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1983 Jeep CJ 6 Cyl Smokes Badly

3K views 52 replies 10 participants last post by  vespaholic 
#1 · (Edited)
I'm new to this forum.
I just picked up a 1983 CJ with a 6 cylinder engine.
I'm trying to figure out what steps to take to figure out what it going on with it.
Any input would be appreciated.
First off the Jeep starts, runs and drives great.
This is my first CJ and it has more power than I thought it would have.
Mileage is 151K, but I have no knowledge of any possible rebuilds.
It smokes constantly at idle.
I think I smell gas in the oil.
The oil was recently changed (according to the prior owner) but is very black and seems very thin.
I pulled the PCV and it made no difference in the amount of smoke.
It needs a carb gasket for sure as it is sucking air at the base.
What has me stumped is the power that it has.
If the rings were bad and I was losing compression, I think it would be less powerful.
Thanks in advance!
Tony
 
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#2 ·
First, is the smoke black or white? If white, you have coolant leaking into your cylinders and it's getting burned. This is no bueno. If it's black:

I would start by making sure the carburetor is a-okay. It sounds like you are simply running rich. This might just be an adjustment problem, but it could also be a gasket problem. Many times when people are selling their CJ's, they haven't been driven in a while, and the carburetor might be gummed up or have dry rotted gaskets. I recommend you buy a rebuild/gasket kit, replace the gaskets, & clean everything with carb cleaner. If your not sure how to do this, throw up a picture of your carb/ tell us what it is, and I can help you find instructions.

I am a little concerned that you smell gas in the oil, and that is seems thin. I would still try the carburetor kit first.
 
#4 ·
Blowby is excessive crankcase vapor that escapes into the engine compartment, not the exhaust. It causes leaks in places like the valve cover gasket and grommets, oil filler cap, oil dipstick...basically any orifice on the block and heads.

If gas is getting into the oil, you should be able pull the dipstick and smell the fuel. Another test would be to change the oil. If the smoke goes away temporarily, but returns after a short while, then you have an internal fuel leak. The fuel pump diaphragm would be my first suspect.

Bad valve seals will usually cause smoke at startup that subsides as the engine heats up. Bad rings will cause smoke while accelerating.

Good luck,

Matt
 
#5 ·
@Matt@: Thanks for the reply.
The prior owner told me that he changed to oil then it stopped smoking for a while, later returning.
Yes, I did pull the dipstick and that's is how I smelled the fuel in the oil.
I'm going to swap the fuel pump today and change the oil, air filter and fuel filter.

Should I do anything else while I'm at it?

Will advise!
Thanks!
 
#6 ·
Update 12/4/16

Here's what I did today:

Changed the Oil & Filter
Changed the Air & Fuel Filters
Swapped out the Fuel Pump
New Cap/Rotor/Wires/Plugs
Removed the Valve Cover - Clean as a whistle inside.

Here's what I found!
All the plugs EXCEPT ONE looked a perfect golden brown.
No soot, oil....Nothing!

That is except for the #3 Spark Plug.
It was sooty (black) and fouled, but I would not call it wet.

Still blows constant blue smoke.
A little less, but it was dark by the time I was finished so I'm not 100% it was less; I'll try again tomorrow.

I guess I feel better that it appears to be a problem with only one cylinder.

I'm going to rebuild the carburetor because I still think its dumping too much gas.

Any other suggestions??

Thanks again!
 
#9 ·
He meant for you to just swap one wire and or plug from another cylinder to eliminate the possibility of having a bad wire or plug that would foul on another cylinder then #3.
 
#10 ·
What Keith said. ^^^^^

If it's not a bad plug or plug wire at fault, you may have to pull the valve cover, again, and look for a sticking valve, or bad lifter in the #3 cylinder.

Coincidentally, about a year ago, the #3 cylinder on my 360 started fouling the plug. The pic below is what I found when I pulled the valve cover. The pushrod had poked straight thru the rocker. Fortunately, it was just a defective rocker, and was a quick and easy fix.

Keep us posted,

Matt
 

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#11 ·
@Matt: Fortunately, nothing was poking through like that.
I was surprised how nice it looked under the valve cover.
No sludge at all, everything nice and clean.
What's the procedure for checking for a sticking valve or bad lifter?
I'll look for a video on youtube as well.

Could a bad computer be the issue?
I was thinking of doing a Nutter and also tearing out all the smog stuff.
This is the newest old car I have and I was overwhelmed by all the crap under the hood.
 
#12 ·
@Matt:
What's the procedure for checking for a sticking valve or bad lifter?
I'll look for a video on youtube as well.

Could a bad computer be the issue?
A leak-down test would confirm a sticking valve. Alternatively, you could simply watch the valve train movement while a helper cranks over the engine (disconnect coil, so the engine doesn't fire). The valves springs should all move up and down the same distance in a rhythmic sequence. If one doesn't move, chatters, or moves irregularly, then that's the culprit valve, lifter, or cam lobe.

I *think* a bad computer would cause more general problems to all cylinders, not just one. That said, if you aren't required to pass emission testing, the Nutter bypass would eliminate a lot of troublesome emissions crap, and tidy up your engine compartment a bunch.

Matt
 
#16 ·
Depending on how bad your valve seals are, they may not seal up when the motor warms up. Had a 304 that would smoke horribly at idle after driving for long distances until I finally got the heads rebuilt and new seals installed. Smoked enough that you would lose sight of the silver colored Wagoneer in the cloud after about 15 minutes.
 
#17 ·
@JoonHoss: Good idea. I'll worry about the cosmetics after I get it running right.
@Fourtrail: I'll hope that's not the case.

I'll see how it runs with the new plugs and wires.
Hopefully one of the old ones was bad.

I'm going to pull the valve cover again and inspect the valve train in operation, running it with the cover of.
Hopefully I'll be able to see whats going on with the #3 cylinder.

Again, all the others look great! It's just #3 that fouled the plug and appears to be letting the oil through to burn.
 
#18 ·
@JoonHoss: Good idea. I'll worry about the cosmetics after I get it running right.

@Fourtrail: I'll hope that's not the case.

I'll see how it runs with the new plugs and wires.
Hopefully one of the old ones was bad.

I'm going to pull the valve cover again and inspect the valve train in operation, running it with the cover of.
Hopefully I'll be able to see whats going on with the #3 cylinder.

Again, all the others look great! It's just #3 that fouled the plug and appears to be letting the oil through to burn.
Valve seals are fairly easy to change so if that is all it is, then it shouldn't be a big deal. Compare the seal inside of the springs on #3 to the rest of the cylinders. It should be fairly obvious is they are bad.
 
#19 · (Edited)
Update: 12/5/16

When I got home from work I started the Jeep up and let it run for a long while in my driveway.
Smoked like a mother!
Went for a drive and it sputtered and popped and backfired so I turned back for home.
Pulled the #3 spark plug and it was oily wet and fouled badly.
I checked the other plugs and they were perfect.
Put another plug in #3, went for a drive.
I got a little farther, then it started sputtering and backfired etc...
Got it back home.
#3 was fouled and oily again.

Pulled the valve cover.

@Fourtrail: I looked into the valve springs to see if there was a noticeable difference.
Truth be told....I'm not sure what I'm looking at/for.
Can you please advise?

I just went back out and looked agin into the valve springs.
There is a white "cap" within the spring that is on the valve stem.
It appears to be the same in all the valve springs.
They seemed high on the valve stem.
Should they be pushed down??

Thanks advance!
Tony
 
#20 ·
Do you have a Factory Service Manual. If not, you should have.

Below illustrates the components of the valve train. The FSM calls the valve seals "oil deflectors". They prevent oil from draining into cylinders thru the valve guides. They are nylon, and should be replaced any time the valve springs come off. At 151K original miles, it's likely the #3 cylinder deflectors aren't doing their job.

Matt
 

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#21 ·
@Matt: I agree about the service manual; I'll do that.
Also, thanks for the picture.
The Deflectors all looked the same within all the valve springs.
I did notice that the deflectors on #3 were farther towards the top of the valve stem than the others.
Looked like they were stuck up there.
I pushed on them with the side of a flat head screw driver and they felt like they were stuck up there.
They bottomed out easily after the initial push.
 
#22 ·
vespaholic said:
@Matt: I agree about the service manual; I'll do that. Also, thanks for the picture. The Deflectors all looked the same within all the valve springs. I did notice that the deflectors on #3 were farther towards the top of the valve stem than the others. Looked like they were stuck up there. I pushed on them with the side of a flat head screw driver and they felt like they were stuck up there. They bottomed out easily after the initial push.
We may be getting somewhere. IIRC, those deflectors should slide freely on the valve stem. If they stick on the stem they won't seal the valve guide.

Matt
 
#23 ·
@Matt: That's good to hear.
I'll hit them all with some PB blaster and push them down (up isn't an option) and see what happens.
I'll report tomorrow.

BTW: I appreciate the help and comments here.
My primary reason for buying this Jeep was to put a plow on it so I can do my driveway.
I've already sold my truck with a plow.
Well....winter is coming fast here in PA and I do not want to order a plow for a Jeep that does not run right.
Hence, the lazy man's approach to asking questions here vs. getting the manual and figuring it out.
I find that forums like this are a much better resource for a novice!
I thank you for the help!!!
Tony
 
#24 ·
Well, I was wrong. The oil deflectors used on your engine are the "umbrella" type. They are suppose to move up and down with the valve, not stay seated on the guide. Later "positive" type seals remain fixed to the top of the guide.

Sooooo....don't attempt to free the deflectors from the valve stems.

Your factory cam has about 1/4" of lobe lift. So that's roughly how far up the stem the deflector should ride. It couldn't hurt to replace the deflectors, but unless they are crumbling apart, I'm afraid they may not be your problem.

Matt
 
#28 ·
A compression check may, or may not, tell the story. Cam lobe wear, for example, won't necessarily show up on a compression check.

I think the OP should step back to basics. This is the order in which I'd start diagnosing.

1. Determine if #3 cylinder is getting good spark. Use a new plug for this test. I won't go into the "how to" since that has been covered countless times. If there's good spark, we can eliminate the ignition. If not, we can go from there.

2. Assuming good spark in #3, I'd focus on the valve train, specifically lobe lift. All the valves should travel up and down the same amount when the crank turns over. You can measure lobe lift using a dial indicator on the pushrods, or as I stated earlier, you can carefully watch the #3 valves, while the engine is cranking, to see if they move up and down the same amount as the other cylinders. If the lobe lift checks out, then the cam, lifters, springs, and pushrods are probably fine. If not, you'll have pull the head and determine which of those things is the culprit.

3. If the lobe lift checks out OK, I'd start to suspect a burnt valve. Here's where a compression, or leak-down test would be helpful.

If that doesn't pinpoint the problem, then I'm fresh out of ideas. There are only a handful of things that can cause a dead hole.

Matt
 
#29 ·
They way I typically would check for good spark would be to hold a wired spark plug so as to ground it to the block.
Then crank the engine.
Blue = Good Spark
Yellow = Weak
So I'll do that first.

If I have spark, then I'll throw a level across the top of the rockers to give myself a good visual point as to the uniformity of the movement.

If that looks good I'll order the compression test kit.

Will advise.

Thanks!
 
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