We removed our chain tensioner to replace after the mechanic told us that it needed changing due a rattling noise on start-up. when we looked at the old tensioner on the engine we noticed that the plunger had travelled past the sealing o-ring. we concluded that the chain ass. should be changed as well. We tried putting the engine on timing marks so we could remove the chain and install a new one with no problems (our first time doing the Nissan) but we were not aware that the chain would slip because of no oil pressure. We are now searching for assistance to align the crank and cam shafts correctly to reinsatll our new chain. Thanks for help.