I heard a loud cluck when switching on and off the car

[nairv]

there is a very loud cluck when switching the car on and off. What is broken that i want to know please.

[Nehmaiz]

Is your A/C on when you turn on the car?

turn off the A/C then test again, might be the A/C compressor or A/C clutch making that sound.

would also help to know what year model we're talking about.

[Renier Venter]

There might be chicken stuck under your gas pedal...

[techy]

Lol. Could be anything. Maybe fuel pump.

[naveedr]

you must have broken something.