Muddz

If it's been sitting that long give it a while longer to see if everything will loosen up. Rusted parts can take a while to neutralize rust if your not using an actual rust remover of some kind. Most likely a much longer time duration using an ATF/acetone or similar type of mixture. The 4.0L uses a cast iron block, so trying to clean up a cast iron block will likely take longer than an alum. block.

Corrosion of the engine and engine oil are caused by dirt and moisture. If you happen to have a bypass filter it will clean the motor oil removing dirt, rust, corrosion and all of the water/moisture in the oil. Full flow filters work with volumes of oil, however the end result is the motor oil will be much dirtier with more moisture/water even if you change engine oil every 3k.

Dirtier oil creates varnish. Bypass filters also help to remove and reduce varnish buildup.

So if your running cleaner oil (preferably a synthetic with more detergents) and removing dirt, varnish, corrosion and contamination from the oil possibly could further help regain cylinder compression? It just may take up to a few weeks for the engine to become cleaner.

If the engine won't cleanup after a while removing rust, oxidation, varnish, etc. producing better compression. May be simpler to replace the engine block or perform an partial rebuild of the upper half of the block, hone cylinders replace rings, possibly pistons and other worn parts of the upper half of the engine block. Possibly including the cylinder head.

Idunno

Dumb question. If fuel is on the rail but the engine isn't catching, could the injectors be clogged? Is there evidence of raw fuel delivery to the cylinders? Methanol can gum things up pretty good in an engine fuel system that hasn't been cleaned out for long term storage.

Garrett S.

You might try some ether. It might have trouble catching on just gas and if you can get it to fire off once or twice it might run.

steelybill

I use Marvel Mystery oil in these situations. Pour some in each cylinder & let it sit for a week or two...stuck rings don't get unstuck over night...

cruiser54

True.