I think engine is toast?

[Jeff Kavanagh]

It's the AMC 258 i6 / 4.2l straight 6.
This jeep is out of an old damp equipment shed where it sat for around 5 or so years. When I first got it home it would not crank over by hand.
I pulled the plugs and put a Crown penetrating oil into it.
Slowly I worked a pry bar on the fly wheel back and forth and the engine came free. Free enough that a simple turn on the fan belt would turn it.
Did some other work with the ignition system (new solenoid, starter, etc., got it turning over with the plugs still out.
Next put new plugs in it and turned it over by putting gas in the carb.
Today I started it and it ran for around 5 seconds and then ceased right up. It won't even turn over with the pry bar. The oil level and all was good too before I did all of this.
I'm guessing the engine is done?

Jeff

 

[Lumpy Grits]

Sounds like the oil pump wasn't pumping.
LG

 

[Jeff Kavanagh]

I know it is a dumb question because it likely is impossible to know but I am guessing it's not a rebuild but time to find another engine?
I have a V8 in the other Jeep but am not sure how good it is.
I was worried about it because it has been sitting for so long.

 

[Lumpy Grits]

Only know for sure after a complete tear-down is done.
I have seen many seized engines rebuilt.
LG

 

[Jeff Kavanagh]

Thanks

 

[Peanut Butter]

It's the AMC 258 i6 / 4.2l straight 6.
This jeep is out of an old damp equipment shed where it sat for around 5 or so years. When I first got it home it would not crank over by hand.
I pulled the plugs and put a Crown penetrating oil into it.

Jeff

So what does this tell you? It tells me that there was enough rust in the cylinders to keep the pistons from moving up and down. Could even be that the rings were rusted to the cylinder. The fact that it now doesn't run doesn't surprise me. What you did only works on very mildly rusted parts. My guess is the rings are messed up. The AMC 258 i6 / 4.2l is a fairly easy rebuild compared to the V8. I'd pull it apart, see what was really wrong, and then rebuild the engine. If you search the Power Nation shows you'll find several rebuilds to include a 4.0L. If you don't feel comfortable doing this, pull it apart and see if you need a replacement short block or long block. The only other choice you have is to go buy a used running engine from a junked vehicle. Lots of choices, depends on your comfort level.