Crankshaft won't rotate more than 90*? (Timing Belt Replace)

[ED03GV_626]

what's up guys, so here's the issue. I'm replacing my timing belt, and everything was going smoothly until i had to rotate the crank while adjusting the tensioner.
i could no longer rotate the crankshaft more than 90-degrees in either direction, like at all. it jams to where I believe something may be out of line.

weird thing is the OEM timing belt marks are all aligned with the camshaft and crankshaft sprockets. what's causing this jam, and how can I fix it so I can freely turn the crankshaft and finish this job?

[itsa300zx]

Maybe remove all the spark plugs and try turning again. The compression on each cylinder will give you resistance.

[ED03GV_626]

yeah even with all the spark plugs removed, it still won't budge at all.
it's so hard to move that I either tighten the crank bolt all the way down to 160ft/lbs, or loosen the bolt completely without spinning the crank.

[itsa300zx]

Just to be sure, your shifter is in neutral??

[ED03GV_626]

lol, yeah it is. I was hoping that I left it in 5th, but no it was and still is in neutral.

[Z-owned]

I know you said the belt was lined up but it really sounds like your hitting valves with the pistons thus being unable to do a rotation.

[ED03GV_626]

any advice on how I can set all the valves to a closed position, that way I can reset the timing and have no contact? I just need to know where the cam sprockets usually face when all the valves are closed

[itsa300zx]

Be sure all the dimples on the cam gears are closely lined up with the dimples on the rear timing belt metal covers (this ensure TDC for cylinder 1). If not, you need to remove the belt and rotate each cam gear very slowly and controlled until they are in position. Reinstall TB with lines matched up with dimples on cam gears. As a double check, count the cogs of the TB according to the FSM.
Page em-18
http://www.texasnissans.com/fsm/300ZX/90_300ZX/em.pdf


I'm assuming you did not have the engine with the 1 cylinder at TDC when you removed the original belt.

[ED03GV_626]

yeah when the old belt was on, I was slowly rotating the crank by hand to align it at TDC. then, because of the worn belt, the teeth started coming off, and the crank sprocket didn't have enough teeth to catch and rotate all the gears. I had no choice but to remove the belt off-TDC and re-align from scratch.

after I aligned everything to TDC and installed the new belt, I got to where I had to rotate the crank to adjust the auto-tensioner. that's where I found that the crankshaft wouldn't rotate more than 30-degrees clock or counter clockwise.

[ThisIsSparTTa]

Yea, I'd make sure you have all the marks on the cams and sprockets lined up with the back of the covers, etc. You could also remove your belt again, and make sure each cam and the crank can spin a full 360 on its own just for a sanity check. Also, I wouldn't put 160lb's of force on the crank if its stuck. Sounds like most likely you're jamming some valves into your pistons, and you don't want to bend them.

[ED03GV_626]

this is just difficult because the crank won't rotate down to TDC, so I basically have to align the belt and sprockets offset of the back-covers.

so just to final-check... in my case, the dot on the crank gear won't go past, and is pointing at about 2:00, slightly above the oil pan notch.

this means that i will have to carefully rotate the cam-gears CCW, and align the belt and gear at a position that is slightly to the left of the valve resting position (away from where the back plate marks are) correct? to ensure that the pistons and valves are corresponding to the cranks current 2:00 position?