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  #76  
Old March 18th, 2020, 08:59
CJR CJR is offline
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Re: Cherokee XJ RENIX 1990 - low power, bad mpg, problem with ignition and timing

1990JeepXJ,

Your rings may be OK, but stuck closed in the piston grooves. Something inexpensive to try to free up the stuck piston rings. Pull the plugs and spray a whole can of Gumout equally in all cylinders. Let set overnight, replace plugs and fire it up. You'll get a little white smoke and it will clear up. The rings will now be free to work as they're supposed to work. The Gumout will drain into the crankcase and evaporate. This technique works the best for me as it puts 100% solvent on the rings and is better than some solvent added to the oil where it's diluted to 5% or 10% solvent strength before it gets to the rings.

Best regards,

CJR
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  #77  
Old March 21st, 2020, 11:28
szachmat szachmat is offline
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Re: Cherokee XJ RENIX 1990 - low power, bad mpg, problem with ignition and timing

Rockers, rods, lifters and valve head out of engine.
New photos here:
https://photos.app.goo.gl/bFvUHtGWvEhxvc368

The head gasket had black parts/spots mostly between cylinder 2-3 and 3-4.
I think the hone on the cylinders is ok, it's vissible and you can feel it under finger.
Push rods are worn out i'm sure. You can even see on a few that they are shorter than the others = rocker arms are worn out too.
The lifters have some cracks, and on most of them the edge is very sharp.
Pistons 1-4 looks nice for me, but 5 and 6 have some different, like they would burn oil?

Based on this I'm also 99% sure i need to replace my camshaft.
Do you guys see anything i missed?
Any suggestions?

Btw, do you think this is still original head gasket? Or was it replaced?
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  #78  
Old March 21st, 2020, 14:10
CJR CJR is offline
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Re: Cherokee XJ RENIX 1990 - low power, bad mpg, problem with ignition and timing

Good job on the photos. Not good on the cracked lifters. Cylinders look half decent. To me it looks good for a new cam, lifters, pushrods, and a new head gasket. You'll need to set the preload on the lifters properly and you should be good to go. This looks like a minimal rebuild to me. The head gasket needs to be installed correctly and I can offer some help there. Likewise, I'll give you the procedure for setting the lifter preload properly. You should have this engine running well in a short length of time. Also, while the head is off, spray GumOut into each cylinder to free any stuck-closed piston rings.

Best regards.

CJR
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  #79  
Old March 21st, 2020, 14:52
szachmat szachmat is offline
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Re: Cherokee XJ RENIX 1990 - low power, bad mpg, problem with ignition and timing

Quote:
Originally Posted by CJR View Post
To me it looks good for a new cam, lifters, pushrods, and a new head gasket.
What about rocker arms and head bolts? For bolts I have found 1 set in poland, but it looks different, and i'm not sure if it will fit.
Mine are for 6 point (hex) ~17mm socket.
The one i found are for 12 point 13mm socket.
https://www.usauta.pl/index.php?cPat...1301&pID=14707


Quote:
Originally Posted by CJR View Post
You'll need to set the preload on the lifters properly and you should be good to go. This looks like a minimal rebuild to me. The head gasket needs to be installed correctly and I can offer some help there. Likewise, I'll give you the procedure for setting the lifter preload properly.
Great
I'll let you know when I will get all the parts, and prepare my valve head.
I want to resurface it.

Quote:
Originally Posted by CJR View Post
Also, while the head is off, spray GumOut into each cylinder to free any stuck-closed piston rings.
What kind of product exactly?
I cannot buy any of gumout products in Poland.
I wanted to pour there engine flush or maybe a diesel fuel?

Btw, what can you say about new camshaft from CROWN automotive?
IF i will order parts in Poland i can choose only between NTY, and CROWN...
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  #80  
Old March 21st, 2020, 18:47
CJR CJR is offline
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Re: Cherokee XJ RENIX 1990 - low power, bad mpg, problem with ignition and timing

1. Rocker arms seem to last forever and are inexpensive. If you think you need new stock ones then get them. Likewise, replace the pushrods with the new cam and lifters.
2. I'd stay away from torque-to-yield head bolts that can only be used once and then must be discarded. Older XJs had reusable head bolts. ARP head bolts are excellent and reusable if you can get them over there.
3. GumOut is a carb cleaner which has two solvents; one for oil residues and one for lacquers which are present in gasoline. Check out carb cleaners available there and try them.
4. Definitely have the head resurfaced. If you remove the valves, before resurfacing, mark the valves/springs/keepers/locks for each cylinder and its valves. Likewise, hand-relap the valves to their seats. If you recut the head valve seats, locate the head seats close to the outer circumference of the valves. Reason? As the valves heat-up and expand in diameter the head's seat contact area, on the valve, will move inward towards the valve stem. If the head seat is cut too close to the inner diameter of the valve, the seat can move off the valve as the valve thermally expands and combustion gases will leak by the valve seats.
5. Typically, companies buy camshafts from cam grinders and rebrand them. I haven't used Crown cams but would expect them to be OK. I've only used Chevy, Crane, Comp, and Edelbrock cams and have had stock Jeep cams reground to custom durations and lifts.

Best regards,

CJR
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  #81  
Old April 2nd, 2020, 13:43
szachmat szachmat is offline
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Re: Cherokee XJ RENIX 1990 - low power, bad mpg, problem with ignition and timing

I'm still waiting for the autoparts from US, but i managed to take off oil pan and removed 1st piston to check how it looks.
I decided to change piston rod bearings, camshaft bearings and piston rings and hand hone cylinders.
Below you can see some new pictures, camshaft is damaged... and i'm worried about my cylinders... i have found rust on the 1st one, didnt check others yet. But now I need to rebuild it anyway.

https://photos.app.goo.gl/uGv878c61EQRT5nYA

Probably replacing cylinder sleeves without replacing pistonts is pointless... and it generates alot of work and cost... I think they need to stay.
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  #82  
Old April 3rd, 2020, 06:34
szachmat szachmat is offline
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Re: Cherokee XJ RENIX 1990 - low power, bad mpg, problem with ignition and timing

All pistons are out.
What worries me most is 5th piston rod, it looks very bad under bearing:

https://photos.app.goo.gl/u3cAZVdgg6htaaYz8
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  #83  
Old April 4th, 2020, 07:40
CJR CJR is offline
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Re: Cherokee XJ RENIX 1990 - low power, bad mpg, problem with ignition and timing

So far, things appear reasonable. Here's what you need to do;
1. Pull the crankshaft, and get some 800 grit or finer polishing cloth and then CAREFULLY hand-polish each bearing surface to remove the aluminium/copper smear coating ( i.e. from bearing). You want to get the cast-iron surfaces down to bare metal.
2. Now "mike" the OD of each bare crankshaft bearing surface at two(2) positions (90 degrees apart) and record the measurements for EACH bearing surface. Use a good micometer and NOT a vernier caliper. We are trying to determine if ALL bearing surfaces are close or whether one or more bearing surfaces were previously ground smaller and then fitted with a larger bearing.
3. It appears most of your oil-control rings( i.e. bottom rings) are locked- closed. Spray them with GumOut or equivalent to free them. Later, you'll need to inspect the the piston ring-groove surfaces to "touch them up".
4. Take the connecting-rods and manually clean/polish the cast-iron ID sufaces, bolt the caps back on and "mike" the ID of EACH connecting rod at two(2) places( 90 degrees apart) and record the measurements. Use a micrometer type measuring tool; i.e. snap/lock adjustable inside diameter tool + micrometer. DO NOT use a vernier caliper. What we are trying to determine here is that ALL inside diameters are close or whether some were previously enlarged. Oversized bearings can be used to match over-ground con-rods to a good crankshaft. If ALL con-rods are within spec,, order ALL NEW connecting rod BOLTS. Connecting-rod bolts are "reversed-cycled", therefore subject to "fatique-life" and REQUIRE changing since they are inexpensive.
5. Your typical SLIGHT score marks on the soft aluminium pistons show the results of oil-control piston rings being "stuck-closed" and the lateral force of the pistons against the cast-iron cylinder walls. These score marks are not really important. What is REALLY important is that the ring-groove surfaces in the pistons are in good shape; i.e. free of carbon and suraces smooth for sealing. These surfaces seal against the rings. Most likely the cylinder walls will clean-up nicely with a little manual cylinder honing.
6. Because of your fake oil concerns in your country, you NEED to buy the cam manufacturer's recommended additives to add to your oil for start-up to break-in the camshaft lobes/lifters and prevent "wiping/destroying" the new camshaft/lifters. When you "fire-up" the rebuilt engine, keep the RPMS at 1500-2000 RPM for about a half hour to 1 hr to insure cam/lifter break-in.
7. Also, your bearing "rub-marks" (i.e. wearing away of bearing layers) is typical of previous rebuilds where the engine rotating mass was not "rotationally balanced". Typically using heavier oils in unbalanced rebuilt engine will prolong engine life.

So far, in my view of your photos, a decent inexpensive rebuilt of your engine seems doable.

Best regards,

CJR
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  #84  
Old April 4th, 2020, 09:23
szachmat szachmat is offline
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Re: Cherokee XJ RENIX 1990 - low power, bad mpg, problem with ignition and timing

AD 3, 4. Piston rings will be new. I already have them. Pistons are cleaned. I tried to measure 5th connection rod and it seems it's not 'oval' but i used vernier caliper. I did all of this before I read your post

Last pack of photos, how camshaft looks and what I found in oil drain tube.
https://photos.app.goo.gl/Y1y2Nd42ho27bVHU9

I want to check all oil drain channels somehow. I'm worried that some may be clogged..

AD 6. You think this oil will be good? I have watched JeepSolid on youtube, and he used this oil for his rebuilded engine.
AMSOIL 10W40 Premium Protection Motor Oil - based on description should be good i think?

I also want to use special assembling oil, while rebuilding.
Maybe Millers assembling lube? Or it isnt needed and i can use just normal oil and then turn the oil pump few times before 1st start?

7. You suggest that this engine was 'rebuilded' before?
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  #85  
Old April 4th, 2020, 14:34
CJR CJR is offline
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Re: Cherokee XJ RENIX 1990 - low power, bad mpg, problem with ignition and timing

1. As I mentioned awhile back, I suspected your camshaft was bad and recommended that the lobe lifts be checked. Your recent photos, of the cam lobes, clearly shows badly worn cam lobes and bad lifters.
2. The oil drain-back holes, in the engine block, can easily be manually opened with aluminium rods.
3. Oil? Years ago, In the USA, our EPA removed the important friction additives from oils to save the "environment". Before the EPA ruling, you could use typical oils to break-in new cams. After the EPA ruling, many rebuilt engines failed during start-ups. Ask me how I know. Assume the European oil companies removed the same friction additives to "save money/increase profit margins". Bottom-line, you NEED the cam manufacturer's recommended additives to ADD to your engine oil before you start it up.
4. Use a good coating of assembly grease (moly.lithium, etc.) and NOT oil.
5. Prime engine with oil using the engine's oil pump and an electric drill with a screwdriver bit to fit into the oil pump slot that the distributor shaft drops into. Prime until oil floods into the head.
6. Previous rebuilt engine? Since you bought this car used, you don't know what was done to it before you got it. That's why you need to measure everything!
7. Cleaning your pistons is the first step. The second step is to make sure the piston ring groove surfaces are not damaged. The new piston rings need to seal against the sides of the ring grooves. Sometimes a very light cut or running a file around the ring grooves may be all that is necessary to refresh the sealing surfaces. For badly damaged grooves, the grooves may require re-grooving and the use of ring spacers in the grooves with the new piston rings.

Best regards,

CJR
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  #86  
Old April 7th, 2020, 01:07
szachmat szachmat is offline
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Re: Cherokee XJ RENIX 1990 - low power, bad mpg, problem with ignition and timing

Any suggestions for a good method for changing camshaft bearings without special tool?
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  #87  
Old April 7th, 2020, 07:00
CJR CJR is offline
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Re: Cherokee XJ RENIX 1990 - low power, bad mpg, problem with ignition and timing

Nope, but cam bearing insert/removal tools are easy to make if you have access to a lathe.

You need to make a tool from steel that consists of two pieces; a round stepped-disc and a long cylindrical rod.

DISC
Make a simple stepped-disc, with two diameters, out of steel. Make the steel disc about 1" thick, having a MAXIMUM shoulder diameter to just fit inside the bored diameter in the cast iron engine block. The second diameter on the disc should be lathe-turned in just fit the ID of a new bearing. The THICKNESS of the maximum diameter shoulder should be about 0.25". This shoulder will rest against one side of the installed bearing and clear the bored bearing holes in the engine block. Likewise, the disc should then have a central hole of about a 0.5" D. Remove all sharp edges/burrs.

ROD
The second piece needed will be a steel cylindrical rod (about 0.75"D -1"D) and about 3 ft. long. One end of the rod needs to be lathe-turned to fit into the central 0.5"D hole in the disc and it should be machined for about 1" long. Remove all sharp edges/burrs.

This tool will now remove the OLD bearings and also install the NEW bearings. When installing the new bearings, MAKE SURE THE HOLES IN THE BEARINGS ARE ALIGNED WITH THE OIL SUPPLY HOLES DRILLED IN THE CAST IRON ENGINE BLOCK! Covering the oil-supply in the block will starve the cam bearings of oil and "wipe" the new cam. Carefully tap each bearing into place, first starting with the rear engine bearing and ending with the front bearing.

Take your time and enjoy the install!

Best regards,

CJR
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  #88  
Old April 7th, 2020, 12:54
CJR CJR is offline
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Re: Cherokee XJ RENIX 1990 - low power, bad mpg, problem with ignition and timing

Addenda to my post #87.

The smaller diameter on the stepped disc, for cam bearing removal/insertion, should be EQUAL to the ODs of the journal bearings on the camshaft. That allows easy removal of disc from bearing after insertion.

Best regards,

CJR
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  #89  
Old April 20th, 2020, 01:58
szachmat szachmat is offline
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Re: Cherokee XJ RENIX 1990 - low power, bad mpg, problem with ignition and timing

Engine is finished and it's running well.
I did not measure the crankshaft with micrometer.
Due to coronavirus we had almost no customers in april I just had to cut the costs. I had to rebuild it as it is anyway, have no money for new crankshaft or buying bearings once more. I'm doing like 3-5tkm a year so I don't need this engine to last for another 100k.
Cylinder head was very 'curvy' and the exhaust valves were corroded. Guy who was fixing it told me that there was no way that it kept the pressure. But I really did check the compression and it had like it should.
Can't tell for now if the power is back or the mpg is better as I can't drive too much and i'm trying to stay on 2-3k rpm range, but as for now i don't feel any difference. At least there is no misfire at iddle when it's hot.


I would also thank to all who were involved in this topic and helped me alot with engine rebuild.
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  #90  
Old May 25th, 2020, 06:15
szachmat szachmat is offline
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Re: Cherokee XJ RENIX 1990 - low power, bad mpg, problem with ignition and timing

Just wanted to inform that it maybe has a bit more power in mid range, no max power increase, mpg is the same. No improvement.
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