I pulled my #2 injector because it seems to be the bad hole and the sealing ring (new last week) was burnt through between the crush portion (where the injector nozzle shoots through) and the sealing portion (where the injector seats) on the ring!!!!!!!!!!

WTFO is going on here? I just finished a 550 mile trip to the Bay Area.

Any ideas, I'm thinking injection pump. If the timing was out on this cylinder or if the pump is not edlivering fuel to this cyclinder in sufficient quantity then it would run lean and theoretically hot.
Could it be a bad prechamber or injector seat within the prechamber?

Anyone had this happen before???

here is the pic of the ring.

Attached Thumbnails

 

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'99 S420 - Mommies
'72 280SE 4.5 - looking to breathe life into it
'84 300SD Grey - Sold
'85 300SD Silver - Sold
'78 Ski Nautique

Have you pulled your other injectors to compare to this one since that 500 mile trip ?

Things should never get that hot there. Looks like a dirty seat (and leakage) when it was installed or it was never properly tightened.

I have not pulled them since the trip home. that's tomorrow's project.

the seat might have been a little dirty but you have to also understand that these new rings are only 7.5 mm whereas the orifice into the prechamber on this car is the old 10mm. Therefore you have a small amount of sealing ring hanging out in space. The actual seal I think is the heavier outer surface of the ring that injector tightens to.

I know these were set correctly torque wise so I'm actually considering that my IP is not delivering full fuel to this hole so it gets hot... Either that or there is a malformity in the seat.

Greg,
I got your PM and that might work to check it out. Might be one problem though as the seats are actually slightly beveled so it might be tough to fnd the right spot.

I've got access to a 79 that I can pull a prechamber from but I don't have the "special" tools. Anyone want to loan me theirs?

I hate to pay 60.00 for tools that I use once in my life... I'll even send a check as security.

I'll shoot an update tomorrow after I pull this injector to see what the new one looks like. I think I am going to trade out pumps tomorrow and see if this solves my slight miss and by default this issue. Wish me luck!!!

__________________
'99 S420 - Mommies
'72 280SE 4.5 - looking to breathe life into it
'84 300SD Grey - Sold
'85 300SD Silver - Sold
'78 Ski Nautique

Fisherman

My guess here FWIW is the new sealing ring you fitted was a reject. From the regular shape of the hole it looks as if the counter bore was too deep leaving the wall there paper-thin. That thin segment would get red hot and curl up even at normal EGT's. You would not have noticed when you fitted it.

The seal ring in your Pic appears to be the old type, hardened with 6mm Dia. hole. These were later superceded by (seal-injector/617 - Pt.No.64760331) for all 616 and 617 engines. The new ones have a 10mm hole, are left soft and are 0.5mm smaller on the OD.

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Beagle

Bad injector, it sprays sideways. Get them checked, they will burn the prechamber out, too.

Make sure they are correct side up, too, they leak if upside down. Ditto if there is also an old fit in the hole type seal in there too!

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

I was wondering if maybe it could be just a bad ring.

I had all 5 injectors tested and they were given a green light by the tech doing the testing. So I think it was okay.

Beagle,
I was told that this ring is the "new" one by both Mercedes and Fastlane. The old 10mm ring was replaced with this 7.5mm supposedly. My opening in the prechamber is 10mm so whatever metal is inside this is just hanging out so the seal that can be made to the injector around the pintle is minimal at best due to teh fact that the crush ring is not being crushed against the prechamber seat. I thought this odd but will look into it further.

__________________
'99 S420 - Mommies
'72 280SE 4.5 - looking to breathe life into it
'84 300SD Grey - Sold
'85 300SD Silver - Sold
'78 Ski Nautique

Fisherman

Just to clarify - are you fitting the seal with the raised rim in the counterbore sitting on the nozzle face and the angled face against the prechamber seat? This is the correct way - it is designed to crush against the nozzle face to prevent gasses getting inside the injector.

The seal ring was redesigned in 1981. At the same time the SD 220 nozzle was superceded by the SD240/.

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Beagle

Yhat is how they are installed. The counterbore is cut such that the injector face seats below or inside the outer ring... The beveled side of the ring is positioned to seat with the prechamber.

An update on this weekends projects...
I pulled my IP and replaced with a MW style pump from a 1979 300. I did this BTW without removing the oil filter housing...

This did not fix my problem os the slight miss. Seems that it is a "nailing" condition thatnow is causing me to want to shoot it but I willjust keep after these things one at a time.
Next is to check the prechamber seats for wear.

__________________
'99 S420 - Mommies
'72 280SE 4.5 - looking to breathe life into it
'84 300SD Grey - Sold
'85 300SD Silver - Sold
'78 Ski Nautique

You mention a nailing problem, bad enough you want to shoot it. I recall working through some strange noises last year on mine. They turned out to be some real bad valve springs. However one of the bits I picked up from a very experienced MB tech, was that the prechambers will on occasion get loose in the head and make a racket that sound a lot like nailing.
Since you are having troubles there I thought I might add to the mix here a little. BTW the tech said the best way to check that is just to torque them to specs. And that requires a special tool.
Just can't win I guess...

Hmmmmm, well maybe that could be a hint as to why this thing is doing what it is doing.
I need to take it in and have the local independant do an oil change and check out and maybe he will have some ideas too.
Thanks deis...!

__________________
'99 S420 - Mommies
'72 280SE 4.5 - looking to breathe life into it
'84 300SD Grey - Sold
'85 300SD Silver - Sold
'78 Ski Nautique

Old Deis,
You got me thinking and since i have saved all the rings that I have replaced over the past few weeks I decided to go check them all out. The first one out of the number 2 cylinder looked a little diferent than the rest when I first pulled it.

Guess what? The original 10mm ring looked funny but I did not really notice it that much since the holes are bigger than the new rings.
When I overlay the burnt ring in the photo here it matches the old one perfectly. It was burnt also in the exact same pattern!
You can see the slight difference between it and the other cylinders in this earlier thread. Note the difference in #2.

I am soooooo very happy!

There must be something wrong with that prechamber. In my compression test that cylinder was just as good as the rest so that is all I can think that would be different and since I put in this new (old) pump and I still have the same symptom now I can chase this issue and see if that fixes things.

Thank you for the note as I was just about resigned to live with this little miss (although it would drive me crazy forever).

God, I love this board!!!

__________________
'99 S420 - Mommies
'72 280SE 4.5 - looking to breathe life into it
'84 300SD Grey - Sold
'85 300SD Silver - Sold
'78 Ski Nautique

I have the same problem... looked at my sealrings this morning and my #1 looked like your #2
(OK.. that sounded funny) ........: ) your #2 cylinder ring.
mine was worn way out and I have good compression.. I am thinking pre- chamber problemo.. being new I'm not sure what the pre chamber does but mine is very sooty. I will follow your post, very similar problem this 240D

bennett

This is one of those deals where there is a big difference in the compression test and a leak down test..
The compression pulses happen so fast that this size opening is not likely to show up on your guage... ( it being so small that you would not go looking for something,, as compared to just thinking your engine is gradually losing compression, which is normal ) .....

But a leak down test might really show up this if it is a burn through...and also... since a leak down test is way quieter when happening you might actually hear the air escaping at the injector.

I am really pleased that more attention looks like it will be focused on the precombustion chambers.. I think this is a really neglected area of what should be regular maintenance... or at least something sooner looked at when certain symptoms are encountered....particularly poor fuel mileage.
HUUURRRAAAYYYY !