when I took

[navi tasan]

1-They arrived when I took my shower.
2-They arrived while I took my shower.
3-They arrived when I was taking my shower.

In which case:
a-They arrived after I finished taking my shower.
in which
b-They arrived while I was taking my shower.
and in which
c-They arrived when I started taking my shower.

I think:
4-He left when I signed the papers.
means he left after I signed the papers, but I think here we have a cause and effect relationship which does not exist in 1.

Gratefully,
Navi.

[5jj]

1-They arrived when I took my shower.
2-They arrived while I took my shower.
3-They arrived when I was taking my shower.

4-He left when I signed the papers.

#1 is not natural English.
#2 is also not natural. It suggests that the acts of arriving and of taking the shower last the same amount of time.
#3 is fine with both 'when' and 'while. It means that they arrived after I had started taking my shower but before I had finished.
#4 is fine, though I feel that the past perfect 'had signed' is more natural. With the past simple, I feel a strong idea of cause and effect. This idea is not nearly so strong with the past perfect.

[navi tasan]

Thank you very much 5jj for all your replies.

Could I try a couple of more sentences without trying your patience?
Do these work:

5-Every day, the children arrived home from school when I took my shower.
6-He left when I took my shower.

I really don't see a significant difference between 1 and 6 and would assume that 6 is unnatural.
On the other hand, 5 expresses a habitual action. I am not entirely sure it belongs to the same category as 1.

Gratefully,
Navi.

[bhaisahab]

Thank you very much 5jj for all your replies.

Could I try a couple of more sentences without trying your patience?
Do these work:

5-Every day, the children arrived home from school when I took my shower.
6-He left when I took my shower.

I really don't see a significant difference between 1 and 6 and would assume that 6 is unnatural.
On the other hand, 5 expresses a habitual action. I am not entirely sure it belongs to the same category as 1.

Gratefully,
Navi.

5 is not natural English. It would be OK as "Every day, I took my shower when the children arrived..."