I am tring to replace the rear main seal in my 1998 Dodge Ram 1500 and apon putting it back together I found that the crankshaft would only turn about 1/2 a turn. Iv'e tried everything that I could think of.
Do you hear or feel something banging solidly to a stop or does it just get tighter and tighter as you turn it? Did you have the bolts out between the flex plate and torque converter? One of them could be backed out and hitting on the rear edge of the block.
If it justs get gradually tighter, you're probably coming up on the compression stroke for one of the cylinders. You'll definitely feel that by hand but it won't bother the starter.
If nothing is obvious, you'll have to start removing parts again until the obstruction is found. That just means the pan and rear cap. Some people remove all the main caps thinking they can lower the crankshaft to get the upper part of the seal out. That only works if the flex plate is unbolted from the torque converter. If you did that, I bet you're going to find one of the caps is reinstalled backwards. Usually they won't even go back on backwards, but depending on how close it is, it might be possible to turn the crank a little before it gets tight. If you only had the rear cap off, obviously that one can't be turned around.