This is good information to know.. Thank you. I'll do that with my next test.
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The same glow plug constantly roasting mystery..
- Thread starter Humpty
- Start date
I had my scope in the injector hole each injector/glow plug replacement looking around for hunks of glow plug.. terrified they’d fall down into the cylinder. Nothing jumped out at me but i’d planned on giving them a good look again tomorrow.
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I'll come back to this again. The twitching of my right testicle just won't stop until the question is answered.
Especially as the answer is quite simple and straightforward.
Replace the plugs on the spark plugs and see if the fault moves with them.
Especially as the answer is quite simple and straightforward.
Replace the plugs on the spark plugs and see if the fault moves with them.
You mean move the injector on the cylinder in question to see if the problem follows? I essentially did that twice. Once with the cheap injectors and again with the Delphi injectors. The injector clearly isn’t the problem. Neither is the start box or the glow plugs since it’ll swell the glow plug having never been connected to power.
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No, not the injector... the glow plug cable!
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When you scoped the pre-cup can you see that it is intact, can you see the little "window" going into the cylinder and it looks like the others?
cucvmule
collector of stuff
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Have you done a wet test on the trouble cylinder. The same with the adjacent cylinder with the low 280 reading?
Wet test and dry can narrow down the symptoms to specific causes.
What I see as troubling as the glow plug is "melting" many glow plugs and the piston is not having any damage as well, melting at the ring land or cracking from too much fuel. I have always replaced any Wellmans with A/C Delco when I see them on trucks. The Delco glow plugs in my experience are the best you can use. I have Delco in my 82 civi that have been in there for over 25 years and still work fine. When I got the CUCV 1008 I took out the new wellmans and replaced with Delco's right away.
The melted pieces have to go somewhere, I have seen chewed up pistons, valves scared from glow plug pieces, bent valves and engines still ran before teardown. But never have I seen where 1 cylinder has an over heating cycle when all other cylinders are not. If one cylinder is functioning in pre heating all are doing the same.
I just went and started my civi truck, 82, easiest to get at and start and the engine stopped running and the balancer stopped at the same spot on balancer 4 out of 5 times. I may uncover my CUCV and look at the result. Wet stop on that cylinder and burn the same starting. But why noone else has seen the same problem?
Wet test and dry can narrow down the symptoms to specific causes.
What I see as troubling as the glow plug is "melting" many glow plugs and the piston is not having any damage as well, melting at the ring land or cracking from too much fuel. I have always replaced any Wellmans with A/C Delco when I see them on trucks. The Delco glow plugs in my experience are the best you can use. I have Delco in my 82 civi that have been in there for over 25 years and still work fine. When I got the CUCV 1008 I took out the new wellmans and replaced with Delco's right away.
The melted pieces have to go somewhere, I have seen chewed up pistons, valves scared from glow plug pieces, bent valves and engines still ran before teardown. But never have I seen where 1 cylinder has an over heating cycle when all other cylinders are not. If one cylinder is functioning in pre heating all are doing the same.
I just went and started my civi truck, 82, easiest to get at and start and the engine stopped running and the balancer stopped at the same spot on balancer 4 out of 5 times. I may uncover my CUCV and look at the result. Wet stop on that cylinder and burn the same starting. But why noone else has seen the same problem?
Yeah. Switching the glow plug connector did not move the problem. The start box provides the same voltage to all the glow plugs.. all those are wired in parallel. What one plug gets, they all get unless the wire is broken, in which case that particular plug gets 0 volts. I also metered the glow plug connector to verify it was not continuously powering the glow plug. I pulled several of the other glow plugs out to make sure they were still operational and intact.. and now with the glow plug completely disconnected it's still swelling (and was damp with fuel) which suggests the issue is a matter of too much fuel in that cylinder.
Hopefully that settles your testicle twitch. If not, I find sitting on it for a bit helps.. at least until you get up and start walking around.
Well.. be careful suggesting Wellmans aren't the greatest glow plugs on Earth around here. I can hear the sharpening of pitchforks as I type this.
I'm going to retry my compression tests again this afternoon with ALL the glow plugs removed. My tests yesterday were through the injector hole but I was only removing injectors as I tested the cylinder.. that means the first cylinder was tested with all the other injectors still in place.. the second with only the adjacent injector removed, and the third with just the two injectors on the other side removed. I'll try the tests with all the glowplugs out so the only cylinder with compression should be the one I'm testing and the starter should be able to spin the engine quite a bit faster.. I'll see if that has any effect on my compression readings.
By "wet test" you mean put a little oil down into the injector hole and see if the compression improves to see if the low reading is due to worn piston rings?
I'll see if I can get a picture of it today. I'm going to repeat my compression testing and I'll get the scope out and give 'em another peek. I think I may be able to connect my scope to my laptop and grab images and I'll share those here in case something jumps out as off that I'm not seeing... mostly because I really only have a loose idea of what I'm supposed to be seeing to begin with.
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.Well.. be careful suggesting Wellmans aren't the greatest glow plugs on Earth around here. I can hear the sharpening of pitchforks as I type this.
I'm going to retry my compression tests again this afternoon with ALL the glow plugs removed. My tests yesterday were through the injector hole but I was only removing injectors as I tested the cylinder.. that means the first cylinder was tested with all the other injectors still in place.. the second with only the adjacent injector removed, and the third with just the two injectors on the other side removed. I'll try the tests with all the glowplugs out so the only cylinder with compression should be the one I'm testing and the starter should be able to spin the engine quite a bit faster.. I'll see if that has any effect on my compression readings.
By "wet test" you mean put a little oil down into the injector hole and see if the compression improves to see if the low reading is due to worn piston rings?
Yessir, wet testing means with a squirt of oil. Yeah, possible worn rings - but your problem doesn't really indicate that's the problem. Unless you tear it down and find a "crunch mark" on top of a piston on the side, I doubt it would be that close. Based on the readings you took earlier...
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Compression tests should be performed warm. The compression in the other cylinders should not affect the cylinder being checked. When you add oil for wet testing, only add a tiny bit. Too much and you will hydrolock and bend things.
Testing cold can give low numbers. Rings need to warm up and expand IIRC.
Best of luck
Compression in other cylinders shouldn't effect the compression in the cylinder being tested but it has been suggested that the additional drag on the starter motor would effect the speed in which the engine cranks over, and that could effect the amount of compression. Presumably you want the cylinder to move at a rate equivalent to idle or close.. but I've seen people say anything over 300 rpm is sufficient.
As to hot/cold compression testing if something bad is happening in this motor I didn't want it running any more than it needs to, although an argument could be made that whatever damage is already done. Ultimately I'm testing to find out how "bad" the cylinder is so testing in the least optimal manner would give me the worst case scenario. I'd think a warm engine would only increase the compression measurements.
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This is what I have on testing of the 6.2
Cheers
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Here's the easy story book on the above pages. Might be a bit easier on the eyes 
has some electrical in it too.
This thread is a doozie. I am waiting for the boogieman
with a little hammer 
to jump out of that cylinder.
Get a picture for Mogman, CAMO
has some electrical in it too.This thread is a doozie. I am waiting for the boogieman
with a little hammer to jump out of that cylinder.Get a picture for Mogman, CAMO
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At this point you are not trying to determine if the engine is worn out or not, the exact compression number is not as important as the difference between cylinders, yes it will be lower cold than if hot and you do not have the prescribed test equipment so you are not sure how much the setup you are using effects the actual reading or how accurate the gauge is.
But your setup should give you a relative difference between cylinders, and between adjacent cylinders.
The specs call for the lowest reading to be no more than 20% less than the highest, with the number you listed of 330PSI as the highest that would put the min at 264PSI
Interested in what the next round of tests show, I assume you would actually have to pull all the injectors because of your setup, you should check all of the cylinders.
But your setup should give you a relative difference between cylinders, and between adjacent cylinders.
The specs call for the lowest reading to be no more than 20% less than the highest, with the number you listed of 330PSI as the highest that would put the min at 264PSI
Interested in what the next round of tests show, I assume you would actually have to pull all the injectors because of your setup, you should check all of the cylinders.
That's actually one I had printed and bound.
Got back into it today with the inspection scope and found this .. what looks like a crack in the pre combustion chamber. How am I?
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I guess i was kinda right.
I don't like doing half repairs but i guess a machine shop should be able to replace the cup and rectify the heads.
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I corrected your grammar...
Actually cracked cups are common, there is a "standard" for how long the crack can be and still re-assemble the head, although that one looks pretty bad, you may have found the issue.
You can pull the head and have the cups replaced, there is an "updated" version I believe.
Good engines will have good compression regardless of temperature. Testing warm is more of a salesman gimmick to convince you to buy a weak engine. Especially in the case of a diesel engine good compression is most important when the engine is cold. Lower cranking speeds due to injectors in the hole or cold oil shouldn't have a huge impact on your compression number. If the number is lower during slow cranking it indicates leak down.
Testing an engine hot is like dumbing down the test so a bad student can pass it.
Testing an engine hot is like dumbing down the test so a bad student can pass it.