Compression Test Results & Spark Plug Readings:

'90 Renix 4.0 ~36K on Reman.

The first time I ran a dry test, the numbers just kept dropping as I worked my way to the back. I figured out that the weak excuse for a battery was draining, so I jumpered it to my other car and kept it running. So, the voltage may've been a bit higher than standard, but it should be consistent for all cylinders.

Compression Test:
Cyl: 1 2 3 4 5 6
Dry: 130 120 140 135 100 110
Wet: 150 155 150 150 135 150

I added about 8mL of 10w30 to the cylinder for the wet test. When I started it back up, it was blowing pretty much the exact same shade of smoke as it does when it's smoking under regular use.

Ok, here are the splug plug pictures. Looks like #5 does have some sort of difference on the firing tip:






Does anyone have any insight here? I read up on some of the 'reading your spark plugs' pages, and for the most part I think they look ok. 1 looks a little heavy on the carbon buildup, and 5 has something going on at the tip. I'd be really interested to hear what anyone that has a bit more experience in reading them has to say. And what about those compression numbers? 5th cylinder looks weak, and the wet test bumped it 35psi. That hints towards blown rings, right? I'm going to try and put a compressor into the spark plug fittings to listen for air leakage today. First order of business is to Seafoam the intake and crankcase, then change oil and pull valve cover and clean CCV.
So, ideas? Thanks.

EDIT: Oh, and these plugs only have about 200 miles on them. Yeah, the threads are nasty on some of them. I need to try and vacuum out the plug hole areas or otherwise clean them. I noticed that some of the threads feel a little bit crossthreaded when putting them back in. Some didn't want to rotate nearly as many turns before going hand-tight. I guess I need to chase those threads, but I imagine that I need to clean the area first.

Other than just oil burning, could some of your injectors be leaking fuel, running it rich enough to make all those carbon deposits? Too much gas would also wash the oil off the piston rings and lower the dry test results right?

Mike McGinness
South Houston, Tx

Looks like you've got worn piston rings with the no.2, 5, and 6 cylinders being the worst affected.
You could run some seafoam through the throttle body to clean out the carbon deposits from the combustion chambers and try a can of Restore in the crankcase.
While your engine's not in perfect order, I think you've still got a few thousand miles left in it before you'll need to rebuild it. If you can't wait that long, start gathering parts to build a stroker and do the build when you're ready.

Well, I'm running the Seafoam through it right now. I'm going to run another compression test in the near future, so I'll be interested to see if the Seafoam has made any difference.
When I was under the engine checking for loose manifold bolts, I believe I saw a head gasket leak. That part of the engine exterior is still pretty nasty, so it could be old, but I saw some wet crud and I did see a single drop of coolant hanging out on a low bolt. The drop was around what I'd estimate is the gap between the 4th and 5th cylinder, and the wet crud goes all the way back. That could be either a head gasket leak all the way from 4 back, or regular old fluid travel due to the car moving. I thought I had fixed my coolant leak, but I have noticed some coolant dropping from right behind the passenger door, coming out of the rear upper control arm joint. It looks like the coolant is traveling through the unibody? But, I can't figure out where the source is. No wet passenger floorboard to suggest a heater core leak.

Dr. Dyno said:

Looks like you've got worn piston rings with the no.2, 5, and 6 cylinders being the worst affected.
You could run some seafoam through the throttle body to clean out the carbon deposits from the combustion chambers and try a can of Restore in the crankcase.
While your engine's not in perfect order, I think you've still got a few thousand miles left in it before you'll need to rebuild it. If you can't wait that long, start gathering parts to build a stroker and do the build when you're ready.

Click to expand...

I don't have any restore, but I'm going to be running a mix of 10W30, a quart or 2 of 10W40, and a quart of Lucas oil. I haven't decided on the exact mix yet, but I guess I'll be doing so pretty soon.

Oh, and I'm hoping that the Seafoam/Lucas will help it to stop pouring smoke out of the tailpipe. It'll never pass inspection in its' current state.

If this is what it looks like after 36K, I think you need to call whoever did it and show them these results.

ENGINE COMPRESSION
Check compression pressure with engine at normal operating
temperature, all spark plugs removed, throttle and choke valves wide
open and engine at cranking speed.
COMPRESSION SPECIFICATIONS TABLE

Application Specification
Compression Ratio .................................. 9.2:1
Compression Pressure ....... 120-150 psi (8.4-10.5 kg/cm 
Maximum Variation Between Cylinders .. 30 psi (2.1 kg/cm 

Saudade said:

If this is what it looks like after 36K, I think you need to call whoever did it and show them these results.

ENGINE COMPRESSION
Check compression pressure with engine at normal operating
temperature, all spark plugs removed, throttle and choke valves wide
open and engine at cranking speed.
COMPRESSION SPECIFICATIONS TABLE

Application Specification
Compression Ratio .................................. 9.2:1
Compression Pressure ....... 120-150 psi (8.4-10.5 kg/cm 
Maximum Variation Between Cylinders .. 30 psi (2.1 kg/cm 

Click to expand...

Oh, yeah I left that part out. I did get it up to operating temp and a with the throttle jammed at WOT.

And who would I be calling? The shop that sold and installed the motor 2 owners ago (12/2001)? I'd think their hands would be all washed of any responsibility by now. Or the guy I bought it from that said it was a NEW motor with 32K (not that the reman versus new should make a big difference)? He claimed that fluids had been well maintained, though I found out it was 3 quarts low after I drove from his house to the gas station to get gas and roadside emergency supplies. And truthfully, I don't even know the exact mileage as the speedo is off ~5mph due to the 30x9.5's, so I'd assume the odometer would be off as well. Regardless, I only paid $700 for it so I expected a project. I know that I wouldn't have gone all the way from Virginia to Pennsylvania for it had I known the true condition of the engine, though. I might be lucky that it made it back, dropping oil all the way.
Anyway, back to the purpose of the thread:
Any other ideas or clues that anyone is seeing here?

Obviously, you have issues in cylinders 3,5, and 6. The fact that all but #5 came into specs with the injected oil, I'd guess the very least would be worn rings, and possibly broken rings in #5. If there are broken rings, you stand a good chance of putting grooves in the cylinder wall that may be beyond a normal re-bore. If you intend on keeping this Jeep, I'd pull the head and inspect the cylinders. Doing a ring job is not that hard in the Jeep--if you know what your doing, and well, if you don't, now's a good time to learn.

xjbubba said:

Obviously, you have issues in cylinders 3,5, and 6. The fact that all but #5 came into specs with the injected oil, I'd guess the very least would be worn rings, and possibly broken rings in #5. If there are broken rings, you stand a good chance of putting grooves in the cylinder wall that may be beyond a normal re-bore. If you intend on keeping this Jeep, I'd pull the head and inspect the cylinders. Doing a ring job is not that hard in the Jeep--if you know what your doing, and well, if you don't, now's a good time to learn.

Click to expand...

Yep. I've never put rings on a piston before, but with the blown headgasket as well, I may soon be popping the top to find out how bad things are. I guess to find out if it's even worth putting back together, as well. I'm meeting up with the local Jeep guru tomorrow, so I'm hoping to see if he has an engine to spare.


Meanwhile:


Seafoam happened.



And I believe I may have located my exhaust leak up near the manifolds.



But, it's a good thing that there aren't any exhaust leaks into the passenger cabin.

I suspect there will be some angle grinding, sheet metal drilling, riveting, and probably some herculiner in my near future.

Whether or not the carpet will make a reappearance is kind of up in the air.


Unfortunately, I've got to make a 430 mile round trip for the Christmas holiday. If there's a broken ring, I imagine it'll do some good carving in that time.

In that case, I would put in a quart of Lucas oil additive, a quart of Risolene engine oil treatment and then depending on the climate and temperatures you expect to see on your trip I would top it off with either 20W-50 or straight 40 weight Exxon or Quaker state oil. Then I would open her up on the highway and then retest it after your round trip. Since you already used seafoam on the fuel system the injectors, etc are probably as clean as a fuel treatment is going to get them. Sometimes piston rings can do weird things and then undo themselves with the right oil additives and a litlle highway run in. Don't forget to change the oil filter too.

Have you tried disconnecting the electrical connection on each fuel injector one at a time to see how that affects engine performance and the exhaust?

Since the pressure was in spec after adding the oil, I would suspect an excess fuel feed washing the oil off the piston rings, etc. To me the plugs look like it is running way to rich on several cylinders. I have seen plugs much worse than those that were oil soaked, wet, solved with 40 weight oil and slightly hotter plugs. Of course in those days we did not need to pass emissions tests, so that may not help.

If I am right I would just pray that the seafoam lossened up the injectors so they reseal properly until you get back from the holidays.

Good Luck!

Mike McGinness
South Houston, TX

Ecomike said:

Since the pressure was in spec after adding the oil, I would suspect an excess fuel feed washing the oil off the piston rings, etc. To me the plugs look like it is running way to rich on several cylinders. I have seen plugs much worse than those that were oil soaked, wet, solved with 40 weight oil and slightly hotter plugs. Of course in those days we did not need to pass emissions tests, so that may not help.

Click to expand...

I have always noticed that the fuel pump seems to run way too hard. I don't have any method by which to verify that though. It's just loud as hell, especially without any carpet now. I've got to pick up a caliper to replace one that is seized, I might grab a fuel pressure gauge while I'm at the store.

It's already dropped a few quarts driving around town since the oil change. I'm putting a quart in it each night. I guess the 10W40 isn't heavy enough to stay. Not a surprise there. I'm also going to grab some straight 40 weight and perhaps another oil additive. I'm going to do some research today to see if there's much info about the best additive for ring blowby. Might go with the Rislone.

If the fuel pressure comes back too high at the rail... is it narrowed down to the FPR and the fuel pump then? How would I narrow it further down that line. Thanks.

Do you have alot of oil in your airbox?

1985xjlaredo said:

Do you have alot of oil in your airbox?

Click to expand...

Not yet. The FAI return hose has only been hooked up for a couple of days though. It has been blowing even more smoke out of the tailpipe ever since I hooked it up. I just don't think that it's had time to really show up on the brand new filter yet.

Concerning Additives:

I think I'm going to give "Restore" a try to start. I've read some interesting info on its' claims to fill scratches or scoring on cylinder walls, and some tests seem to show it working to reduce the resulting blowby. I'll probably grab a bottle or two of other smoke/blowby treatments, as well as some considerably thicker oil. Maybe straight 30 or 40. Losing oil like it is, I'm going to be in a delicate balance of oil and additives remaining in the engine. I just need it to hold together through this weekend, and preferably for another month or two. I know that a replacement engine is in my near future. More likely a replacement car, given the crazy amount of neglect that this thing has seen.

I'll certainly report back on how the "Restore" seems to effect the smoke/blowby problem. In conjunction with some heavier oil, I'll be interested to see what kind of compression numbers I'm getting after I run 400+ miles on it this weekend.

Down here in Houston I have run straight 40 wt, and 20W-50 wt with a quart of Lucas oil add. and a quart of either risoline or marvel mystery oil on old well worn engines. Got nearly 450,000 miles out of a 78 gas Dodge 360-V8 once.

I have heard from engine rebuilders that piston rings can temporarily, on very rare occasions line up in a row on the gaps and throw or burn lots of oil for a short while. I would be real careful with additives that put coatings, especially teflon (flourinated) coatings as the combustion products produce HF acid (hydroflouric acid - Really nasty stuff) that can do more harm than good.

Mike McGinness
South Houston, TX