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Author Topic: Head off, injector out, questions.  (Read 12108 times)

contaucreek

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Head off, injector out, questions.
« on: May 17, 2008, 10:25:47 PM »
 The injector came out easily by just putting a big adjustable wrench on it and cracking it free by rotating it.The spray seems to come out at an angle and is a nice tight mist pattern. Inside of combustion chamber is pitted as is the top of the piston, is this normal?? Carbon deposit very minimal. Exhaust valve seems to be harder to rotate by screwdriver than the intake valve but both seem to seat OK.Cylinder nice but seems to have a small area on the injector side  up near the top that is slightly larger than the bore and I cant tell if this is normal. The reason for the head off is to diagnose a smoking condition that seems to occur when the governor is relaxing the fuel and the engine is deccelerating, whispy streaks of white smoke.When I open the COV the engine then smokes like theres a hole in the piston !!The thing slobbers badly but the combustion chamber and valves are bone dry. What should I be looking at ? Possible COV seat problem, spill timing, maybe go the extra and look at the rings and piston ? Based on the videos of other Cs' mine is a smokey unit !! PS- the governor seems to have a slight sticky spot. When you throw it open to start should it pull the rack totally out because mine requires a slight assist to pull it out the remaining 60 or 80 thou. Anyway hope to hear some good suggestions and to my fellow Canadians have a safe V.D. weekend LOL.
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Stan

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Re: Head off, injector out, questions.
« Reply #1 on: May 18, 2008, 12:26:31 AM »
Can't help withe everything but yes Penelope has pitting on the piston top.  COV valve, do you open it FULLY?   There's no such thing as partially opening a cov valve.  Kind of like there's no such thing as being almost dead, you either are, or you aren't.

Good instructions on how to clean a cov assembly in the Lister manual, you might have to have it reassembled however, to break the inner part free using compression.

Stan

contaucreek

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Re: Head off, injector out, questions.
« Reply #2 on: May 18, 2008, 05:02:43 PM »
Yes Stan, open fully.
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Stan

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Re: Head off, injector out, questions.
« Reply #3 on: May 18, 2008, 10:27:46 PM »
OK, then it needs cleaning.  Do you have a manual?
Stan

contaucreek

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Re: Head off, injector out, questions.
« Reply #4 on: May 18, 2008, 11:28:00 PM »
Remove and clean the COV I assume then. I have a manual. I downloaded it and put the pages in plastic sleeves and stuck them in a binder, handy for the shop and easy to wipe clean. Why would a dirty COV cause it to smoke??
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Stan

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Re: Head off, injector out, questions.
« Reply #5 on: May 19, 2008, 03:16:47 AM »
It'll cause it to suck air in around the cov valve stem and screw up the fuel air mixture.  N'est pas?
Stan

oliver90owner

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Re: Head off, injector out, questions.
« Reply #6 on: May 19, 2008, 07:02:57 AM »
Stan, I hope you are joking. :)

Stan

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Re: Head off, injector out, questions.
« Reply #7 on: May 19, 2008, 03:37:44 PM »
Nope!  Not joking about the air being sucked into the head around the cov valve stem, if that's what you mean. 

If you look at the cut away diagram of the head in the manual, you'll see a "knob" at the end of the cov valve stem.  When it's screwed in all the way, it seals the small spherical chamber off (decreasing the volume of the head castings) and when it's screwed out all the way it seals the "outside" of the small spherical chamber (increasing the volume of the head castings).  When it's only screwed in partway, or not sealed because it's got crud on the "knob" (or generally in the spherical chamber)  it allows air to be sucked in to the head around the cov valve stem.  The cov valve stem, to my understanding does not have any sealing mechanism on it.

If anyone disagrees with what I'm saying please chime it!  I'm not infallible (don't tell my wife).
Stan

contaucreek

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Re: Head off, injector out, questions.
« Reply #8 on: May 19, 2008, 08:07:59 PM »
Would be easy to diagnose with soap and water around COV screw and look for bubbles ?? (no not from the trailer park boys). Didnt even consider this was a possibility. Upon closer inspection the undercutting of the bore seems to be just  where there was not enough material to fully bore the diameter.I dont think it goes down enough to hit a ring. I may extract cylinder up and off and service to rings, take measurements etc.Thanks Stan.
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adhall

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Re: Head off, injector out, questions.
« Reply #9 on: May 20, 2008, 04:35:56 AM »
Stan,

I think you are confusing gasoline and diesel engines.

First of all, the diesel has no throttle so there is relatively little vacuum developed during the intake stroke. And since there is no throttle, the diesel engine draws in the same amount of air with each intake stroke regardless of the power output (assuming constant speed) . This means that when running at less then full power, the diesel combustion chamber has excess air (oxygen) in it. So even if you were sucking extra air in during the intake stroke, how could this possibly do any harm? In other words, for a diesel, the concept of "fuel mixture" doesn't apply.

It's clear to me that what is really happening when the COV is in mid-position is that you are losing compressing by having air from inside the cylinder leaking out around the valve stem. It is this loss of compression that that causes the smoking.

Best regards,
Andy Hall
JKSon 6/1, 5 kW ST Head, 1992 Dodge RAM Cummins 5.9L Turbodiesel, 2001 VW TDI 1.9L Turbodiesel, 2006 Jeep CRD Turbodiesel, Yanmar FX22D Diesel Tractor

Quinnf

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Re: Head off, injector out, questions.
« Reply #10 on: May 20, 2008, 04:54:32 AM »
TCylinder nice but seems to have a small area on the injector side  up near the top that is slightly larger than the bore and I cant tell if this is normal.

You're saying there is an irregularity in the cylinder wall?  Like a gouge?  Any groove or gouge or visible mark in a cylinder wall could allow lube oil to be forced up past the rings on the intake stroke which would then burn on the next power stroke.

COV valves are sometimes problematic.  A few cases of the COV valve slowly loosening while running have been discussed on this forum.  And Stan's right about there being two positions.  Open and Closed.  While making the transition from open to closed after startup the videos I've seen indicate there is significant leakage around the shaft until the valve is fully closed.  Apparently the noise the engine makes while making the transition is enough to wake you up if you haven't had your morning caffeinated beverage of choice. 

I presume you're talking about a real English type Lister, and not a 'roid, right?  Some of the Indian manufacturers have sold 'roids with COV valves which don't run well because the combustion chamber volume was optimized for use with the plug.  Some folks that have had those have reported smoking and the engine failing to run well with the valve in the open (RUN) position.

Quinn

Ashwamegh 6/1, PowerSolutions 6/1 "Kit" engine, and a Changfa R175a that looks like a Yanmar I once knew

Stan

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Re: Head off, injector out, questions.
« Reply #11 on: May 20, 2008, 05:24:46 AM »
Andy, yah you're right, I wasn't sure what "smoking" meant.  Was there white smoke coming out of the exhaust, or was it coming out of the cov valve stem area.  Quinn's right about the noise when the cov is mid position.  Anyway, it's a pretty simple fix to remove the cov valve, give it a good cleaning and try it  ::)

You don't have to disassemble anything, just the cov!  Seems like KISS is still the best principle.  ;D
Stan

craig c

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Re: Head off, injector out, questions.
« Reply #12 on: May 20, 2008, 06:39:32 AM »
Hi White smoke  is oil been burnt in exhaust , coming down ex guide I would say , black smoke is unburnt fuel , blue  smoke is oil burnt in combustion , there is only 3 types of smoke in a diesel , craigc .

Stan

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Re: Head off, injector out, questions.
« Reply #13 on: May 20, 2008, 03:14:48 PM »
Would that be influenced by opening the COV valve?
Stan

craig c

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Re: Head off, injector out, questions.
« Reply #14 on: May 20, 2008, 07:59:51 PM »
Hi stan , It may do , is the ex valve oily and in port , the pitting will be water in cylinder head gasket leaking , craigc