Truck sat for some time (maybe a year or so) probably low on oil. It started, but I didn't run it very long. Did an oil change (and some other things) and now it won't turn over. I don't think there could have been too much damage done, but who knows. Any ideas on how to free it up again?

 

Well if it's truly seized then theres very little chance of getting it unseized. To double check and make sure it's seized, take a long breaker bar with a large socket (cant remember what size off hand) and just try to turn the crank back and forth by hand. If you can't then it's quite seized. You'll probably be in for a full rebuild if that's the case.

 

You can also try some marvel mystery oil or something thin in the spark plug holes. Let it sit a day and try with the breaker bar as Alex suggests. I had this happen to me three or four weeks ago and I hope yours turn out better than mine. Mine was screwed with a bent connecting rod and exploded piston. Also, try turning it with the spark plugs out and the belt off so any compression and tension won't be working against you. Try turning it backwards (counter clockwise facing the truck) first. If you end up loosening the crank bolt doing that it is bad news because that means it is locked up really bad.

What did it sound like when it was running?

 

The marvel or alternatively ATF is great for an engine that's been sitting for a long time and won't turn at all, but since his turned and started then it won't do anything. The reason those two work is because they break down rust rings in the bore that prevent the engine from turning.

Good points on all the rest though.

 

Do as Charlie says, remove the plugs, squirt some oil like maybe penetrating oil, give it time to soak the rings. Try cranking with starter and plugs removed, if not use the wrench method. On some vehicles, I could get to the teeth on the flywheel(had to remove the starter on a few) and use a large flat screwdriver and using the block as leverage, move the flywheel a small amount at a time. If you do remove the starter, gives you a chance to test it to see if it is ok. Starter should darn near jump across the floor from the torque.(if not secured.

 

if it started and ran then it couldn't be seized, have you tried hitting the starter a couple time with a hammer?
what do you mean it wont start? does it crank or spin over? does it cough and fart? or does it just go click.


I WILL THROW THIS OUT THERE FOR ANYONE WHO MAY BE DEALING WITH A SEIZED MOTOR IN THE FUTURE: may i make a similar suggesting fill the cylinders with diesel fuel and let it sit a week or so before trying to rock the engine, i have freed up many a motorcycle left out to the weather this way. The diesel fuel has always worked better that any type of oil for me.

 

It just clicks, but only once. Doesn't sound like a typical starter issue.

 

Still could be the starter with those symptoms. Smack on the starter a few times and give it a go. The only thing turning me away from the starter is that it was running and died.

 

so it ran you shut it off, changed the oil and it wont start? when did this happen?

 

It ran, changed the driveshaft and the oil, it ran again, I shut it off. Now it won't turn.

Thanks for all the suggestions!