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Unread 08-10-2014, 07:14 AM   #1
Sherms-CJ7
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Engine compromised by bad spark plug

Can't believe this happened. Low mileage engine and troubleshooting oil in air cleaner, so I was doing compression checks and was hoping to find out it wasn't blow-by ... and this is what I found checking #5 cylinder when I pulled the spark plug ...
img_5995_small.jpg

And, yep, there was oil on that plug and compression in that cylinder was low. Thinking I'll change oil and using a heavier weight to see if I can get some more life out of it. Debating just biting the bullet and changing out the engine or pulling the head and oil pan, honing the cylinder, and replacing rings and bearings of affected piston? What do you think? Any help or advice will be greatly appreciated.

Thanks -
John

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Unread 08-10-2014, 07:27 AM   #2
keith460
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Could have been oil and fuel buildup in the cylinder that didn't get burned due to the looks of that spark plug. I think I would at least remove the cylinder head and check the condition of the valves to make sure they are not chipped or edges broken causing low compression test.

Did the compression rise a little if you squirt oil in the spark plug hole or was their little to no difference?
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Unread 08-10-2014, 07:52 AM   #3
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DON'T PANIC!

You wouldn't believe what shows up in the shop in cylinders with the engine running fine!

First off, the cylinder wasn't firing CORRECTLY when the electrode came off the plug,
So chances are 9 out of 10 it went right out the exhaust valve and is now making a little rattle in your muffler!

Secondly, even if it did manage to stay in the cylinder, there is a whole lot of surface area in the center of the piston for it to stick to!
If you don't run super lean fuel mix, this thing will never get hot enough to have that little bitty piece of metal get hot enough to melt through the piston.
*IF* it's still in the cylinder, and that is HUGE 'IF'... It's probably got a 'Lazy Boy' position on the piston somewhere just riding along doing nothing...

THIRD!
DO A COMPRESSION TEST... BOTH WET AND DRY.
This will tell you right away if the 'Worst' happened.

IF you still get a low reading 'Wet', then do a leak down test...

The 'Worst' could be (But 99/100 didn't happen), welded or hammered into valve seat or bent a valve.
Compression test will show that up right away.

Got between piston and cylinder wall and galled the cylinder.
Again, compression test or leak down test will show that up right away...

If you have reasonable compression, it's gone and didn't cause any problems. No issues other than a new plug, one with the correct lenght this time,
And set your timing so you don't detonate and you should be fine.

-------------

Two things to remember,

1. This cylinder hasn't been firing CORRECTLY for a while so the carbon has built up on rings, valves, in the combustion chamber.
Don't expect factory new compression readings, but it should be within the 20% range of the others.

2. The 'Oil' isn't.
Oil control rings on the piston DO NOT remove all oil from the cylinder. That's a myth...
The rings leave a very thin layer of oil on the cylinder walls to lubricate the piston and rings.
Under 'Normal' conditions, that oil film is burned away at proper combustion temps, which you didn't have, so you have semi-liquid carbon,
Not exactly oil, not exactly carbon, but something in between,

The point is, Don't automatically ASSUME that little tab wiped out the cylinder, rings, piston, valves, ect. and that is the reason for the oil in the cylinder...
Do your testing with a compression gauge...

I would probably put a good plug in and run the engine a little bit, at least drive it around a little at highway speeds to burn off/blow out that sludge,
Then I would do a compression test...

-----------

This has nothing to do with your situation,
We have found nuts, washers, entire center electrodes from spark plugs, (sheet metal) air cleaner wing nuts, a self tapping metal screw and other stuff in engines that ran tons of miles AFTER the FOD showed up. (FOD = Foreign Object Damage)
Melted or was punched right into the top of the piston, or flattened out and carbon welded it to the piston top and the engine ran fine for long miles afterwards...

In older engines, when spark plug technology wasn't what it is today,
And back when people screwed with their own timing regularly,
We would find the ground electrode of the plug all the time, just stuck in the top of the piston in 150,000 or 200,000 mile engines.

Another note,
I would have a VERY close look at that cylinder...
If something other than a faulty plug caused this you need to find it.

The most common is detonation. Cylinder too lean.
1. VACUUM LEAK to that cylinder.
2. Engine 'Knocking' (spark knock), 'Pinging', or 'Hesitation' under load at part throttle cruise, when fuel is leanest and load is highest in high gear.
3. Wrong length plug.
4. Working the ground electrode excessively when gaping plugs are all common causes of ground electrode failure.
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Unread 08-10-2014, 07:54 AM   #4
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Just a heads up, carb engines font run well on Bosch platinum plugs, the plugs are too cold and don't fire right.

I also lost #5. But mine had extreme blow by when mine went out. Could watch my plastic valve cover balloon out bad. Well worth doing a second compression test with a squirt of oil in the cylinder first to see if it is rings or valves.

Yours might just be carboned up from not firing too.

I have seen single cylinder fixes like you want to do that worked for a ring issue. I found a good low mileage 4.0 for $100.00 delivered, so just swapped it in and put all my 258 stuff on it. $50.00 for a pump and $50.00 for exhaust work and I was on the road again real quick.
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Unread 08-10-2014, 08:05 AM   #5
Sherms-CJ7
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Hey Keith,

I was thinking that the end of the spark plug broke off and damaged the rings/ cylinder wall.

And yes - just checked and after adding oil, the pressure jumps up significantly ... 90 psi to 200 psi.

Sorry - stupidity here, but I hadn't actually done compression checks until yesterday. Hope I'm doing it correctly? Will letting it crank over too much cause pressure to read higher than it should? Well, it should be fine ... when I saw how low that one was initially, I let it crank over a bit more anyway just to be sure. To give you an idea of the initial (almost) full compression check:
#1 175 psi
#2 180 psi
#3 160 psi
#4 150 psi
#5 90 psi
#6 not measured yet

As always - thanks much for all your help!!
John
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Unread 08-10-2014, 08:12 AM   #6
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Quote:
Originally Posted by Sherms-CJ7 View Post
Will letting it crank over too much cause pressure to read higher than it should?
No, it will only reach a certain pressure until leaks or the combustion chamber volume limit how high it can possibly go. But it does sound like you have something going on with the rings or piston of that one cylinder.
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Unread 08-10-2014, 09:46 AM   #7
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You guys are awesome - Thank You so much for all the help and info!! However, as the pressure came up significantly, I'm thinking I might have the unfortunate situation of damage to rings/cylinder wall, though I'm not sure about valve damage etc. Also, as Jeephammer had referenced the poor condition of the spark plug, I thought I'd post better pics of the electrode ... from the looks of it (in pics where flash was used), I was almost thinking it had been firing ... ?

img_5989_small.jpg

img_5990_small.jpg

img_5991_small.jpg

So, some follow on questions ... What brand of spark plugs are recommended? I wouldn't have thought it made much of a difference, but I'm now very skeptical. Also, was the first pic misleading, i.e. is there really any carbon build-up? I didn't think so, but would love to be wrong. If there is carbon build-up, then I was initially considering running with Marvel Mystery oil for 300 miles or so and then changing the oil. Is this a good idea given my situation ... to clean the engine of build-up etc.? I am thinking that I want to drive some, probably with a heavy weight oil, before doing tear down to fix piston/cylinder, but only if this won't make matters worse?

Also, don't know if this amusing, stupid or what, but I put a magnet into the cylinder to try to fish out any metal that might have been left behind. Found some small amount of particulates, though they didn't seem significant ... then again, aren't any particulates bad? BTW, Jeephammer ... I very much know what FOD is Back in the 90's, I was in the Navy and my squadron would get together some mornings and do a FOD walkdown of the flight line. It was actually around that time that I bought my Jeep.

Thank you very much again!!
John
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Unread 08-10-2014, 12:52 PM   #8
Sherms-CJ7
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Some searching and I found answers to question of which brand of spark plugs ...

http://www.jeepforum.com/forum/f8/be...plugs-1138361/

http://www.jeepforum.com/forum/f8/e3...plugs-1572638/

And still love to hear thoughts on running with Marvel Mystery Oil to clean 'er out?

Best regards -
John
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Unread 08-10-2014, 01:55 PM   #9
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I'd run a leak down on it and see if you can hear air coming out the exhaust. That electrode may not have made a clean escape through the exhaust valve. Hell, you really don't even need a leak down gauge for this. You just need to pressurize the cylinder at TDC and listen to the exhaust.


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Unread 08-10-2014, 02:54 PM   #10
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Quote:
Originally Posted by swatson454 View Post
I'd run a leak down on it and see if you can hear air coming out the exhaust. That electrode may not have made a clean escape through the exhaust valve. Hell, you really don't even need a leak down gauge for this. You just need to pressurize the cylinder at TDC and listen to the exhaust.
Shawn
Hey Shawn,
Thanks much for the advice. Actually,I recently had to replace the catalytic converter, which was whistling and causing power loss. Wondering if that little negative electrode piece was the culprit?
Thanks again -
John
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Unread 08-10-2014, 05:11 PM   #11
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Actually, as I just mentioned the failure of the catalytic converter (couple of weeks ago), that actually occurred immediately after the ICM and coil failed? Is it all possible that the ICM/coil failed in such a way that it damaged the spark plug causing the negative electrode to crack and fall apart? I don't see how that could be so, but ... hey, I wouldn't have thought a spark plug even had such a failure mode?

Thanks for all your help -
John
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Unread 08-10-2014, 05:20 PM   #12
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Nope, cat converter usually falls apart internally, or it plugs up. Electrode wouldn't have anything to do with it.

Now, on to the issue at hand...

Put some REASONABLE plugs in, more expensive or 'Super Duper' plugs not wanted or needed, just the usual $2 each plugs from Motorcraft/Autolite.

DO NOT pry on the center electrode when you gap them, use a gaping tool that grips the ground electrode,
And DO NOT bang the plug on something to close up the gap!

Plugs, especially carbon core resistor plugs, are very sensitive to shock, so if you drop one putting it in, leave it on the floor! Not worth $2 to loose 1/6 of your fuel or power.

Go out and run the thing on the highway, get it good and warm under part throttle cruise when fuel is leanist and that will burn off/blow out most of the 'Gunk' in the cylinder...

Once that is done, do your compression test again.
If it's just gunk in the rings, running it at full temp a little lean will cook that crap out,
Same with carbon deposits on the valves/valve seats...

There isn't anything you can do right now about the gunk that has formed on the back side of the valves, but you can do something about it if the engine proves sound...
You can steam clean your cylinders by running the RPM up on a well warmed engine, then trickling water or water/alcohol mix down the carb...
You won't want to have ANYTHING you like around the tail pipe since it's going to get coated with a large amount of black gunk, and that includes the driveway...
But all that gunk is carbon deposits that were on the valves, in the head, on the piston/rings and in the exhaust...

Now, since you HAVE compression, the issue isn't major... YET...

If you turn the cylinder over to TDC of compression, and you will have to be fairly precise about getting TDC (piston all the way up),
And chalk the tires, in gear, brakes set...
Then add shop air to that cylinder you will VERY quickly know where your compression is going!

If you hear air coming out of the PCV valve, it's blow by the piston/rings leaking.
If you hear air coming out of the intake/Carb, it's the intake valve leaking.
If you hear air coming out of the exhaust it's the exhaust valve leaking...

To be quite frank, with 120 to 180 PSI shop air on most everyone's engines, you will hear some amount from all three, so again, don't panic!
Older, high mileage engines have a tendency to leak, it's a fact of life...
Everyone *THINKS* because they have 'Good' compression on a gauge everything is sealed up tight, but it couldn't be farther from the truth...

Valve guides wear letting the valve move around and slap the sides of the seats causing out of round conditions, and the valves leak.
There are gaps in ALL piston rings, some smaller than others, but they all leak past the pistons...
It's just a fact of life...

Compression gauges give you PEAK pressure, not the ability to watch how fast that pressure leaks off,
That is what a leak down test is for.
Leak down test will shoot a MEASURED amount of air into the cylinder and you watch a gauge...
Lower the pressure, the more is leaking out very quickly and that is the standard you use to tell if it's time for a rebuild or not when one is low but not completely failed.

Also, if push comes to shove, getting the head off will tell you right away if it's going to be a 'Glaze Bust' hone and new rings or a full piston replacement,
And/Or the valves have seen better days and need to be replaced.

When you start talking about full on engine rebuild, you are talking about serious money and time, so do a little cleaning/testing and make sure you need to get that far into this thing, and know exactly what is wrong before you start buying parts or taking things apart if possible...

---------------
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Unread 08-10-2014, 05:33 PM   #13
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Quote:
Originally Posted by JeepHammer View Post
Nope, cat converter usually falls apart internally, or it plugs up. Electrode wouldn't have anything to do with it.

Now, on to the issue at hand...

Put some REASONABLE plugs in, more expensive or 'Super Duper' plugs not wanted or needed, just the usual $2 each plugs from Motorcraft/Autolite.

DO NOT pry on the center electrode when you gap them, use a gaping tool that grips the ground electrode,
And DO NOT bang the plug on something to close up the gap!

Plugs, especially carbon core resistor plugs, are very sensitive to shock, so if you drop one putting it in, leave it on the floor! Not worth $2 to loose 1/6 of your fuel or power.

Go out and run the thing on the highway, get it good and warm under part throttle cruise when fuel is leanist and that will burn off/blow out most of the 'Gunk' in the cylinder...

Once that is done, do your compression test again.
If it's just gunk in the rings, running it at full temp a little lean will cook that crap out,
Same with carbon deposits on the valves/valve seats...

There isn't anything you can do right now about the gunk that has formed on the back side of the valves, but you can do something about it if the engine proves sound...
You can steam clean your cylinders by running the RPM up on a well warmed engine, then trickling water or water/alcohol mix down the carb...
You won't want to have ANYTHING you like around the tail pipe since it's going to get coated with a large amount of black gunk, and that includes the driveway...
But all that gunk is carbon deposits that were on the valves, in the head, on the piston/rings and in the exhaust...

Now, since you HAVE compression, the issue isn't major... YET...

If you turn the cylinder over to TDC of compression, and you will have to be fairly precise about getting TDC (piston all the way up),
And chalk the tires, in gear, brakes set...
Then add shop air to that cylinder you will VERY quickly know where your compression is going!

If you hear air coming out of the PCV valve, it's blow by the piston/rings leaking.
If you hear air coming out of the intake/Carb, it's the intake valve leaking.
If you hear air coming out of the exhaust it's the exhaust valve leaking...

To be quite frank, with 120 to 180 PSI shop air on most everyone's engines, you will hear some amount from all three, so again, don't panic!
Older, high mileage engines have a tendency to leak, it's a fact of life...
Everyone *THINKS* because they have 'Good' compression on a gauge everything is sealed up tight, but it couldn't be farther from the truth...

Valve guides wear letting the valve move around and slap the sides of the seats causing out of round conditions, and the valves leak.
There are gaps in ALL piston rings, some smaller than others, but they all leak past the pistons...
It's just a fact of life...

Compression gauges give you PEAK pressure, not the ability to watch how fast that pressure leaks off,
That is what a leak down test is for.
Leak down test will shoot a MEASURED amount of air into the cylinder and you watch a gauge...
Lower the pressure, the more is leaking out very quickly and that is the standard you use to tell if it's time for a rebuild or not when one is low but not completely failed.

Also, if push comes to shove, getting the head off will tell you right away if it's going to be a 'Glaze Bust' hone and new rings or a full piston replacement,
And/Or the valves have seen better days and need to be replaced.

When you start talking about full on engine rebuild, you are talking about serious money and time, so do a little cleaning/testing and make sure you need to get that far into this thing, and know exactly what is wrong before you start buying parts or taking things apart if possible...

---------------
Hey Jeephammer!

Wow - Thank You much ... I was looking forward to your answers and, as usual, you did not disappoint, though I wish you had better news

Before reading your reply ...
At this point, I'm changing the oil to put in heavier 10W40 ... and am changing out the plugs ... swapping out all Bosch for Autolite 985 (copper). Hoping I can run it for a little while. Still debating if I should throw a quart of Marvel Mystery Oil in there and change the oil again in 300 miles? Was really wondering if I should try running it for a time with 20W50? And, the answer is probably that I should park it in the garage and should pull the head and assess the damage?


Now...
So, if I'm understanding you, I can and should run it for a short time before doing another compression check. And then should do a full on leak down check. One thing to clarify after your response - very sadly, this engine only has like 5k miles on it, if that much ... don't know if that changes anything about your thoughts on what I should do ... ? And, you haven't mentioned anything about the Marvel Mystery Oil thing, so I'm thinking you wouldn't advise that course of action?

Thank you again so much - you are incredibly helpful and I just can't thank you enough ...


John
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Unread 08-10-2014, 05:48 PM   #14
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You'd be amazed at how well a good cat can act as a filter before the turbo. Yeah, we found the exhaust valve and chunks of cylinder sleeve packed up at the converter.



Again, let's find out if you're leaking pressure through one of the valve seats.


Shawn
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Unread 08-10-2014, 06:30 PM   #15
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I agree with Shawn, but the order I would change...

Since the engine IS RUNNING NOW, and you have LOW COMPRESSION, but you have runable compression, I would run the engine to clean it out some before I made final determination.
As part of the diagnostic process...

Clean (or cleaner parts) will give you a good idea of what things are actually doing.
Right now, you have that same gunk you found on the plugs packed into the oil control ring set, and you have that gunk pressing on the compression rings...

It's also on the valves.
If it carbonized on the valve seats, that will show up as a valve seal leak and might prompt you to pull the head right away when all it needs is cleaned out,
And the high end of standard running temps will clean a bunch of that crap out.
So cleaning it out will give you a better idea of what damage, and how much damage you have.

Cylinders not firing is HORRIBLE on them,
The rings get packed full of partly carbonized oil, the valves get carbon on the back sides of them and it runs down into the valve seat when it's like you have now.

Clean that crap out,
The heat will bake on the carbon that is attached, and it's inert then,
Or it will clean off and blow out the carbon/burned oil so it doesn't get in the way of accurate testing when you do a leak down test,
Or when you pressurize the cylinder and listen for leaks...

If it were me, I'd go out and run 1/2 hour on the highway at steady, part throttle cruise, then bring it home and do the water down the carb thing (or along side the road or convince store where the carbon sludge wouldn't screw up my driveway!) and then go home, let it cool down and have a test of that compression again,

Since most people don't have a leak down tester (and most probably haven't heard of one) you will have to take it to a shop or rent one for the test, and this will give you time to research the leak down tester and see how it works...

Like I said, if you can keep it from running over you (Piston at TDC, wheels chocked, brakes on, vehicle in REVERSE so it doesn't run over you if the piston isn't at TDC and decides to turn the crank)...

Apply shop air to the cylinder through the spark plug hole and listen...

You will hear blow by the piston, usually at the PCV valve. This is normal, but excessive blow by will tell you the rings are not doing their job...

You SHOULD NOT hear air escaping into the intake.
If you do, the intake valve is the issue.

You should NOT hear air escaping into the exhaust.
If you do, that means the exhaust valve isn't sealing.

-----------------

Now, my way of practical thinking here is,
You have been driving this thing a while with the plug broken...
Now driving it another 1/2 hour isn't going to make the engine look like Shawn's picture, and it's not going to cause any more damage than you have now...

If that electrode is still around in the cylinder, it's welded or bonded to something by now...
And it's just a question of WHAT it bonded to.

If it's bonded to the side of the piston in the compression ring groove there could be one hell of a gouge in the cylinder wall.
This would be the WORST CASE that could happen.

Most times it flies out the exhaust valve will no damage.

After that it might have nicked the exhaust valve seat on the way out,
This *COULD* cause the low compression you are seeing...
(I suspect gunk in the rings causing low compression, but if you don't blow/clean it out you won't know that before you take the piston out and manually clean it)

After that it might have got cough between exhaust valve and seat, bending valve and dinging the seat.
I don't suspect that since you can generate 90 psi of compression.
Bent valves usually generate less than half that compression reading.

After that the electrode might be harmlessly stuck to the top of the piston.
Now, this can cause issues *IF* you run super lean/super hot...
That electrode can glow and cause pre-ignition of intake charge, it can get overheated and melt through the piston head entirely...

BUT, keep in mind that you are running a overly rich Jeep engine at low RPM so the likelihood of you ever getting lean enough or hot enough for that electrode to cause problems *IF IT'S EVEN ON THE PISTON" is very small...

I'm not about to tell you what to do, it's your vehicle.

What I would do is run it up to burn off the excess carbon/oil/fuel deposits,
I'd steam clean the cylinders (Good for ANY overly rich or high mileage engine),
And I'd do some further testing to see exactly where the compression is going...

--------------

Now here is something that is from PRACTICAL experience,

You have to do failure analysis on what caused that electrode to separate...

1. Bad Electrode from the factory?
2.Or plug dropped or hammered on, if not by you but the shipping process or mutts at the parts stores?
3. Vacuum leak causing cylinder to lean out and detonate?
4. Bad lifter/rocker arm/push rod not getting fuel/air charge into the cylinder and getting detonation?
(Remember, bad valve lift will limit your compression also... Valve don't open, mixture can't get in to be compressed in the first place)

Anyway, I'd have a look at valve lift, see if the rockers on #5 are moving about the same as the rest of the cylinders,
I'd have a look at intake, especially around #5 to see if a vacuum plug has come out, vacuum line off somewhere, leaking gasket at the head, cracks in the intake if you have the cast version, ect.

All this is MUCH easier to do than pulling the head off and/or pulling the rod/piston and will tell you what to expect and what you can rule out.
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