Greetings,
I just took ownership of a nice, well cared for 300SD w/OM617a. I picked the car up after several viewings and discussions with the owner. It ran fine and performed very well on the 3 hour drive home on the interstate. The next day when I started it (cold) I noticed a bit of what i believe was injector nailing when the engine was heating up.
I adjusted the valve lash (several were very tight out of spec), did a diesel purge, and replaced both fuel filters. As another item, I blocked the EGR vacuum line.
Now, the engine starts and runs beautifully...except for a nailing/tapping noise now at 1500-1800 rpm while accelerating LIGHTLY. If I give it more pedal, the noise immediately dissipates. Regardless of load, it never happens above 2k rpm.
I thought..crap, I made it worse. I checked my valve lash again. All good. Went for a drive, same symptom. I removed the BB from the EGR vac line, this made it much better somehow, but the nailing is still there intermittently when accelerating lightly or cruising slowly. Other than the noise, the engine runs excellent. Plenty of power, smooth idle, hardly any smoke, etc.

Any suggestions of how to proceed with troubleshooting?

A friend says that these engines like to be run hard and I should troubleshoot with a little cetane booster and a heavier foot, but I'm not sure I buy into that yet...

Thanks in advance,
Matt

Injector + Heat shield + Nozzle, Prechamber + Collar, and Nailing. LINK THREAD

Warning ALL Diesel Owners, Random poor quality fuel

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1985 300SD
1983 300D
1984 190D
2003 Volvo V70
2002 Honda Civic

https://www.boldegoist.com/

Adding Cetane Booster will likely stop the nailing sound because it changes the burning rate of the Fuel.
About 2000 rpms is when the Turbocharger Boost starts to kick in and when the Boost reaches the ALDA that would be when the ALDA would give extra Fuel.

Hunter orginized the links to make things easier to find:
Repair Links
http://www.peachparts.com/shopforum/diy-links-parts-category/

http://www.peachparts.com/Wikka/DoItYourSelf

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84 300D, 82 Volvo 244Gl Diesel

Thank you very much for the links and advice. I forgot to mention the PO replaced the injectors, lines, and glow plugs about 15k miles ago (@ 200k).

After a 2 hour drive on the highway yesterday, it seems to drive much better today. Very little nailing but intermittently still there.

Is there a specific brand that everyone prefers as far as cetane boosters?

If you are not familiar with these Diesels, their normal sound can be falsely concerning. It's going to make some klickity klack even running 100% normally. Then again, there is a point where it is a concern but I see people chase noise issues and there is nothing abnormal. A video with good audio would help.

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1991 F250 super-cab 7.3 IDI. (rebuilt by me) Banks Sidewinder turbo, hydroboost brakes, new IP and injectors.
2003 S430 - 107K
1983 300SD - Tanoshii - mostly restored ~400K+.
1983 300SD - Good interior. Engine finally tamed ~250K.
Monark Nozzle Install Video - http://tinyurl.com/ptd2tge

The only comparison i have to go by is my 7.3L Powerstroke diesel in my F250. I will take a good quality video next time i go for a drive.
Thanks for the help guys!

On another note, I started it cold in the garage this morning and noticed a decent amount of soot under the exhaust outlet afterwards. I'm guessing this is a result of the crud being loosened from the diesel purge I did two days ago? Or simply normal for cold start?

The car should not be as loud as a PSD, close but those 7.3 strokes are LOUD! Well, at least the ones before they came out with split-shot injectors.

I wouldn't worry about the soot. It happens. You probably loosened some carbon up in the exhaust from your ride.

__________________
1991 F250 super-cab 7.3 IDI. (rebuilt by me) Banks Sidewinder turbo, hydroboost brakes, new IP and injectors.
2003 S430 - 107K
1983 300SD - Tanoshii - mostly restored ~400K+.
1983 300SD - Good interior. Engine finally tamed ~250K.
Monark Nozzle Install Video - http://tinyurl.com/ptd2tge

The engine (300SD) isn't loud at all! Actually very surprised. Obviously sounds like a diesel clatter, but inside with windows up at idle you can barely tell it's a diesel except for a slight vibration and faint sound. The nailing sound is audible in the cabin except with the fan on high.
But yeah the truck is pretty loud and clattery haha. Nice turbo whine as well.

Did it drive nice on regular Diesel or Diesel with Cetane Booster.

The may be one in the same products. I occasionaly use Power Service; Diesel Kleen from Walmart.

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84 300D, 82 Volvo 244Gl Diesel

Diesel911,
It runs great with diesel and normal amount I think 4 or 8 oz can't remember of Diesel Kleen in with the fill up - nothing else added. Only very intermittent nailing when cold and then VERY intermittently 1400-1600 rpm when accelerating or decelerating.
I think next fill up I will try a different fuel station and perhaps a different brand of booster + lubricant.

I mainly wanted to check if the nailing could hurt the engine as I was planning a road trip next week.

Here is a comparison video I did. It accounts mostly for motor mounts but you can see how quiet the second car in the video is. Both are 1983 300SDs.

http://www.youtube.com/watch?v=tHFhjbAg8MQ&list=UUX3YyyjeCyrrjETZIhZm95Q&feature=c4-overview

__________________
1991 F250 super-cab 7.3 IDI. (rebuilt by me) Banks Sidewinder turbo, hydroboost brakes, new IP and injectors.
2003 S430 - 107K
1983 300SD - Tanoshii - mostly restored ~400K+.
1983 300SD - Good interior. Engine finally tamed ~250K.
Monark Nozzle Install Video - http://tinyurl.com/ptd2tge

Update for all interested.
As stated, the car had Bosch injectors put in 15k miles ago.
I tried all troubleshooting steps listed above to no avail, still lots of intermittent nailing.

Rebuilt, tested, and balanced the injectors myself w/ Monark nozzles to 2010 psi +/- 20 psi and the engine now runs perfectly.

One of the Bosch injectors had a broken spring, and another had a broken nozzle tip and was popping at 1600 psi. The rest were between 1800 and 2050 psi.

So if you have Bosch injectors...replace with Monark nozzles!

It sounds like whoever rebuilt the Bosch injectors didn't know what they were doing.

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CENSORED due to not family friendly words

That could be, although the PO said they were "new". Could have been new, rebuilt...

Well, I guess this is a good lesson on not trusting what the PO says is new or replaced.

__________________
1991 F250 super-cab 7.3 IDI. (rebuilt by me) Banks Sidewinder turbo, hydroboost brakes, new IP and injectors.
2003 S430 - 107K
1983 300SD - Tanoshii - mostly restored ~400K+.
1983 300SD - Good interior. Engine finally tamed ~250K.
Monark Nozzle Install Video - http://tinyurl.com/ptd2tge