the engine. It did a pretty good job. I was also able to see the worst injector (#4), as the water pooling around the injector was being squirted out. I let the car continue to run when I got home, so I could blow off any remaining water so it would not drain into the cylinder. I started from the front and removed the injector clamp bolt using just the T40 bit from my 3/8 drive socket. I inserted it into an 8mm socket. It worked great. I then cleaned out the clamp bolt threads in the head using air, spray carb cleaner, and different pick type tools. I then used cotton swabs to clean out the carbon that the carb cleaner loosened up. Most of the threads suggested to chase the threads with a long tap, but I found my method to work just fine. After removing the injector, I cleaned the bore with a rag wrapped around a screwdriver. I used the female end of a long 1/4 drive extension wrapped with a rag to clean the seat. With the bore and injector clean, a new seal is inserted in the hole (I tried putting the seal on the injector, but it would not stay), and the injector smeared with ceramic paste......Rich

jay_bob · #3 02-10-2017, 05:56 AM

I would be careful doing that, the injector wires have several thousand volts on them. The CDI injectors are piezoelectric and rely on a high voltage pulse to vibrate a ceramic crystal. The reverse of a gas grill igniter.

ROLLGUY · #4 02-10-2017, 10:39 AM

The worst injector was #4, so I saved it for last. The other five were fairly easy, and no major force was needed to remove those injectors. At first I tried rotating the injector a little using a screwdriver between the clamp and the valve cover, but it would not budge. I figured I would need to make a tool to pull the injector. I have two slide hammers, a small H F unit and a larger-better quality one. I only had one tool for the small one, so I decided to modify it by welding part of one of the old injector clamps to it. I found that the small weight of the slide was not sufficient to even budge the injector the slightest bit. I sprayed liberal amounts of PB Blaster in the well around the injector and let it sit while I figured out how to modify the tool to work with my larger slide hammer. I had to use a bunch of different tools to accomplish this, and it actually worked. I did have to slide the weight about 50 times to get the injector loose. Man, that was a workout!

Since I broke one of the return line fittings, I could not get the car running. I called Pelican, and found out that the entire assembly with the fittings and hose is the only way it is sold, and at a cost of $125. Since I only needed one fitting, I went looking for another source. I found a seller on ebay motors that had a kit for the 4 cyl CDI for only about $18. I ordered it up, and it should be here in a few days. All things considered, it was not a hard job.......Rich

EDIT: I wanted to post the photos in the thread, but they were too large. I would like to know how to post them in a reasonable size.

ROLLGUY · #5 02-10-2017, 11:12 AM

The finished product (withe the exception of the return lines):

Bigdaddybenz · #6 02-12-2017, 08:04 AM

What would you say were the total labor hours to repair, and the total cost?

btw, GREAT JOB.... I also weld so I modify just about anything made of metal

ROLLGUY · #7 02-12-2017, 10:14 AM

Quote:

Originally Posted by Bigdaddybenz

What would you say were the total labor hours to repair, and the total cost?

btw, GREAT JOB.... I also weld so I modify just about anything made of metal

It took about six hours total. The parts were about $150 total. I imagine the cost at a dealer would be upwards of $1,500 for the same job.

spock505 · #8 02-12-2017, 10:18 AM

How come it's left to build up like that, would it not be spotted during service intervals?

ROLLGUY · #9 02-12-2017, 10:25 AM

Quote:

Originally Posted by spock505

How come it's left to build up like that, would it not be spotted during service intervals?

The cover must not have been removed, otherwise it might have been addressed sooner. The car ran great in that condition, so there must have been no reason to look for the problem. Knowing this ahead of time, I have had three potential CDI's looked at under the cover by the seller. If I plan to buy another one, this will be the first place I look. I am not afraid of this condition, and I am able to repair it. It is a good way to get a great deal on an otherwise excellent condition car.

spock505 · #10 02-12-2017, 10:32 AM

Quote:

Originally Posted by ROLLGUY

The cover must not have been removed, otherwise it might have been addressed sooner. The car ran great in that condition, so there must have been no reason to look for the problem. Knowing this ahead of time, I have had three potential CDI's looked at under the cover by the seller. If I plan to buy another one, this will be the first place I look. I am not afraid of this condition, and I am able to repair it. It is a good way to get a great deal on an otherwise excellent condition car.

Yup, great move on the negotiation front, bet the dealer thought something major wrong seeing that lot.

That said, i can't quite figure out how or what causes it, on the OM606's EGR build up in the manifold is common, but this from bad injector seals?

funola · #11 02-12-2017, 11:23 AM

Isn't there some sort of molded thick foam for sound insulation over the injectors? Fuel from leaking injectors melts the foam + heat = precursor to rock hard diamond. Light a match to the crud, if it smells plasticky, it is melted foam.

sloride · #12 02-12-2017, 12:22 PM

Quote:

Originally Posted by spock505

How come it's left to build up like that, would it not be spotted during service intervals?

That may have been paid for at the stealership by previous owner, never done the oil changer.

RunningTooHot · #13 02-12-2017, 01:15 PM

Thanks for documenting the deep-dive down the rabbit hole of "black death". (Perhaps this form of 'death' isn't to be feared as much as previously thought?) Job well done, and much appreciated!

I've been chomping on the bit about getting a CDI for the last few years. "Black Death" being one of my primary concerns. This helps allay those concerns and may just push me to further rationalize my "need" for another car. (Which I need like I need another hole in my head.)

One question:
Did you closely inspect the conical seal face for any evidence of erosion from the escaping gasses? IIRC, re-facing the seats is sometimes required. IF you had run up against that, what was going to be your plan of attack?

Thanks RollGuy!

chronometers · #14 02-12-2017, 01:29 PM

Since reading about black death here, I had the dealer carefully ck. the car I was buying before I paid for it and now check under the plastic cover and foam every time I change the oil. So far no problems.

Definitely want to ID this before it becomes a major clean up.

ROLLGUY · #15 02-12-2017, 05:39 PM

Quote:

Originally Posted by funola

Isn't there some sort of molded thick foam for sound insulation over the injectors? Fuel from leaking injectors melts the foam + heat = precursor to rock hard diamond. Light a match to the crud, if it smells plasticky, it is melted foam.

Yes there is supposed to be, but it was not there on this car.