S40: 2003 S40 1.8s manual cambelt issues

[nokinnikon]

fitted cambelt, camshafts moved from 12 to ten when old belt released,
i then turned them back to the marks where i had set them.
fitted new belt, tensioner, pulley, set the tab in the middle with the 6mm allan key on tensioner and then tightened it up.
Then put it all back together, started it up ran like it was firing on 1 cylinder then shut down, started again a couple times more, same again. I then took spark plugs out no damage at all, put them back in turned the engine by crank pulley no horrible noises and rotation was as before i took old belt off,
then took timing case off belt seems really loose but timing marks still align. can anyone advise what i have done wrong here please, is there a remedy? is my engine a non interference or interference, all help would be greatly appreciated. for the record the nut on the crankcase pulley is jammed solid, so i took off the bottom guard and slipped the belt on that way. i couldnt check the crankcase alignment mark obviously but does'nt the crank alogn with the cam marks when i first set up the timing marks?

Jason