OM617 knocking - Page 2 - PeachParts Mercedes-Benz Forum

mannys9130 · #16 10-26-2015, 12:35 AM

Does it smoke at all?

Were the valves abnormally out of spec on #5?

Replacing with new rebuilt injectors did not affect the knock and moving the injectors did not move the knock to another cylinder?

This chuffing out of the exhaust is interesting... I'd get a hot compression test next.

83TD · #17 10-26-2015, 08:42 AM

Diesel 911 is correct, by "hanging up" they were referring to the needle valve not moving smoothly in the nozzle body.

It was an interesting dealership to visit--started out as a Studebaker dealership which I think picked up the MB line after MB bought Studebaker, if my aging memory is correct. Operated by an elderly couple in an old building in Owatonna, MN who were wonderful to talk to and deal with. Quite different from today's dealerships.

Peter

barry12345 · #18 10-26-2015, 10:24 AM

Quote:

Originally Posted by Tomas.brannholm

Hi Barry,
If I understand you correct I will use one glow plug for measuring temperature in the cylinders (1-5)?

I was checking the car today and when cold it is almost now knocking also the engine temperature is very stabile just above 175.
The turbo have new sealing's and bearings
I just give some more information about the condition of the car.

Thanks.

// Tomas

No, at first just do a general mili volt scan at the harness on all the existing glow plugs. Plus record them.This just to see if there is any indication of a substantial temperature difference with that cylinder.

Or at least enough to pursue and verify more accurately. Depending on the overall readings obtained this may give some indication. So easy a test it is ridiculous to pass it by.

Now if the readings are all over the place it just indicates the old plugs are way off in values to each other because of aging symptoms.

Personally I doubt it is the injection pump if the cars overall milage is correct. Combined with the strange chugging noise you detect. Now if that temperature is low in comparison might also be signifigant.

Using every tool possible to get some form of diagnosis in a systematic fashion is better than guessing. For example years ago someone might have over torqued the number five injector line at the injection pump this moving the element adjustment . An injection pumps aging will not advance the timing on one cylinder. Or in no way I can think of at least.

Some examples. Cylinders 1-5 read 5mv. 4.7mv 5.1mv 4.5mv and last at say 8mv.

Or if plugs have aged too much you might get. 6mv. 9mv. 4mv. 8.1 mv. 6.1mv.and 7mv for example.

In the second case it is obvious the charactaristics of the plugs have changed too much to be of any use for comparisons. While in the first case there is some indication to look a little more carefully by going to a better standard or using the same plug. .. To reject a preliminary test that takes so little time and is so simple to do is a persons choice. It is not my car.

What I did pick up initially was since your cold compression test indicated you have a good consistency of compression across the engine. Normally all cylinders should be running at about the same relative temperatures.

These engines are so well constructed if not overbuilt. Mechanical failure of the lower block engine components is not that common at your milage. Of course like anything it is still possible but just not that common.

To keep all the ducks in a row. Perhaps an expression not used in Europe. I am assuming that only diesel fuel was used in that engine to the best of your knowledge? One more seemingly strange question. You have carefully heard other diesel engines of this model running? I ask because I hear some strange background noises with them that I consider normal. Except the chugging sound you mention. All my 123 type diesel engines are in good condition. So I have always considered them just normal sounds of this design.

One more clue of why I am being a little more persistant than seems justified. Your mention of the pulse seemingly stronger or the vibration of the number five injector line seems stronger to you. It could be your imagination but if true it could also represent something .

Simply because when you feel the pulse it is also the approximate firing point of that cylinder.If it were more advanced for example could it be a premature harder ignition hit than the other cylinders you feel? I guess a pre ignition type of thing a possibility. With rebuilt injectors and fairly even compression in my opinion other than some possibility of vibration harmonics because of different lengths of the injector lines at best. All injector lines normally in my opinion should feel about the same. Although I have not thought previously about this much.

If you have read many of my posts I am for simple tests where possible. So I will give an even simpler test as well.

Run the engine on a can of vegetable oil. Waiting long enough to make sure the filters and base of the injection pump have some. If the noise is gone the probability of it being a mechanical cause is reduced but not totally eliminate. The vegetable oil flame front is softer and perhaps longer. Personally I prefer the milli volt test. It can give more valid and accurate information.

Tomas.brannholm · #19 10-26-2015, 01:48 PM

Quote:

Originally Posted by mannys9130

Does it smoke at all?

Were the valves abnormally out of spec on #5?

Replacing with new rebuilt injectors did not affect the knock and moving the injectors did not move the knock to another cylinder?

This chuffing out of the exhaust is interesting... I'd get a hot compression test next.

Hi,
No smoke and valves was almost perfect on all cylinders. No change when moving injectors or deliver valves, still problem with cylinder no 5.
I am think it is a bearing or piston.
I will check compression hot.

Compression hot
1 = 370
2 = 365
4 = 370
5 = 375
3 = 365

// Tomas

barry12345 · #20 10-26-2015, 09:50 PM

Tomas, when you are finished fixing or really know what it is please post the information. It helps others.

leathermang · #21 10-26-2015, 10:07 PM

Piston or crank are deep engine big jobs...
The tests which have been conducted like moving the injectors do not affect one major item between the injectors and the combustion chamber which can affect the efficiency of that combustion chamber...
That is the condition of the route the fuel takes between the injector and the top of the piston.... the holes in the pre combustion chamber..
He has ordered the tool for pulling and inspecting the those holes and we are hoping that is the problem....since it can be fixed easily ...

cooljjay · #22 10-26-2015, 11:15 PM

Anyone think, that maybe not timing the injection pump to the new chain could be the issue?

It would be interesting to know, if this issue was happening prior to the timing chain replacement....

I wonder if there could even be a key left to compensate for timing chain stretch in the cam....

I know a lot of folks, just roll in a new chain....with out any thought to if there were any keys install, injection pump timing nor replacing guides....I wonder if this could be echoing from something else...

I know people will pitch fork me for this....but it may be time to just drive it, till it dies.....then buy another or another engine...

As leather said, this really sounds like a deep engine issue, requiring some very deep digging on a engine stand....

leathermang · #23 10-26-2015, 11:21 PM

How would new chain and timing ONLY affect one piston...
I am hoping for the pcc being the problem...
They are small holes and critical for the proper dispersion of the fuel across the head of the piston....

cooljjay · #24 10-26-2015, 11:39 PM

Quote:

Originally Posted by leathermang

How would new chain and timing ONLY affect one piston...
I am hoping for the pcc being the problem...
They are small holes and critical for the proper dispersion of the fuel across the head of the piston....

No idea....Stranger things have been known to happen....

I can't figure out how the knocking could be the pcc....When the knocking is still there when the injector line is disconnected....Unless it is something echo'ing down the line, or something wrong deep in the engine...

Maybe a PO ran it out of oil, timing chain snapped, used head installed....who knows....Just would be interesting to know why the chain was replaced....something had to lead to that....Not like there is a highlighted sentence in the FSM that the timing chain expires at 100k....

mannys9130 · #25 10-27-2015, 04:21 AM

Quote:

Originally Posted by cooljjay

Anyone think, that maybe not timing the injection pump to the new chain could be the issue?

It would be interesting to know, if this issue was happening prior to the timing chain replacement....

I wonder if there could even be a key left to compensate for timing chain stretch in the cam....

I know a lot of folks, just roll in a new chain....with out any thought to if there were any keys install, injection pump timing nor replacing guides....I wonder if this could be echoing from something else...

I know people will pitch fork me for this....but it may be time to just drive it, till it dies.....then buy another or another engine...

As leather said, this really sounds like a deep engine issue, requiring some very deep digging on a engine stand....

He said he bought the car with the knock. Replaced timing chain, no change.

Timing on cam and IP are both dead on from the factory. The chains wears, timing is retarded, and eventually it is replaced. When the new chain is rolled in, both cam and IP are dialed back to the exact same place they were from the factory. Besides, a timing issue would affect the entire engine not just one cylinder.

The check for a woodruff key would be simple. With the new chain, put the crank at TDC and the marks on the cam should be dead on.

If the knock is something simple, driving it till it dies would be silly. Until the OP has determined definitively what the issue is, I suggest he drive it sparingly and gently if not at all. If it is something serious, a replacement engine may be warranted.

Diesel911 · #26 10-27-2015, 09:50 AM

Quote:

Originally Posted by cooljjay

No idea....Stranger things have been known to happen....

I can't figure out how the knocking could be the pcc....When the knocking is still there when the injector line is disconnected....Unless it is something echo'ing down the line, or something wrong deep in the engine...

Maybe a PO ran it out of oil, timing chain snapped, used head installed....who knows....Just would be interesting to know why the chain was replaced....something had to lead to that....Not like there is a highlighted sentence in the FSM that the timing chain expires at 100k....

Timing would effect all cylinders.

It is possible for the Fuel Injection Pump to have internal issues on #5.

It is also possible that someone could have fooled with #5 Element and screwd up the Fuel Adjustment or the timing on that particular element.

The only ways to know that would be to replace it with a known good used one or take the expensive way and have the fuel Injection Pump run on a test stand.

leathermang · #27 10-27-2015, 10:04 AM

Quote:

Originally Posted by mannys9130

.....The check for a woodruff key would be simple. With the new chain, put the crank at TDC and the marks on the cam should be dead on. ....

WRONG WRONG WRONG
The FSM specifically FORBIDS using the cam marks for determining the timing... it says it is only for a general ' quadrant ' check when PUTTING THE ENGINE TOGETHER at the factory.

funola · #28 10-27-2015, 10:36 AM

Quote:

Originally Posted by Tomas.brannholm

Hi,
I bought the car with the knock and it is only one owner before me. The service records is more then full and only on Mercedes workshops. The car is in super condition and AC, power windows etc is working. No new hoses for the oil cooler.

The problem is the knockind sound.

I have checked the oil pan and filter no babbitt or other metall.

I have checked the ball in the chambers and all ok, I will pull the chembers for inspection and cleaning. Part of the inspection will be inspection inside the cylinder with a boroscope. For reassembly I will put new collar nuts and selings.

Is it more checks I can do?

Thanks,

// Tomas.

If the pre chamber balls are intact, there is not much more that can go wrong with them other than erosion of the holes to bigger sizes. Pulling them just for inspection is a big job and not necessary IMO. Pre chambers are not easily clogged given the high temperature and pressure (over 1800 psi) inside.

leathermang · #29 10-27-2015, 11:17 AM

Quote:

Originally Posted by funola

If the pre chamber balls are intact, there is not much more that can go wrong with them other than erosion of the holes to bigger sizes. Pulling them just for inspection is a big job and not necessary IMO. Pre chambers are not easily clogged given the high temperature and pressure (over 1800 psi) inside.

' Big Job'.... not nearly as big as what is needed if the problem is the piston , pin , rod, crank...
it can be done from the top of the engine... AND when done also gives visual access to the combustion chamber .... which might show things like excessive carbon built up on a valve or the top of the piston .. or whatever...

Your assumption that only erosion to bigger sizes... is interesting first by the fact that you do not consider that a major problem...
and second because it is not true....
The pintel ball in the bottom of the precombustion chamber changed shapes over the years.... its shape was patented by MB....
It must work precisely with the small radially drilled holes to spread the atomized fuel in a proper pattern across the head of the piston... to the fuel is exposed to oxygen in an even manner...
" Not easily clogged " not sure what easily means to you... but the holes in the precombustion chamber are smack dab in the middle of a very harsh environment..... and checking them once every couple of hundred miles does not seem a rash suggestion by me given how important they are to fuel use efficiency.....
' 1800 ' psi... there are fish at the bottom of the ocean.. they survive because the pressure on their cells is equalized with the water pressure outside......being under pressure in of itself does not cause cleaning to happen..... and the temps in the combustion chamber will not melt carbon... so if for some reason carbon has obstructed one or more of those holes... only removal and careful cleaning will fix the obstruction.

mannys9130 · #30 10-27-2015, 11:22 AM

Quote:

Originally Posted by leathermang

WRONG WRONG WRONG
The FSM specifically FORBIDS using the cam marks for determining the timing... it says it is only for a general ' quadrant ' check when PUTTING THE ENGINE TOGETHER at the factory.

We aren't going for precision here, just a rough check to see if a key is installed. If there is no offset, the crank on 0 and the timing marks should line up. If there is a key, crank on 0 will show the timing mark too early and not quite on the mark. I understand that is not acceptable for precise measurements. We are just eye balling it and ruling out a key. Truth is it isn't even necessary because it is not the problem.

When you do diag for a bit, you realize most of the time initial checks are crude in nature and it's either a go or no-go situation. This is one of those times.