1)When the phone rang,I had been washing the dishes 2)when the phone rang,I was washing the dishes
1) When the phone rang, I had been washing the dishes
You washed the dishes, then stopped, then the phone rang.
The PAST PERFECT PROGRESSIVE TENSE indicates a continuous action that was completed at some point in the past. This tense is formed with the modal "HAD" plus "BEEN," plus the present participle of the verb (with an -ing ending): "I had been working in the garden all morning."
2) when the phone rang, I was washing the dishes
You washed the dishes, while you were doing that, the phone rang.
We often use the past continuous and the past simple tense together to describe an action interrupted by an event. When this happens, the past continuous describes a longer, ‘background’ action or situation and the past simple describes the action or events.
I was playing a computer game when the doorbell rang.