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+--- Thread: Troubleshooting misfire (/showthread.php?tid=3577)
Troubleshooting misfire - Torkey - 04-25-2012
I have an OM617 with a misfiring cylinder that is driving me nuts. The symptom is a "oof" sound at the exhaust. The sound is louder when the engine is warm. Not as noticable when the engine is cold. Sounds like a stuck or burned valve.
I've adjusted the valves (2 times)
Here are the results of the compression test.
1-325
2-320
3-375
4-340
5-375
Cylinders 1 and 2 are a little low but nothing that would indicate a problematic valve.
Any ideas what the problem is and how to resolve it?
RE: Troubleshooting misfire - plurkje - 04-25-2012
If one injector is bad, it'll cause a misfire as well.
The compressiontest shows 2 out of 5 having a lower reducement of 10%. But that will probably only increase the engine shaking at idle. Could you show it on youtube?
RE: Troubleshooting misfire - MB TECH - 04-25-2012
While the engine is running at idle, crack the secondary lines at the nozzles one by one to narrow it down to which cylinder is causing the misfire. Once you figure that out make sure you are getting fuel to that cylinder from the injection pump. If all that checks out then I would start to suspect something internal.
RE: Troubleshooting misfire - Torkey - 04-25-2012
(04-25-2012, 02:34 PM)plurkje If one injector is bad, it'll cause a misfire as well.I popped tested the injectors when I had them out for the compression test and they were all good. Also have only about 4 months on these nozzles.
The compressiontest shows 2 out of 5 having a lower reducement of 10%. But that will probably only increase the engine shaking at idle. Could you show it on youtube?
Here's a video. Not sure how well the 'oofing' sound came through.
Video with the mysterious oof
(04-25-2012, 02:35 PM)MB TECH While the engine is running at idle, crack the secondary lines at the nozzles one by one to narrow it down to which cylinder is causing the misfire. Once you figure that out make sure you are getting fuel to that cylinder from the injection pump. If all that checks out then I would start to suspect something internal.Thanks for the idea!
I tried your test and I couldn't get the sound to go away. I'm pretty sure I cracked the lines enough because the idle went to crap and there was fuel spraying everywhere.
I think I will let the engine cool down and then run the starter (without glow plugs) and see if the sound is there when there is no combustion on any cylinder. I'll need to wait until my assistant gets home from work tho'.
I'm guessing it will be there. I've never heard of a diesel valve burning wondering now if maybe one of the valves is sticking.
RE: Troubleshooting misfire - larsalan - 04-25-2012
How about ye ole' italian tune-up? That outta free up some valves.
RE: Troubleshooting misfire - plurkje - 04-25-2012
the exhaust shows fumes in your way too short film, pop test or not the injectors aren't too good.
You are sure about the timing?
I think you should try with another set of injectors. These valves don't stick.
If the delivery valve spring(s) is broken shit like that can happen...
RE: Troubleshooting misfire - Torkey - 04-25-2012
I did adjust the timing a couple months of ago. Maybe I messed that up. Are you thinking the timing is too advanced or too retarded?
I'll check the delivery valve spring too. I never would have thought of that one.
RE: Troubleshooting misfire - willbhere4u - 04-26-2012
It could be a dead cylinder in the injection pump not pumping enough fuel in to one of the cylinders????
dose it only miss at idle? or dose it do it under load also?
With compression numbers like that I don't think you are having any valve problems!
First I would suspect the injection pump/fuel system plugged filter or bad lift pump
RE: Troubleshooting misfire - Torkey - 04-28-2012
I put on a straight exhaust a few months ago and I wonder if what I am hearing is just an artifact from the untuned exhaust.