OM606 engine wobble - Page 3 - PeachParts Mercedes-Benz Forum

Diseasel300 · #31 08-28-2018, 01:09 PM

The multiple tighten/loosen cycle is to guarantee that the copper crush washer seats fully. Remember that it's resisting >2000PSI during an injection event. Doing the tightening in a single step doesn't allow for compression of the metal and will result in a poor seal.

spock505 · #32 08-28-2018, 04:25 PM

I remember reading on one of the threads this procedure had been revised by MB to single torque, personally more comfortable with the former as makes more sense given delicate nature of set-up.

Waiting for my transmission mount to turn up, high hopes this at least might be a contributing factor, however comforted by the DV back-up now I have a better understanding of the workings.

I think you are either one of those people who accept and drive things or the other who like to pull things apart, putting yourself in the designers shoes thinking how can we make this work.

Back to the 962 v 910 parts issue, barrel and piston (elements?) is the parts swapped to increase fuel delivery, does anyone know if 962 and 910 are the same ?

I can measure both when out of pump but would be handy to know in advance.

spock505 · #33 09-03-2018, 08:29 AM

Replaced transmission mount today, much anticipation as old one looked fine but rubber soft and pliable, virtually no absorption qualities left.

...and nope, still there but the mount needed doing anyway, possible reason for burning out three center bearings ..

Diseasel300 · #34 09-03-2018, 09:52 AM

People like to claim that the engine and transmission mounts are there to prevent any engine vibrations from reaching the chassis. In part that's true, but they're not going to stop a rocking motion. The inertia from the heavy engine/transmission rocking back and forth WILL transmit to the chassis regardless of what kind of engine mount is used.

One question I've had that nobody seems to be able to answer is whether or not the M pump has any sort of a rack damper like the MW pumps did. If there's some sort of internal adjustment that could be made, that could be the answer. Like you I'm sort of out of explanations.....I have good compression, good injector spray pattern, no nailing, good power and economy, and smooth running except for that lopey idle that's present whether or not the EDS solenoid is energized.

spock505 · #35 09-03-2018, 11:00 AM

Tend to agree on your first comment, not sure about second as no knowledge of either.

Just back from 30 mile round trip, wish I had changed this a while back as trans shift much improved and very smooth.

This is not one of those components you can easily check , visually they look identical until compressed, good post on MB.org describes this well and so true.

Back to the wobble, it's 'just' still there, almost to the point of leaving alone which I may well do. The most likely is a DV not sealing imo, either one of the crush washers or the DV valve seal itself.

This type of fault will escape normal detection using pop tester/spray pattern, if the valve cannot hold pressure timing issue,delayed opening or even partial opening late causing a 'pink' effect.

I was thinking of making a small bow to wrap around wooden dowel, drilled out to hold top of DV - will check earlier thread for your comments Diesel.

spock505 · #36 09-03-2018, 11:11 AM

Thinking of it another way, the DV's are not balanced as you would expect from six injectors pop tested to within couple of bar - how do we know the DV's are performing equally well....this is one of my fist YouTube videos which surfaced on an unrelated Google search.

The story behind this was trying to establish when number one pot was on injection stroke, marked the aux belt with paint 15 degrees ATDC..

..hey, don't laff it worked ..

https://www.youtube.com/watch?v=SQ5KIgWatJk

One way to check your DV's..

Diseasel300 · #37 09-03-2018, 11:34 AM

Not sure how that would test the DV's. The amount of leakage required to cause nailing is minuscule in comparison to the amount of fluid pumped by the pumping element, even at idle. If the DV's are worn so badly as to cause a dead-miss, you have more serious problems!

spock505 · #38 09-03-2018, 11:56 AM

From what I understand about this design not all the pumped fuel makes into high pressure side, isn't there a bypass back into the galley via piston element?

I would be surprised if nailing is the only symptom of poor DV seal/s, the amount of fuel emitted at nozzle end is small, very small getting that balanced with the rest is quite a delicate operation - example, what about if over-torqued, the barrel element may not rotate smoothly, instead juddering.

Up until now there's been a general paranoia about touching anything below crush washer, not much written on subject in terms of solutions, btw, did you replace your crush washers after re-torquing each time?

On a couple of mine I didn't in fact no: 6 removed the other day has been torqued up 3 possibly 4 times using same washer, good place for me to start.

Diseasel300 · #39 09-03-2018, 12:14 PM

The overflow port is part of the pumping element, not the delivery valve. The delivery valve is literally JUST a check valve. That's it! When the pressure is high enough to pop the injector, the DV unseats and the fuel flows in the hard line until the pumping event is complete (pumping element reaches the top of its stroke). At that point, pressure drops in the hard line, the DV re-seats (and creates a slight pressure drop in the line to ensure positive cutoff of the injector) and creates a liquid-tight seal to prevent the hard line from bleeding down.

All of the rotating and spilling is done in the barrel of the pumping element, which is before (below) the DV. The DV is literally the same concept as a check valve in a plumbing system. It allows fluid through one direction, but not the other. Instead of dealing with 30-100PSI of water mains, it's dealing with 2000+PSI in the injection system. Thinking of the DV as anything other than a high pressure check valve is overthinking the situation.

I've dealt with the crush washers too. I've reused some before, and I did get nailing - very loudly. Replacing them every time the holders are removed is an important step. They're cheap, just do it. Always replace the O-ring at the same time. I've also found it necessary to wipe the threads and O-ring with diesel fuel before insertion to get accurate torque - a step that's often left out of writeups.

spock505 · #40 09-03-2018, 02:02 PM

..ta.. Diesel, good post - my mild disappointment has been somewhat overshadowed by the transmission improvement, that said getting the ''wobble' sorted however minor would be the icing ..

Forgot to take serial number off pump while tray removed, going to order full kit as per link above PLUS the contentious - springs - direct from MB.

With regard to copper washers, did you notice any change after they had been in use? - i ask as those on 962 were considerably thinner (worn?) then the newer 910 additions.

As mentioned before, the ordering process was a little hit and miss which always causes concern, especially after ordering those auto box valves.

reading the turbo forums, 962 uses 6mm elements often replaced by 7.5 or even 8mm - any idea what size 910 is for swap- ability ?

Diseasel300 · #41 09-03-2018, 02:16 PM

I've gotten to the point that I ignore the lopey idle on mine. Nobody else seems to notice it and it only really gets annoying when sitting at long traffic lights. Sometimes it goes away entirely and the engine idles smooth as silk. Normally it's very soft, unobjectionable. Occasionally it's enough to be annoying and make the car jiggle, sometimes accompanied by minor nailing. One of these days I'll finally work out what it is and solve it, probably completely by accident.

The crush washers should be the same regardless of turbo or non-turbo. I've noticed no difference after use other than the "tractory" qualities quietening down after a few hundred miles of driving. I don't have tens of thousands of miles on mine yet, so I don't know long-term any sort of wear first hand.

Not sure on the pumping elements on the turbo vs n/a pumps either. I've read that all 601/2/3's used 5.5mm elements regardless of turbo or n/a. I know the 210's use 6mm elements, not sure about the 124's, but I'd expect them to be 6mm maybe? You could always measure the bore with a caliper to find out. Using a different size pumping element requires recalibrating the injection pump.

spock505 · #42 09-03-2018, 02:51 PM

Here's my current thinking, bear in mind the video posted above with paint marker on aux belt.

I have six spare injector lines, six almost new injectors -

Proposed solution:

Mock up a similar rig to above video using spare injector line, encase injector inside 5 litre clear plastic bottle to observe spray pattern ...wait for it....

..when running, i.e pull one line at a time leaving everything else in place (5 other injectors) - this is not dissimilar to pop testing the injectors themselves, only difference is using a live rig -

It's clear during pop testing any deficiency so hopefully same lines here, if it throws up one odd pot then investigate in normal fashion..

Diseasel300 · #43 09-03-2018, 08:04 PM

If the injector has a good spray pattern on the bench, it's gonna have a good spray pattern on the engine running, the delivery valves and pumping elements have no effect on spray pattern. The pattern is not what's important here anyway, it's the injection QUANTITY as well as the exact timing. You cannot accurately measure either one in your driveway, the IP would have to be pulled and put on a calibrated test rig to determine anything useful. By the time you did that, send the damn thing off for rebuild, it's only another hundred bucks or so at that point compared to the time and expense put into testing the IP.

spock505 · #44 09-04-2018, 01:46 PM

You misunderstand, it's not about measuring but performing the same visual tasks as you would pop testing - lets see if all six match each other, if one is a bit out of sorts that could be suspect.

Most of pop testing is visual, checking chatter, spray pattern and so on - i know the injectors are good so any variance is pump side.

Thinking about it, this is a lot quicker than pulling all six holders, no priming either - just plug and play.

I have a small pipe bender for the job.

Diseasel300 · #45 09-04-2018, 01:57 PM

Quote:

Originally Posted by spock505

You misunderstand, it's not about measuring but performing the same visual tasks as you would pop testing - lets see if all six match each other, if one is a bit out of sorts that could be suspect.

Most of pop testing is visual, checking chatter, spray pattern and so on - i know the injectors are good so any variance is pump side.

My previous point still remains valid. If the injectors test good on the bench and have good pop and spray patterns, they'll do the same on the engine. If the IP develops enough pressure to pop them, it's going to be the same pattern they did on the bench. There is nothing in the IP that will affect pop pressure or pattern.

If the IP is ruined enough internally to be causing a dead-skip at idle, it should be easily identified by simply cracking the injector lines one at a time and finding the one that makes no difference.

If the IP is marginal on one cylinder, cracking the lines one at a time and finding the cylinder that makes the least amount of difference will identify the cylinder that needs further investigation pretty quickly.