OM606 Delivery Valve Overfueling? - PeachParts Mercedes-Benz Forum

oilslick · #1 01-24-2016, 09:22 PM

Newly redone head and gasket has been installed on my 1995 E300. Started her up and she ran quietly and smoothly. I backed it out of the garage and went for a short test run (less than a mile). The engine reached operating temp but there was a pretty decent amount of unburned diesel smoke. Just before I pulled into my driveway the engine began to knock VERY LOUDLY. The engine began to miss but not terribly. I shut off the engine and got out to inspect. There was nothing visible that would explain the knock so I went ahead and fired it back up and the knock was not there but there was a faint miss. I pulled back into the garage and the knock came back to life. I shut it off to do a little more inspection.

The OM606 is not the most convenient engine to work on when it comes to getting to the injectors but I uncovered them and started the engine back up. It took a few seconds of running before the knock could be heard again. I loosened each injector line to isolate the knock and when I got to #6 I found the culprit. When I loosened the line there was an audible release of fuel pressure from that line (sounded like a spray can being sprayed for 2 seconds). The knock disappeared and with the line loose the engine ran relatively smooth.

While I had the head and intake off I replaced all the plastic fuel lines with brand new ones. I also replaced the delivery valve o-rings and crush washers. I've done this job before on several OM60X engines and have never had an issue but I'm wondering if I botched #6 on this one? Has anyone else experienced such high pressure on the fuel line before and if so, what did you find was the cause?

Thanks!
Kevin

ROLLGUY · #2 01-24-2016, 09:37 PM

I have not had a problem with the 606 (or any other similar pumps) that I have done the DV seals on. You could switch a couple injectors, and see if the knock follows the injector, just to rule that out.

oilslick · #3 01-24-2016, 10:36 PM

That is part of my plan for tomorrow. I need to find a deep enough 22mm socket for the injectors so I won't have to remove the valve cover to use my "other" method of removal.

Any explanation as to why fuel sprayed out of the line? All the other lines "spit" fuel out like normal but #6 literally sprayed a burst of fuel out then just bubbled.

ROLLGUY · #4 01-24-2016, 10:42 PM

Chances are it is not an injector, but it is easy enough to know for sure. You also may want to pull D V number 6 and look at it again. It may be obvious, or not, but it is best to start with the easy things and rule them out first.

m1tch · #5 01-25-2016, 02:59 AM

Have you checked the large O ring on the pre filter - might be letting a tiny bit of air past.

oilslick · #6 01-25-2016, 08:57 AM

Quote:

Originally Posted by m1tch

Have you checked the large O ring on the pre filter - might be letting a tiny bit of air past.

I appreciate the advice and I will check but I'm not seeing how that would cause the terrible knock. I'm not saying that it wouldn't but I'm just not seeing it. Thanks for chiming in. I really appreciate it.

funola · #7 01-25-2016, 09:21 AM

Quote:

Originally Posted by oilslick

I appreciate the advice and I will check but I'm not seeing how that would cause the terrible knock. I'm not saying that it wouldn't but I'm just not seeing it. Thanks for chiming in. I really appreciate it.

Air in fuel can cause knock and other symptoms. Air is compressible, fuel is not. When you have air in fuel, it can screw up the injection timing and when the cylinder fires, causing the knock.

oilslick · #8 01-25-2016, 10:58 AM

There's a definite miss and I suspect #6. The knock is no where near as pronounced this morning as it was last night (could be because the engine temp is still very low). Here's a little video to show the bubbling coming from line #6. When this line is opened there's no really noticeable change in the engine running. http://youtu.be/MMgL2SJ99nE

Maxbumpo · #9 01-25-2016, 11:02 AM

I vote for checking the #6 DV.

Some other fellow suspected his IP was messed up, so he removed all the hard lines and then filmed and posted on youtube the fuel squirting from the DV's as the engine was cranked over with the starter, and there was a very obvious difference between good and bad DVs. You may want to try that comparison "while you are there" to confirm a difference in that particular DV vs. the rest.

oilslick · #10 01-25-2016, 12:22 PM

Quote:

Originally Posted by Maxbumpo

I vote for checking the #6 DV.

I plan to pull the #6 DV when I get back to the house. I have some extra o-rings and crush washers so if it IS the DV then hopefully I'm good.

oilslick · #11 01-25-2016, 03:53 PM

I pulled #6 DV and there was nothing obviously wrong with it. Wouldn't ya know that I can't find the other new o-rings and crush washers that I have. They're here somewhere. I flipped the old crush washer over and reassembled the DV just for "giggles" and fired it back up. Still missing. Still smoking. Still bubbling fuel at the injector nut. The knock is not as noticeable and goes away when the injector nut is loosened. I am now in the process of removing the VC so I can swap injectors around (I do not own the correct socket for these injectors so I have to do what I have to do). This is the most inconvenient engine ever. I'm sure it's great engineering but such a booger to do simple things to.

EDIT: I'm pretty sure getting the same results after installing the same crush washer in the DV assembly speaks for itself. Have any of you seen where I put those new ones? Haha

What are the symptoms of a rod knock? Would a rod knock come and go? What fault in a cylinder would cause the fuel to bubble out like shown in the video?

Once I've got the injector out, what should I look for? I'm also going to see what kind of fuel delivery the IP seems to be giving via the DV's. I've got a feeling that I have a parts car available soon.

benedict · #12 01-25-2016, 05:00 PM

No it won't end up a parts car-just do things methodically.

You can swap your suspect number 6 injector with number 5 to see if the problem 'swaps' around but these bubbles are before the injector.

You have air getting in somewhere and the bubbles/air might just be ending up at the number 6 injector. So go over what you have touched.

You mentioned you replaced the plastic lines. Did you replace all of them and did you replace the line which requires the banjo bolt mod? Check your pre-filter has an o'ring as someone mentioned and it must be the correct part/o'ring as it's an unusual size from memory.

I know getting to things such as delivery valves and plastic lines require pulling the inlet manifold which can be a pain in the ?rse but once these engines are running nice they give years of trouble free motoring.

oilslick · #13 01-25-2016, 06:36 PM

Quote:

Originally Posted by benedict

No it won't end up a parts car-just do things methodically.

You can swap your suspect number 6 injector with number 5 to see if the problem 'swaps' around but these bubbles are before the injector.

You have air getting in somewhere and the bubbles/air might just be ending up at the number 6 injector. So go over what you have touched.

You mentioned you replaced the plastic lines. Did you replace all of them and did you replace the line which requires the banjo bolt mod? Check your pre-filter has an o'ring as someone mentioned and it must be the correct part/o'ring as it's an unusual size from memory.

I know getting to things such as delivery valves and plastic lines require pulling the inlet manifold which can be a pain in the ?rse but once these engines are running nice they give years of trouble free motoring.

I appreciate the encouragement. I replaced ALL the lines. I bought them from the MB dealership. The old line I replaced that requires the banjo bolt mod had been upgraded at some point and so was the new line I installed. As far as the pre-filter, it too came from the dealership. Shoot, even the cloth covered by-pass hoses on the injectors came from the dealership.

While I had the injector lines removed I had my lovely assistant, my wife, turn the engine over so I could see what the IP was doing. Every DV was shooting fuel up in the air at their given time. If any of them seemed suspect then it was #1 BUT it was the hardest to see without getting a fuel bath. I've bolted it back together and will now wait a while and bleed the air out and see what she does. I'm pretty confident it just a fuel issue. It comes and goes so surely it's just fuel.

funola · #14 01-25-2016, 06:45 PM

Quote:

Originally Posted by oilslick

There's a definite miss and I suspect #6. The knock is no where near as pronounced this morning as it was last night (could be because the engine temp is still very low). Here's a little video to show the bubbling coming from line #6. When this line is opened there's no really noticeable change in the engine running. http://youtu.be/MMgL2SJ99nE

After you cracked the injector nut in the video, it should shoot fuel out at each injection pulse. But that is not what I see. It appears bubbly fuel is coming out. Splice in a clear return to tank line, it should be bubble free with engine running and off overnight. If neither, then you have air intrusion.

oilslick · #15 01-25-2016, 10:38 PM

Quote:

Originally Posted by ROLLGUY

Chances are it is not an injector, but it is easy enough to know for sure.

I swapped #6 injector into #1 and #1 injector into #6 and I'm getting the same bubbling now on cylinder #1. What in the world is going on here? The symptom moved with the injector but what would cause an injector to do such?