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Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go hereXJ (84-01)
All OEM related XJ specific tech. Examples, no start, general maintenance or anything that's stock.
As we have probably all have been told, "you just cant kill the 4.0." The 4.0 is known to be a fairly idiot proof engine where some have locked up and then a couple hours later, released and cranked right over again, or how they have ran with a window in the block for the up close and personal view of the internals doing their thing.
Well today my co-worker finally towed in his 1994 Cherokee that has been sitting for years due to the P.O. neglecting it and leaving it in a non running state claiming that it just needed a tune-up. Pushed the jeep in and started doing some long needed maintenance, oil change, plugs, wires, etc.. while i had the plugs out performed a quick compression test, Cylinder one netted me a whopping 15PSI of compression. Cylinder 2 and 3 were not far behind coming in at 35psi. threw some oil in there to check the rings and all compression raised to be above 100psi, Still not very good compression but at least it tells me, the Rings are SHOT.
I guess what I'm getting at with all this rambling, what would you guys do if this was your Cherokee, pull this engine and rebuild it? Junkyard motor? New long block all together?
We work for Chrysler so most parts are obtainable to us brand new.
I guess I'm optimistic, but I say put some Marvel Mystery Oil in the cylinders, roll it over and let it set a few days, fire it off and see what happens.
I agree! you stated it sat for several years and after that long things will for lack of a better word become lazy / stuck I would fire it up and let it run for a while put some sea foam in all things gas oil and go from there!
If it sat that long there's a chance the rings are locked into the piston grooves with corrosion and the MMO may loosen them up. If it doesn't try ATF and acetone 50/50 mix and wheel it over, then let it sit. The valves may be sticking in the guides as well.
I agree about using Marvel Mystery oil in it. It may not work overnight though. Putting a pint in the oil change may do some good, as it's driven, loosening the varnish & carbon etc in the rings... Some airplane folks us it at every oil change, even though it's really not approved by the Feds...
Well, an update.
Got to the shop yesterday morning and tried to give her a spin, no luck. As you mentioned Dave, i put a shot of ATF "combo" in it and spun it over a few times by hand to try and work it in. its now been sitting all day today and the night before. tomorrorw when i get some free time from normal shop work gonna go give it a try again.
From what i can tell from my tear down time on Saturday, everything under the valve cover seems to be moving as designed, all the push rods feel straight and i do get oil to the top of it.
Any other suggestions if the ATF/acetone combo doesnt work?
Have a short block im gonna pull out of storage and offer it to him and see what he says.
Well, an update.
Got to the shop yesterday morning and tried to give her a spin, no luck. As you mentioned Dave, i put a shot of ATF "combo" in it and spun it over a few times by hand to try and work it in. its now been sitting all day today and the night before. tomorrorw when i get some free time from normal shop work gonna go give it a try again.
From what i can tell from my tear down time on Saturday, everything under the valve cover seems to be moving as designed, all the push rods feel straight and i do get oil to the top of it.
Any other suggestions if the ATF/acetone combo doesnt work?
Have a short block im gonna pull out of storage and offer it to him and see what he says.
My dad had a 94 and put 400k on it before retiring it due to rust. The engine still ran perfectly.
If you can't get the original engine up and running - and the body of the Jeep is in good condition and not rusted out, I'd put a new engine in it - especially if you've got a "known good" one that has been properly stored.
I have tried to start it, after the oil combo sat and cranked the motor over with a momentary switch i have to blow any excess fluid out, and ran a compression test, did not have any gain in compression, regardless, tried to start it and it just sounds like it has a dead hole and will not fire over, im getting fuel spark and air. so compression is the only thing failing here.
Got ahold of the previous owner and he had it sit for nearly two years, then the current owner has owned it and it has been sitting for two years while in his possession.
My dad had a 94 and put 400k on it before retiring it due to rust. The engine still ran perfectly.
If you can't get the original engine up and running - and the body of the Jeep is in good condition and not rusted out, I'd put a new engine in it - especially if you've got a "known good" one that has been properly stored.
PatHenry, post renix, what would that make it, while it is still OBD1? please excuse my ignorance
11-18-2018, 12:30 AM
The 4Liter That Died..
Cylinder 2 and 3 were not far behind coming in at 35psi. threw some oil in there to check the rings and all compression raised to be above 100psi, Still not very good compression but at least it tells me, the Rings are SHOT. 
