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What causes injector nailing

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I can not seem to diagnose what is causing my #1 cylinder injector to have a rather loud nailing noise. I was suspect of the injector itself so I switched it with the #4 injector and the nailing is the same still at #1.

When you loosen the fuel line at #1 the nailing goes away but of course you are now leaking fuel and skipping.

The nailing started a few months ago during a cylinder head gasket episode where the gasket was blown pouring oil into #1 cylinder. That has been corrected with the new head gasket and the car runs great except for the slight skipping and white smoke at cold start up that clears up after a couple minutes.

The nailing noise in #1 did not use to be there and I would like to know what causes this phenomenon and what can be done to clear it up?

Thanks, John

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Old problem coming back?

When you replaced the head gasket did you examine the surface where the sealing ring goes around #1 cylinder. Do you remember the picture of the erosion on the head that I e-mailed you before you did the job. Oil may be seeping into #1 regardless of the new gasket. Pictures available. Just a thought. Been there done that.

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Marshall Booth wrote:

You've already associated the noise with the location and NOT the injector. It could be the injection pump delivery valve or the condition of the prechamber. Does the noise remain as the engine speed increases and engine load increase?

It may be nothing more than a little carbon residue that broken away from the prechamber and may burn up after a few days. It could also signal that a prechamber has cracked and that (while VERY rare unless someone has used starter fluid) can result in the engine being destroyed - VERY suddenly.

Marshall

Marshall,
the noise goes away as the engine speed increases. It is only at idle. I wondered if it was carbon but it has been over 3 months now. I did visually examine the prechamber from the head side when it was removed and cleaned it. I did not notice any cracks but I really wasn't looking for this.

I am really wondering if the excess oil that cylinder was trying to burn caused this problem. Could the oil burning in that cylinder have caused the issue?

Joe,
I carefully examined the head surfaces and saw no erosion when I replaced the head gasket. The oil usage has been 0 since the repair. I am leaning towards the prechamber or delivery valve or glow plug issue...

Thanks

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Replacing all the o-rings, copper washers, and springs in the delivery valves is inexpensive.

Also, consider moving a delivery valve (like you did with injector) to see if the problem follows.

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Max Dillon
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'87 300TD, 334k miles (need to pull the head again...)
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Meade,
I changed the delivery valve and components out with #2 valve and it made no difference in #1 nailing noise at idle.

Also I pulled the #1 glow plug, cleaned and tested it OK. It had some soot but was not caked with carbon or anything else. Also I blew out the prechamber by turning the engine over without the glow plug and also used my air nozzle.

so I have come to this conclusion:

It is only at idle
It is not the injector
It is not the delivery valve
It is not the glowplug
The noise goes away when you loosen the fuel line

It must be something to do with the prechamber? Is it possible for one or more holes in the prechamber to be blocked causing the noise?

I have never pulled a prechamber but it might be the next step...

Thanks, John

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Have you tried a dose of Chevron Techron fuel injector cleaner or Lubro Moly Diesel Purge (run straight through vice adding to fuel tank)? I'd try that as next step before pulling a pre-chamber.

It could simply be a matter of carbon build up that needs to be burned out - may take thousands of miles to do that, if everything else is in proper working order.

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Max Dillon
Charleston SC
'87 300TD, 334k miles (need to pull the head again...)
'95 E300 Diesel, 335k miles (daily driving duty)
'73 Balboa 20

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Remove the injector line then remove the injector and heat shield and have a look inside the prechamber. Is the ballpin completely intact. I have seen the ballpin completely burned away on earlier diesels with the ball spinning around like the ball inside a police whistle! The prechamber can be pulled out pretty easily with several special tools.

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1993 300SD with '99 606 engine. 111,040 miles.
1994 S350   75,238 miles
1995 S350 148,124 miles.
1996 S420 with '99 606 engine  Sold
1999 S600  one of 14 imported  Sold 
1989 Bentley 8  Sold at 40,000 miles.

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I've done the Techron but not the purge. Is there a way to manually clean the inside of the pre chamber by going through the top with the injector pulled with a small wire brush or dental pick or something?

I don't want to have to acquire the pre chamber removal tools! $$$

Yes, its not the end of the world with this condition at idle but I guess I'm in pursuit of perfection.

Yes the purge I will try.. After that oil burning episode for a week or so it's bound to be carboned up in that #1 prechamber. I just hope it is not cracked as Marshall alluded to but its never seen starter fluid....

Thanks alot...
John

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jtripp wrote:
Remove the injector line then remove the injector and heat shield and have a look inside the prechamber. Is the ballpin completely intact. I have seen the ballpin completely burned away on earlier diesels with the ball spinning around like the ball inside a police whistle! The prechamber can be pulled out pretty easily with several special tools.

Thanks Joe, I just got your reply after I answered Meade... I will take a look at this. I know I have seen the ball pin through the hole but did not check as to the exact condition. I hope it is just carbon..
Thanks, John

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I've looked inside my prechamber when changing injectors, but don't know what I'm looking at, so could not identify the ball, which the manual specifically points to as a check of the prechamber. Can someone describe or provide a photo (difficult to do, I bet) of what the inside of the prechamber should look like.

A photo of a prechamber out of the head might be helpful, as well.

Thanks in advance.

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There are some pictures here of a OM617 taken apart, including the bottom of the head and the prechambers (from piston side)

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I found this pic of a prechamber for my SDL last night...
John

pre chamber.JPG
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Here is the cutaway drawing from the manual..
you can see the ball and pin in the drawings. It might be possible to get a small flexible wire brush in to the lower chamber and clean out and then blow out with air?...
John

pre chamber cutaway.jpg
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Thanks John,

If I pull the injector and look in the opening, should I see a pin with a round center (the ball) going across the opening at the bottom? Does the 617 look pretty much the same?

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Guy:
They are basically the same inside looking down from the top. Maybe some different angles machined on the bottom of the ballpin.

John:
Maybe you should take #2 injector out as well and compare the ballpins being that the problem is with #1 cylinder. Are you sure that your engine isn't oil pumping into #1 cylinder? The oil will be forced into the prechamber and may be the culprit.

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New York club member since 1976.

Continuous Mercedes ownership since 1964.

1993 300SD with '99 606 engine. 111,040 miles.
1994 S350   75,238 miles
1995 S350 148,124 miles.
1996 S420 with '99 606 engine  Sold
1999 S600  one of 14 imported  Sold 
1989 Bentley 8  Sold at 40,000 miles.

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Joe, I cringe to think that it might be pumping oil into #1 but am 99% sure it isn't. There is no oil smoke and it has used 0 oil (mobil1 diesel 15W40) since the head gasket change in November and its a daily driver for my wife 30 miles round trip.

This afternoon I pulled the injector and inspected the pre-chamber with a bright light and observed the "pin and ball" all intact and I used a very thin wire to probe and scrape the insides of it using some injector cleaner and air nozzle and it looked good and clean to me.

The noise is a mystery to me and I guess I am a little picky about it. The real mystery is that it goes away when you loosen the fuel line so it must have something to do with the combustion or delivery of fuel in that cylinder.

Thanks as usual,
John

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I've had a nailing cylendar, but only when stone cold. As soon as I'd been running for about a minute, the nailing stopped, although I would sometimes think I heard it intermittantly at speed and temperature.

Just recently, the nailing stopped, quite suddenly, after 15k mi. I had assumed it was injector related, as I had replaced all injectors for leaking, but never tried to diagnose it. I bought the car 15k miles ago, and the previous owner had been using a 75 deg. thermostat. I also switched to Mobil Delvac 1 7k miles ago, and the oil consumption has just now stablized to its previous burn rate, 1 qt/2k mi, after having increased drastically to 1 qt/600 mi. about 3k mi after I switched.

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I am having the very same

I am having the very same issue, but cyl 1 and 2 seem to both be nailing.

I have all rebuilt injectors and have moved the #1 injector with the noise staying with the cylinder. The ball seems ok also.

I was wondering if this had ever been resolved (been 5 years now though)

Same symptoms in terms of only at idle and then it goes away when revved. It is irritating and I'd really like to make it go away

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Low compression from partial

Low compression from partial hydrolock.

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