In march of '03 after returning from a 70 mile trip at 75MPH /100*C (Engine temp.) my engine started nailing. After some testing, I discovered that is is the #1 cylinder only. Its loud and clear between 700RPM and 3500RPM at all loads.

To try to fix this I have done several things:

1: Valve lash adjustment. No change, runs smother and more powerful.
2: Replace injectors with remanufactured models. Again, no change, smother running, more power.
3: Replaced cam woodruf key with 4*offset. Same results as above.
4: Adjusted IP injection timing. Again, same results.

The nailing is still there, just louder and more clear metalic. Does this mean its and internal problem with the IP? Should I bring it to a diesel shop and have them calibrate it on a IP bench, have it rebuilt, or replace it with a new/remanufactured one?

Could it also be a psyical mechanical problem with the engine as well?

I haven't had any problem with it other than the bad sound. I thank you all in advance for the help you have given on this and all my other posts!

Well if it were constantly nailing I would think it could do damage. My first guess was the IP being advanced to far, but being it was doing the same when it was retarded 4* I can't imagine it being that. What cetane fuel do you run? Any cetane boosting additives?

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Jeff M.
Mercedes W123 DIY pages are now located here.
1983 / 1984 300D Sold
2000 CLK430 Cabriolet ~58k Sold
2005 Avalanche 4x4 ~66k

The fuel prices are very close here. I have tried Texaco, Phillips66, Murphy's (Wal-Mart), and Get-n-Go. None had the cetane rating posted and all the people gave me a "you must be insane to think I know that" look. All except Texaco felt and ran the same. Texaco had less power and some smoke production. I use Power Service fuel supplement, 0.32Oz/gallon.

Could the 1-1/2hour of 100*C running caused the oil to be too hot for the IP? Befor I took the trip it ran well with no adverse sounds at all. It did have MUCH less power than it does now.

I know that look all to well. That is supposed to be a decent additive so it probably boosts it up 3-5pts which would put it at the very least of 43 which shouldn't create problems. 100*C isn't really that hot, it shouldn't have given you any problems because of it. Did you try to loosen the line and see if it stopped? How about swapping the injector to another cylinder. Were the injectors flow calibrated?

__________________
Jeff M.
Mercedes W123 DIY pages are now located here.
1983 / 1984 300D Sold
2000 CLK430 Cabriolet ~58k Sold
2005 Avalanche 4x4 ~66k

That's how I found out that #1 is nailing. I "cracked" open the line to the injector and the noise stoped. Its not the injector itsself, I just replaced all 5 after it started nailing. I don't know if they were flow calibrated or not, they came in their own stock boxes.

It is possible to get a bad rebuilt injector, and the chances of you unfortunately putting it right into #1 where you had the problem before are not astronomical - 20%?

So the cheap thing to do as a test is swap the injector from #1 with another injector already in the vehicle, say, #2 or #3 or whatever is easiest to get to.

In doing that you fairly conclusively eliminate an injector as the problem.

On the other hand, for all I know, your car is doing on one cylinder what mine does on all five.

Ken300D

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1982 300D at 351K miles
1984 300SD at 217K miles
1987 300D at 370K miles

#5 runs quiet so I swapped #1 and #5 injectors. Nailing stayed with the #1 cylinder. No change in the sound or performance.

82-300TD,

Did you check the ball pin inside the pre-chamber?

P E H

BoostnBenz,

FYI: putting an offset woodruff key in the cam sprocket does not change the timing of the injection pump. If the cam is 4 degrees late from timing chain elongation, the IP will be only about 2 degrees late because it is closer to the crankshaft sprocket.

P E H

Check PE Haiges suggestion and make sure that the prechamber is still intact. That is your last cheap alternative. If the prechamber is still good, then you need to break out the "stethoscope" (in my case a 3 foot long 3/8" extension), and start listening for the exact source of the "nailing" sound. You may very well have a cracked piston, or spun bearing. Both of these will result in catastrophic failure in short order if not taken care of. Up high will likely be the piston itself, and down low will be the bearings.

They should be the same. The cam/IP sprockets are the same diameter an the crank is 1/2 the diameter. If the Cam shows 4* off the IP will be 4* as well. If your suggestion were true, when you put in a new chain, the IP timing would be wrong.

What is the ball pin look like? What should I be looking for in a good prechamber?
If it is a spun bearing, would it be in the piston, crank, or another object? I have done some in-chassis bearing roll-in's before so that might no be to bad. If it is the piston, what cost hit could I be looking at to fix this at a shop?

As I have said long ago, I aim to never see my car in a shop as long as I own it.

Indeed PEH, that is why I figured I'd kill two birds with one stone and just change my chain. 82-300td said he adjusted the IP, he also said how to in another thread, so I didn't mention it. Sorry to imply this to anyone reading. I wasn't aware the IP was off half the cam gear's amount though.

Amen to that. Neither of my current vehicles have been touched by a mechanic as long as I've owned them (3+yrs on the talon), but for the past 14months or so I've been mechanic free for everything I've owned. When I need new tires they get the rim assembly brought in the back of a vehicle with no center caps, I stand there the whole time as they put the new tires on or balance them. I carry it to them and back to the vehicle I'm carrying them in.

__________________
Jeff M.
Mercedes W123 DIY pages are now located here.
1983 / 1984 300D Sold
2000 CLK430 Cabriolet ~58k Sold
2005 Avalanche 4x4 ~66k

I've read some stuff on nailing before, and I just bought an '85 300 TD so now it applies to me, too!

What is nailing, and how do I recognize the sound? I don't think I have it - it just sounds like a diesel right now - but I would like to know what to look out for.

Thanks!
kma

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74 Porsche 914 2.0 - 92k and counting
85 300 TD - 263k and counting
83 300 TD - 190k and counting
74 Harley Davidson Superglide - 38k and counting
68 Harley Davidson Sportster - currently in kit form

82-300dt,

The reason the IP will be 1/2 as many degrees late as the cam, if the late timing is caused by elongation of the timing chain, is because the IP is only about half as far from the crankshaft sprocket as the camshaft sprocket is.

The timing chain wears so much for each pin/hole combination. So if it elongates 1 mm from the crank sprocket to the IP sprocket and it causes the IP to be 2 degrees late, there will be 2 mm elongation from the crank sprocket to the cam sprocket which would make the cam 4 degrees late. These numbers are just examples as I have no idea how much elongation causes so many degrees timing error.

The cam timing can be corrected by an offset woodruff key and the IP timing can be corrected by rotating the IP. If you put an offset woodruff key in the camsprocket, it will have no effect on the timing of the IP. In the above example, a offset woodruff key in the cam sprocket would make the cam zero degrees late but the IP would still be 2 degrees late. A new timing chain will be bring the timing back to original (if the IP was never moved and the head was not planed) except for the wear on the sprockets.

Here's another example. Take a rubber band and cut so it is one single strand 2 inches long. Put a mark in the middle of the single strand. Place the single rubber strand on a ruler and stretch one end of the single rubber strand 2 inches. Notice the center mark moves only one inch. The same goes for the elongation of a timing chain.

Understand?

P E H

kashbaugh, nailing sounds like metal hitting metal. In my case is as a loud clear and unmistakeable sound somewhat like a hammer or sledge quickly hitting a slab of solid concrete or a thick metal bar snaping in half (But not that terrible).

P.E. I understand now, you are right.

I have listned mor closely to the sound and is seems to come from the block/head meeting level, exactly where will have to wait until I can locate a sutible stehoscope to use.