Ignition turns backwards but not forward

Hello, I would suggest to first try a different key - a worn key can sometimes prevent full ignition cylinder movement. You did not mention if it is a automatic or manual transmission equipped vehicle - Automatic has a shift lever interlock that could be in question; manual has that little tab by the cylinder that could be of concern. Since your key turns one way but not the other, I'd lean towards worn key or perhaps even a key cylinder issue internally. If an alternative key does not help, you may need to seek professional assistance at a shop near you. Use this link to find some shops near you that can help with your concern: www.repairpal.com/repair-shops