engine half turn stop

[cybrstar]

I am trying to diagnose my spare engine before I start tearing into it. I have not encountered this situation before. I turn the crank shaft 1/2 turn and it stops. Seems like a valve is preventing the engine from turning over. And when I turn it the other way, counter turn, when stop it will turn again until it stops again. I know it maybe either the timing chain (skipped or snapped) and or valve hitting the top of the piston.... but has anyone encountered this before I start going into the motor? 1994 1FZ-FE.
Edit to correction of engine.

 

[flintknapper]

I am trying to diagnose my spare engine before I start tearing into it. I have not encountered this situation before. I turn the crank shaft 1/2 turn and it stops. Seems like a valve is preventing the engine from turning over. And when I turn it the other way, counter turn, when stop it will turn again until it stops again. I know it maybe either the timing chain (skipped or snapped) and or valve hitting the top of the piston.... but has anyone encountered this before I start going into the motor? 1994 1hzfe.

Do you have it on an engine stand and is the feeling when it stops turning one of something 'mechanical' (dead, hard, stop). Spark plugs removed from cylinders?

 

[inkpot]

We had a customer whose engine turned over freely, but there was nearly no compression in any cylinder. We figured it was a broke timing chain, but we were wrong, kinda. It turned out that the keyway that holds the cam gear on the end of the cam had shattered the cam gear. It was missing a whole spoke and several teeth. The rest of the teeth on the gear were damaged or missing. The timing chain failed instantly and fell loose in the bottom of the timing chain cover. If the cam or cam drive gear are damaged/broken it might cause a jamb in either direction. Pull the valve cover and take a look. John

 

[cybrstar]

Do you have it on an engine stand and is the feeling when it stops turning one of something 'mechanical' (dead, hard, stop). Spark plugs removed from cylinders?

Spark plugs are removed. Pistons look like they are moving. Not on an engine stand.

 

[flintknapper]

Spark plugs are removed. Pistons look like they are moving. Not on an engine stand.

So.....you're not running up against simple compression. It's mechanical then. Time to dig into it.

 

[BILT4ME]

You stated 1HZ-FE in the beginning, then you said the spark plugs are removed.

A 1HZ-FE doesn't have spark plugs.

 

[cybrstar]

Oops. Mean 1FZ-FE. Will correct on the original post.