My 190DT (OM602.961) nails so I rebuild the injectors with Monark nozzles and balanced them thinking this would smooth it out. I was in the process of testing the motor (it still nails) and I noticed some bubbling coming from under the plastic injector shroud. I assumed it was coming from the crush washer but after pulling the injector and putting it back in without the shroud it looks like it is coming from around the injector seat.

Would the drop in compression on that cylinder cause the nailing?

I loosened the injector line on that cylinder the RPMS did drop so that cylinder is not dead.

The options as I see them.

1. Drive it. It runs fine, it just nails which is annoying.
2. Pull the heads and replace the injector seat?
3. Get a different head.

Thoughts?

1. Drive it. It runs fine, it just nails which is annoying.
2. Pull the heads and replace the injector seat?
3. Get a different head.

Thoughts?

Are a ONE TIME USE ONLY part.
(They do deform as the pressure of the Torque is applied to the Injector.)

'Could that explain your problem?

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'84 300SD sold
124.128

My main problem is that it looks like I have a leak around the injector seats which after further research is called the threaded ring and is complimentary to the prechamber. From the manual it looks like the prechamber threads into the head. The seal between the injector the threaded ring looks good but I can see "diesel bubbles" coming from interface between the threaded ring and the head when the motor is running. I don't think diesel is actually coming up through the treaded ring, but there was diesel on top of the threaded ring because I had just bled the injector lines before starting the motor.


My other problem is that the car nails.

Concerning the head shield, they look good, and if all they do is block heat and prevent debris from getting down around the injector why should I replace them?

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they, in addition to blocking heat to the injector, provide a seal to the combustion gasses. you should replace them because they only seal once.
they are a crush washer, and once installed, and torqued down, they do not seal well again.

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My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
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I understand the crush washers should be replaced. They are new.

The leak of combustion gasses around the prechamber and around the prechamber ring is a somewhat common issue with the 602 cylinder heads it seems. Usually people pull the injectors, the prechamber rings, the prechambers and clean the bores in the cylinder head and the reinstall according to the procedure in the FSM and that cures the problem. Most folks would never know if this sort of leak was occurring until the injector return lines fail and they have a circumstance with some fuel collecting around the base of the injector/prechamber.

If not the next step would be to re-cut the prechamber bore and then add a steel spacer for the prechamber to seal against. This procedure is accomplished easier with the cylinder head off the engine as the protrusion of the prechamber tip into the combustion chamber is critical.

Of course there can be issues with the cylinder head being cracked and leaking out through the prechamber bore but you really can't know that without removing the cylinder head and having it inspected and pressure tested.

The black plastic rings around the injector's base are really there to prevent debris and corrosion from getting into the splines of the inclined prechamber ring in my opinion; they do no sealing effect beyond that. These plastic rings have been discontinued and are no longer available from MB as a replacement part.

The most prudent course of action will be to pull the offending prechamber, clean things up and reinstall with the hope of getting it the seal up properly, this works for most people who try it.

Whether this issue is the cause of “nailing” or an effect of “nailing” I couldn’t say, the volume of the leaking gas is very, very small so I would tend to think it is not a cause. You should be able to move the injector from the offending cylinder swapping it with another and if the “nailing” follows the move, then the cause is the injector and if the issue does not follow change one has to assume it is either a combustion chamber issue or a fuel delivery issue specific to that cylinder. Before I did anything an $8 Lubro-Moly Diesel Purge douche would be worth doing to see if that affects anything. Good Luck!

Billybob,

Thanks for the info. Based on my compression test I think you are right about the volume of the gases coming out. That cycinder was not much lower lower than the others.

I don't think the nailing is from the injectors because I just rebuild them with Monark nozzles and balanced them to within 50psi of eachother.

I will run the purge and see what happens.

If it's just air in the lines, it will work itself out.

__________________

Gone to the dark side

- Jeff

babymog,

So you are saying that the nailing could be air working itself out of the lines?

Ran it around the block and though that would be enough.

I had to run mine fairly hard when I changed hard-lines before it smoothed out, I think that the bubbles can remain in the lines until there's enough flow and a very small bubble can be enough to change the injection timing.

__________________

Gone to the dark side

- Jeff

Strangely enough, and somewhat inexplicable, it may take 250 miles for all the air to completely disengage from the lines. Replacing the #6 line down in Raleigh caused the '86 to have an injector knock for 1/2 the return trip back to NY.

Aaah, patience Grasshopper.

I ordered the $50 dollar splined socket to tighten my prechamber down and I'm also going to get some Lubro Moly Purge and see how it does. Thanks for the input.

Can't new injectors nail for a little while until they break in? I noticed a little air leaking out of one of mine on the 2.5T as well after replacing an injector. I forgot all about it until now.

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What Would Rudolph Do?
1975 300D, 1975 240D, 1985 300SD, 1997 300D, 2005 E320 , 2006 Toyota Prius

The picturs you are showing are actually of 2 different types of setups.

The Colored Picture shows the Injector threading into the Prechamber itself. The Injectors for those have threads lower on the Nut and are M22x1.5 threads. The Prechamber Retaining Rings have serrations instead of slots.
In the black and white Drawing it is showing the Injector Threaded into the Prechamber Retaining Ring. Those Injectors have M24x2.0 threads and the Retaining rings have a Slot on each side.

Which one do you have?

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84 300D, 82 Volvo 244Gl Diesel

He mentioned the "splined socket" to tighten his pre-chambers, which indicates to me the inclinded-injection head where the injector holder threads into the pre-chamber.

__________________

Gone to the dark side

- Jeff