past instead of past perfect

[Navi]

Can one use:

1-Yesterday when we tested the computers and one of them malfunctioned. But he tried to sell the computer that malfunctioned.
instead of:
2-Yesterday when we tested the computers and one of them malfunctioned. But he tried to sell the computer that had malfunctioned.
Can one use:
3-There was an explosion and some of the windows cracked. I touched a window that cracked.
instead of:
4-There was an explosion and some of the windows cracked. I touched a window that had cracked.

[Mister Micawber]

Your first pair are only sentence fragments. Use 4 not 3.
_________________
Native English teacher at Mister Micawber's

[Navi]

Thank you Mister Micawber,

I am sorry. I put an extra "and" in those sentences, making them meaningless.

They were supposed to be:

1-Yesterday when we tested the computers one of them malfunctioned. But he tried to sell the computer that malfunctioned.

2-Yesterday when we tested the computers one of them malfunctioned. But he tried to sell the computer that had malfunctioned.

[Mister Micawber]

Unlike with 3 and 4, both 1 and 2 are clear.
_________________
Native English teacher at Mister Micawber's

[W]

Do both sentences 1 and 2 need commas between "computers" and "one"?

[Mister Micawber]

Strictly, yes; practically, no.
_________________
Native English teacher at Mister Micawber's