The forward fuel injector is leaking around the threads. They were replaced with new ones a few months back, the mech said they had a different type of washer than he's ever seen before (dont know if thats the old or new ones). I have a noticable decrement in running and fuel economy. He just tried to fix it and said the piece where it threads into the prechamber is no good and must be replaced. He doesnt have the tools and said that usually head machining shops have to do it and that it is a copper part that is very difficult to remove/replace.

His english is not perfect so I have to fill in some places.

Anybody ever heard of similar? Can this be done in-place or will it require head removal?

The "washer" is presumably the heat shield. There's two types generally, the 10.00mm and the 7.5mm. The OM 617.9XX and OM616.9XX takes the former, although folks have reported using the 7.5mm.

The injector threads into the prechamber which can be removed from the head with the head installed. No need to pull the head.

Sixto
83 300SD
98 E320 wagon

I think he means the prechamber has issues and needs to be replaced. Yes special tools are required to remove them. A splined socket to unscrew them and a fitting screwed into the injector socket connected to a slide hammer to remove them. Reassembly may require a new seal ring and servicing the seat depending on which engine you are talking about.

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92 e300d2.5t
01 e320
05 cdi
85 chev c10

We need to know what year and model Mercedes you have? Or if you know what Engine you have.

If you have a 1982 W123 the Injector actually screws into the prechamer retaining ring. However, that is not usually where the injectors leak.

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84 300D, 82 Volvo 244Gl Diesel

The red arrows point at the possible leak areas.

The Injector can leak where the little nipples are pressed into the top of the Injectors.

If the parts inside of the Injector are not lapped well or assembled with dirt inside it can leak between the bottom Injector Nut and the upper Injector body.

The Injector Body can have a hairline crack and that will also leak out between the upper and lower half of the Injector.

The heat shields can either have a 5mm or 10mm hole in them. You can user either one of the heat shields.

Attached Thumbnails

     

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84 300D, 82 Volvo 244Gl Diesel

79 240d

OM616? (79 240d)

This sounds fairly close to what he was trying to explain, although he did mention a copper crush part. I will observe it to see if I can locate more precisely where its leaking, I assume he did also and concluded its not the injector itself. What type of shop would do this work? A head/valve machine shop? A diesel truck shop?

No copper there, only steel.

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Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC

In the older Mercedes Engines and and a whole lot of other diesel engines there is indeed a copper (or aluminum) copper crush washer that seals the injector like the heat shield does.

I suspect that the Mechinic has limited experience with your year and model Mercedes.

I forgot to mention there is at least one company that makes the stee heat shields and they are plated sort of a copperish brass color.

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84 300D, 82 Volvo 244Gl Diesel

Does that apply to this car?

Back to the original problem. In my experience, it's very common for some bubbling to occur if there is fuel spilled at the base of the injector. Some of offered that this is simply engine vibration that appears to be bubbles, others that the heat shield seal is faulty, and still others that the pre-chamber seal is the issue.

The first step is to make sure that fuel is not leaking from the steel injector line / fitting at the top of the injector, from either of the cloth-covered rubber fuel return lines, or from between the halves of the injector body (also called the injector nozzle holder).

Use brake cleaner to clean off all the fuel, and blow off with compressed air to get a perfectly dry situation, and then go for a test drive for a few minutes.

Feel the fuel return lines with your fingers, and if they are damp with fuel, they need to all be replaced. These rubber lines do age and require replacement periodically. Bulk hose in 1 meter lengths is usually the best value, cut into pieces about 18cm long for the lengths between each injector, about 21cm long for the last piece from injector #1 to the fuel filter mount. Don't forget the little end piece with the steel plug in it on the last injector by the firewall.

When you have the return line off, check the nipples for any deep scoring, which will lead to a permanent leak. Generally a new injector will be required, I don't think the nipples can be replaced by DIY.

The steel line fitting should be checked, try opening and closing it to make sure it is well seated. This is a low torque fitting, 25Nm, be careful you don't over torque too much. You may need to remove the line and inspect the end of the line (sealing cone) and the line itself to be free of damage and not cracked. Failure to keep all the steel line support brackets and clamps in place will lead to cracks / holes in the lines from the vibration.

If the two halves of the injector body are leaking, it will need to be taken apart and the sealing surfaces lapped until perfectly flat (2000 grit or higher wet sandpaper on a piece of glass) and free of defects, and then put back together.

If none of the above are the issue, then consider replacing the heat shield under the injector (these are one-time-use and should be replaced with new each time the injector is removed) and make sure it is torqued correctly.

If you still have a problem with leaks from the base of the injector / pre-chamber, I'd try to live with it if possible. Pulling a pre-chamber and the associated hassle of getting a good seal between pre-chamber and head requires special tools, and it has to be properly shimmed so the pre-chamber tip doesn't contact the top of the piston.

__________________
Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC

The 1979 Diesel Engine use the steel heat shields.

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84 300D, 82 Volvo 244Gl Diesel

Thanks everybody. The mech said he tried to seal it by "other" means but didnt know of it would hold.
I did the brakleen thing, clean and dry, and ran the motor, let it get warm and varied the throttle. No visible leaking going on from the injector or base. However, the valve cover gasket did have an oil leak *after* engine shutdown, which ran down to the base of the injector.
That leaves me with:
A. it never was a leaking injector/prechamber bushing and the mech was mistaken (unlikely as he is an older MB mech from the old country).
B. it was leaking, along with the valve cover and he did stop the injector/prechamber bushing leak (for now).