617 weird behavior diagnoses - PeachParts Mercedes-Benz Forum

OM617YOTA · #1 10-28-2014, 04:30 PM

Please help! Going to give this one last shot before throwing myself on the mercy of an MBZ shop. Here are my symptoms:

1. Miss and pinging at idle when cold. Turn on glow plugs, miss goes away.
2. Pinging like a gasser at part throttle at all engine temps, much worse when cold. Only pings at certain throttle positions when warm, like when cruising down the road, then it sounds like I have ball bearings in my cylinders. Give it more throttle or let off the throttle entirely and it goes away.
3. Loud clacking or metallic noise when off throttle and coasting down in gear.
4. All of this is getting worse.

I have:

1. Greazzer rebuilt the injectors. Twice. I'm confident they're fine.
2. I set the timing using the drip method. No difference. I moved the timing in two degree increments backwards and forwards until the engine wouldn't run in either direction. Pinging and miss still present at all timing settings.
3. Killing individual injectors does not change any of this.
4. Ran the engine off a bottle of fuel in the engine bay, observing fuel returned to bottle for air bubbles and such. There were none.
5. Ran two cans of diesel purge through it. No junk came out in the bottle, no change in running when switched back to diesel.
6. Valves have been recently adjusted, compression was decent and even across all 5 cylinders.
7. Glow plugs all test fine. They were viewed in the engine with the injectors out, tips glowing brightly.
8. Been through a mess of filters.

What am I missing? Did I fubar my injection pump during drip timing?

Thank you all. Really scratching my head over this one. There's a local-ish guy who's been working on MBZ diesels for 40 years, next step is dropping it off with him.

leathermang · #2 10-28-2014, 04:57 PM

Pull your pre combustion chambers out and make sure the holes are clean...and the pintle ball is in place....

mach4 · #3 10-28-2014, 07:34 PM

Quote:

Originally Posted by leathermang

Pull your pre combustion chambers out and make sure the holes are clean...and the pintle ball is in place....

That was the one thing I was thinking as well. The only other thing I can think of is something with the IP, maybe the delivery valves.

leathermang · #4 10-28-2014, 07:41 PM

He has covered so many other things... it was the only thing central to the working of the engine I could think of....

OM617YOTA · #5 10-28-2014, 10:57 PM

Thank you, guys.

The pintle ball was in good shape when i had the injectors out last. Guess I'll start collecting tools to remove the prechambers.

Another couple possible symptoms came to mind. It's had gray smoke just about the entire time I've owned it, hot or cold. It's gone away for a while after having the injectors rebuilt and after the diesel purge, but always came back. It also blows a good bit of blue smoke on first take off after sitting for a while. Sit overnight, crank up, idle out of the driveway and down the street to the main road, pull out on the main road and give it some throttle, and get a big cloud of blue smoke. Goes away by the time I get to third gear. Same thing at lunch time at work, and particularly noticeable after a long period of idling.

leathermang · #6 10-28-2014, 11:57 PM

Ok... that description adds the possibility you need new valve stem seals.....

Stretch · #7 10-29-2014, 05:01 AM

Is the misfire / stumble happening at speeds other than idle?

The clouds of blue smoke at start up could be more than just the seals I'm afraid to say.

leathermang · #8 10-29-2014, 07:39 AM

Quote:

Originally Posted by Stretch

......The clouds of blue smoke at start up could be more than just the seals I'm afraid to say.

I totally agree with that possibility..... what test/s do you suggest to determine that ?

Stretch · #9 10-29-2014, 08:49 AM

Quote:

Originally Posted by leathermang

I totally agree with that possibility..... what test/s do you suggest to determine that ?

Unfortunately I can only think of the wiggle test => gripping hold of the valve and wiggling it in the guide.

This is best done with the head off (well better still with the head off you measure the guides with a go-no-go gauge) but it is possible you might get an idea by positioning the piston near to TDC and then wiggling the valve from the other side. Rocker arms and valve springs need to be removed along with the valve stem seals. Make sure the piston is high enough in the cylinder to stop the valve from disappearing if you drop it! Any noticeable feeling of a gap probably means that if you were to use the correct go-no-go tool you'd (again probably!) find that the guide was worn.

leathermang · #10 10-29-2014, 10:01 AM

Hopefully the ' not removing the head' tests will find a solution..
BUT.... if one want to do the wiggle test without taking the head off... then when the precombustion chambers were out would be the ideal time... being able to see that the piston is in the proper place...
Note... it would be safer to clamp in some way the crank to prevent accidental movement of the pistons when you do not want it....

Stretch · #11 10-29-2014, 02:20 PM

You can also determine approximate TDC of a piston in other ways such as looking at the cam shaft lobes - removing the glow plugs (which is helps turning the crank anyway) and feeling for air being forced out of the cylinder on the compression stroke - knowing that after cylinder 1 on an OM617 the next cylinder to reach TDC is #5 and then #2 then #3 then #4 (very different from the firing order!) and that these happen at a spacing of 72 degrees - alternatively you could rotate the crank shaft a whole lot more (twice as far) and find the TDC after each compression stroke by following the firing order often on the valve cover which is 1,2,4,5,3 here you need to turn the crank by 144 degrees between "each TDC"...

leathermang · #12 10-29-2014, 02:59 PM

But I was suggesting he pull the precombustion chambers anyway..... foolproof cylinders up indicator....

OM617YOTA · #13 10-29-2014, 03:53 PM

Thank you folks, I really appreciate the help. I guess yanking the prechambers is the next step. Time for a Peach Parts order for seal rings and heat shields.

Could my turbo seals be shot and leaking oil into the intake? Oil would act as fuel and could cause my pinging, could have carboned up or damaged the prechambers, could be causing the clouds of blue smoke at startup. Might be worth yanking the turbo and checking for oil in the intake. Scary thought, what are the odds of a runaway engine?

OM617YOTA · #14 10-30-2014, 08:48 AM

Something else came to mind. When idling, if I turn on my glow plugs, the miss and the pinging goes away. I'll check on how it effects pinging while driving when I get off work.

To my inexperienced mind, that points to my IP and timing being fine, and I really need to yank those prechambers.

barry12345 · #15 10-30-2014, 11:01 AM

When the problem started? Especially if just after you did something would be important to post.

I dislike wild guesses and this is one. It almost sounds like your centrifical mechanical injection pump advance system is sticking in an advanced position. Not all the time though. I also wonder if the blue smoke is related or could be. My first thought is I think not.

Never heard of one of these cars doing it though. It would take some form of electrical firing timing device to prove it. I am not suggesting you pursue this particularily at this time.

Just to keep it in mind. What disturbed me was the idle getting better with glow plugs turned on although you have good compression. Plus loosening one injector line at a time makes no differance basically so it is not related to one cylinder.

This eliminates you messing anything up with the injection pump when retiming the injection pump as well. To me symptomatically it almost sounds like the injection pump is way advanced when it should not be. I just feel that the clues are there but I cannot grasp them properly yet if ever.

Once again the idle quieting down with glow plugs applied may not quite fit in with my thoughts at the same time. That is a very important clue to a guy like myself.

It for example would not delay ignition in my mind but that sounds like what may be happening. The excess smoke is kind of another wild card that may not fit well. Also is your egr valve staying closed when it should be?

I will be watching your thread as your problem is very interesting. This also will help make me think about the problem in a little more depth.

Well at least having a Mercedes mechanic with forty years diesel experience available is a real upside if it comes to it. I would not like to drop a problem like this on some of todays mechanics. Also if he is friendly have you talked to him at all about what he thinks? My guess is he may have seen this issue before.

One test I might do to verify the balancer mark is accurate. Remove the number one injector. This with the engine some degrees before top dead centre. Rotate the engine slowly. The oil should be visable coming up to level. When it stops rising this verifies the piston is at tdc. A straw can make this a very accurate level check. I left out that you have to add oil to the cylinder.