Rep Power: 0

So I took the manual transmission out of my 2000 Civic (1.6 SOHC) finally got it rebuilt with new sychros and a new 3-4 shift fork to fix grinding. I put the transmission back in, put the car back together, went to start it (it had sat for about a week) only to find out the engine refuses to turn over. I get a click and a hum from the starter, but no crank. I tried to push start it, but as soon as I engage the clutch, the front wheels lock up and it screeches to a halt. As far as I can tell, the transmission can't be the issue. The car will roll in in neutral, but the engine will not turn over even with the clutch disengaged.

I am confused as to what could cause that to happen. I already removed the spark plugs and attempted to turn it over (in case of a hydro-lock) but it made no difference. I don't believe the serpentine belt could have stood up to someone pulling my car to about 15mph and popping the clutch, like the belt would have either broken or just slipped around whatever pulley is seized, but maybe I am wrong? Umm...Seized water pump? Spun main bearing that finally "pressure welded" together? The engine ran perfectly prior to having the transmission out...

I don't have money for a new engine or even to take it to a shop right now, so I am really homing it's something fairly minor that I am just missing...

 
Rep Power: 518

I have witnessed a locked up accessory pulley cause the engine to appear seized up. Several times. Most recently a 3.5 liter honda engine .with a locked up compressor pulley.

Slipping the accessory belts off as a basic check is a valid and damn good idea
Can you rotate the crankshaft counterclockwise using a 19mm socket set or the bigass special wrench that fits the huge hex in the pulley?
How about trying to rotate it clockwise?
Did you lose any of the dowel pins (there should have been two) that go between the engine block and the trans bellhousing?
How many bolts actually hold the trans case to the engine block? 8 or 10 maybe? Loosen all of those bolts far enough to allow a decent gap between the block and the bellhousing, maybe something is in a bind. You're already in deep, the wrench work should still be fresh in your head so the work should go much quicker, and you should already have accepted that you might have to retrace your steps to find whatever went wrong, even if it means pulling the trans out again.

Did you replace the clutch too? Wait, it read as though that works ok.
Are you using 2nd or 3rd gear during the push start? Don't use 1st. The gear ratio just doesn't work well for push starts.

 
Rep Power: 0

Yes I have tried to turn the crank CCW with a 17mm socket (the one that fit the nut) and a large breaker bar, and It will not budge. I was using 2nd gear to push start. Could a locked up accessory pulley really cause the drive wheels to lock up and skid when put in gear? I did not think they were that strong.

 
Rep Power: 512

FWIW, I had my 2002's alternator pulley seize up on me out of nowhere and I couldn't rotate the engine via crank pulley bolt, nor could I push start it. Was fine in neutral, but once I popped the clutch, skidded to a halt.