I agree to what the above said about the whole being abandoned once thing. Especially chihuahuas and other breeds whose main purpose of being bred is as a companion. Which is why it is hard for them to be alone or have the possibility of being alone.
I would suggest using the good old method of leaving the room with small intervals. Start with 5 seconds, 10 seconds, 30 seconds...etc...it's really tiring on the human to walk in and out of the room but if it's the only thing left to try, you may as well right?
When I first got my chi and she cried her lungs at night when we slept and we ignored her. When we left the house we didn't make a fuss, just our usual walking about and we didn't even say bye. She cried a lot at first also but she eventually realized that no one is actually there to hear her...
I think the more she loved her crate and didn't mind being in it, the less she cried also for us. We never had any problems to be frank. We just let her cry when ever and we didn't do anything special. I put tons of toys in there, and every time she goes in her crate I feed her a treat. When I come home I put down my stuff quietly and slowly give her attention and eventually let her out.
Ray just needs to be confident that you WILL be back! If you are confining him while nobody is home, just make sure he loves his space to death. Haru climbs in her crate sometimes even when I let her walk around, she goes in there when she knows she is in trouble, it's her #1 comfort zone.