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#1
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missfire on Cyl 2. At a loss, please help!
I have done A LOT of troubleshooting so bare with me... About a month ago picked up a 84 300d turbodiesel with 173k miles. started and ran perfectly but previous maintenance was unknown so I adjusted the valves (all exhaust too tight, most intake ok or slightly loose) fixed all vacuum leaks and replaced all fuel hoses along with the primer pump. Test start the car ran fine but the next day after a long drive it began idling badly and smoking greyish smoke at idle (especially while cold). i figured an injector was bad so decided to replace all of them with new bosch injectors, but this did not solve the problem. I narrowed it down to the number two cylinder by cracking injector lines one by one. it ran worse with each except cyl 2 which cracking the line did nothing. I tried swapping injectors around just in case and issue always stays with #2 cylinder. At this point i figure I must have messed something up with the valve job so I redo it entirely taking extra care at which were exhaust/intake and getting them PERFECT (slight drag with cam lobes in 1 o'clock position/90 degrees to platform lobe makes contact with). all were fine. I bought a compression tester and cylinders 1,3,4,and 5 were right around 400-425. cylinder #2 was 290. I poured a few ounces of oil into the cylinder let it soak for a bit and repeated the test with compression only going up slightly to 300-305psi. so I checked and redid cylinder 2's valves AGAIN with everything looking fine and checking out. Additionally I have inspected the pre-chamber and it does not look particularly dirty with the ball and glowplug in there correct places. No oil in coolant no overheating issues smoke does not look or smell like coolant. I am about to pull the head and inspect the valves or just give up. Any ideas of what could be causing this? Prior to the compression test I was dead set it was a fueling issue but now I'm thinking there is not enough compression to ignite the fuel at idle on cyl 2.
TLDR bullet version: -om617 turbo motor with essentially no blowby doing oil cap test -has great power and runs PERFECTLY off of idle. -cylinder 2 is not igniting fuel properly at idle causing misfire and puff of smoke -brand new injectors and no air leaks in fuel -Cyl 2 has 290PSI of compression (100PSI less than neighboring cylinders) -car ran fine before valve adjustment after adjusting its almost like the valve no longer seats correctly. -I have adjusted the valves 3 or 4 times at this point, Cyl 2 is Intake then exhaust and setting gap at .10mm and .35mm respectively. Thank you for reading all this, any help or suggestions are greatly appreciated. Hoping someone out there has an idea i do not! |
#2
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What does "TLDR" mean?
How much experience do you have adjusting valves? Where is the car located?
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Respectfully, /s/ M. Dillon '87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted '95 124.131 (E300) "Sapphire", 380k miles '73 Balboa 20 "Sanctification" Charleston SC |
#3
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Your next test should be a leak-down test on #2 so you can determine if the loss of compression is through the valves or through the rings (or a hole in the piston).
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Respectfully, /s/ M. Dillon '87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted '95 124.131 (E300) "Sapphire", 380k miles '73 Balboa 20 "Sanctification" Charleston SC |
#4
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I think if you do a leakdown test you're going to find a compression leak through that cylinder in the valves. If you did a teaspoon of oil in the cylinder and didn't see a drastic raise in compression, you're bottom end is fine. It's most likely a valve. I'd do that test to 100% verify, but I'm about 90% sure it's a problem with your valve. No reason to replace or teardown anything yet.
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Only diesels in this driveway. 2005 E320 CDI 243k Black/Black 2008 Chevy 3500HD Duramax 340k 2004 Chevy 2500HD Duramax 220k |
#5
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Quote:
Good job troublshooting. When you swapped the Injectors and there was no changed as you said that indicated it was not the Injector. You took the compression test and found a low cylinder. You put Oil into the cylinder (which normally is not done on Diesel Engines because there is a chance that Oil pooled on the top of the piston could ignite a bit and ruin your compression tester gauge). So I think you have found evidence that it is not the rings/piston/cylinder. Becaue normally oil in the cylinder would raise the compression if it was an issue with the rings/pistons/cylinder. All that I can think of that is left is an issue with the not seating well or a head gasket leak. If you have an Air Compressor (better if it has a water filter to keep water out of the compressed air) you could mod your compression tester adapter so you can apply compressed air into the Cylinder with the valves closed and it is supposed to be at TDC or close to that. then you listen for leaks in the intake or exhaust maifold to see if it is a valve seating issue. I am not sure how easy it is to here if air is leaking into the crankcase for a rings/piston/cylinder issue. If the headgasket is leaking out side you might here the air hissing out. If there is a head gasket leak into the coolant after you drive the Car sufficently get it good and hot; shut it off and park it for 2 hours or more. Afterwhich squeeze the upprer radiator hose. If that hose feels hard and inflated you have a head gasket leak into the coolant. You also might be able to see bubbles in the coolant recovery tank or it could have that burnt combustion smell. If everything is OK in the above tests all that is left is the Fuel Injecion Pump. Perhaps some issue inside the #2 element (if you have an MW Fuel Injection Pump don't loosen the 2 13mm Nuts on each side of the Element).
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84 300D, 82 Volvo 244Gl Diesel |
#6
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TLDR = too long, didn't read
a brief synopsis either preceeding or following a wall of text tldrs are a boon for folks with short attention-spans, like me
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1991 300D |
#7
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Quote:
Tonight I played with the rack damper bolt and looks like i need a new one of those. tightened all the way in did not really do anything for idle and engine still starts right up. I raised the idle to about 800rpm to try and mask the misfire and it seems to be mostly firing on all cylinders now but at this point is smoking grayish-black smoke just about all the time. low compression can cause smoke too though correct? Thanks and sorry for the giant walls of text, just like to put as much info out as i can. |
#8
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__________________
Respectfully, /s/ M. Dillon '87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted '95 124.131 (E300) "Sapphire", 380k miles '73 Balboa 20 "Sanctification" Charleston SC |
#9
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How many times did this car start up and run perfectly before you adjusted the valves?
How much experience do you have adjusting valves? I keep coming back to the sequence of events where all the trouble started after you adjusted the valves. Injection pump and the two 13mm nuts on the delivery valve plunger assembly: These affect the quantity of the fuel that the injection pump sends to that injector. If these have been moved, the pump is out of calibration, unless they were moved by a Bosch-trained technician on a test bench. If you can discern the original position, try moving it back, as you've got nothing to lose at this point. You could also perform a rough calibration using a set of graduated cylinders (lab equipment - think test tubes marked up for liquid volume measurement) that catch all the fuel from each delivery valve / injection line as you crank the engine over. Compare the volume of diesel from each position, adjust #2 to match the others.
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Respectfully, /s/ M. Dillon '87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted '95 124.131 (E300) "Sapphire", 380k miles '73 Balboa 20 "Sanctification" Charleston SC |
#10
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Quote:
I started and drove the car maybe 3 times before doing all the maintenance, and I know that I test started it after completing the valve job and it started and idled fine. I believe it was the next drive (over an hour on the highway both ways) that I arrived home and it was running on 4 cylinders at idle. I'm beginning to think it was coincidental that the valve job preceded the issue... I think when I have a chance I will try my luck with the injection pump's 13mm nuts i'm not supposed to touch. If nothing else maybe I can see if it greatly effects it and decide to purchase a used pump or send mine out for re-calibration. If it doesn't do anything probably bring it in to a shop to perform a leak down test and maybe give some insight from experience I don't have with diesels. If i'm going to go all in and pull the head I at least want 100% confirmation that is the issue... Also, any idea on cost of getting a pump re-calibrated? Thanks. |
#11
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Even if the compression is lower on the one cylinder. It is still high enough for combustion to occur. Technically the cylinder is just a little weaker. Totally dead should not be expected.
Since apparently it was running well something odd like the number two elements piston is stuck at the top of the bore might be possible even. Seldom does pump element failure occur this quick. Not impossible of course. A chunk of dirt in the delivery valve might also have disabled it. Since there might be a possibility that a valve is not closing at running rpms on that cylinder as well. But pretty much closes at cranking rpms. I might put that number two injector out in the open on a line and watch if it is spraying. I would want to define what I was chasing before moving on. Although the lower compression on that cylinder in combination with it not working points away from the injection pump. Could just be circumstantial of course but I would not count on it. My posts are all too often long and painful. I would still want to know if it is the cylinder itself malfunctioning or no fuel from the injector before doing anything else first. The lower compression for example could result from a valve that is closing slower for some reason. So at running rpms it could reduce the compression substantially. Anyways the adjustment for the element on the pump is not going to jump way off all by itself so leave it alone until you have a better ideal of what is actually going on. Just my opinion though. You may need an injector line from a junk car to test for the number two injector spraying. Or pull the glow plug to see if it is dry or wet. If the cylinder is getting fuel and not firing it should be wet. Matter of judgement in many cases. Comparison to one from a working cylinder if needed. You could increase the misery by tampering with the element adjustment at this point. Again elements adjustments do not all of a sudden jump out of whatever calibration they had. . Last edited by barry12345; 09-15-2017 at 09:02 AM. |
#12
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I'd stop looking at the injection pump and figure out why your compression is so crappy on Cylinder 2. A 135PSI difference in compression between the adjacent cylinders is going to cause a NOTICEABLE "skip". The cylinder will still be partially combusting and contributing a bit of power, but so much less than the other cylinders that it will seem like it is missing out.
The maximum acceptable compression difference between 2 adjacent cylinders is somewhere around 10%. You're at 32%. That's a BIG loss of power, even if the injection pump is squirting fuel in the cylinder. As suggested above, get a leakdown tester or blow compressed air in the cylinder and figure out where it's going. If you have a valve that isn't seating you'll hear the air coming out of one of the manifolds. If you have bigger problems you'll hear the air in the crankcase. |
#13
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After the leak-down test, another way to test the injection pump would be to remove all the hard injection lines, put some rags around the top of the IP to catch the fuel from the next step, and have a helper crank over the engine while you watch the fuel output from the delivery valves. Each should "spit" a little or a lot of fuel up, depending on the accelerator position (idle or off idle up to floored). Should look like a little display fountain throwing fuel up in the air and inch or two. Any obvious difference between #2 and the others will let you know your next step.
__________________
Respectfully, /s/ M. Dillon '87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted '95 124.131 (E300) "Sapphire", 380k miles '73 Balboa 20 "Sanctification" Charleston SC |
#14
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Injection pump fiddling is for after the source of compression loss is identified and corrected. Even if the pump were new and calibrated, #2 would be a source of problems because of the extreme low compression compared to the other cylinders. The grey smoke is a clue that fuel is being injected but not burned (low compression).
Put the horse in front of the cart. Find and fix the compression issues then determine if you have problems with the injection pump. It was running before, since you didn't take anything off of it or fiddle with the internal components it should still be fine. |
#15
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figured i would give a quick update since i found this issue in case someone in the future is having similar issues. I did some more troubleshooting and decided it was time to pull the head. Ended up being a broken valve guide. I dont understand how a valve guide can snap like this but googled it and saw it has happened to other om617's... Maybe someone else can shed some light on what could have happened? Good news is valve seat itself looks in good condition, no nicks or scoring. same with pistons and cylinder walls. this was a $1200 car so not going to go crazy throwing money at it, I'm just going to drive out the old valve guide and install a new one along with a new valve, valve stem seals and do some lapping compound to mate the new valve to the seat. I know I could get a full head rebuild but just looking to get it back on the road at this point.
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