Chris Brown Gangster Fail

Chris Brown suffered the ultimate vehicular humiliation Thursday ... as he tried to act super-cool in a classic whip that couldn't get off the dime.

A full crew and huge crowd gathered as Brown prepared to shoot his music video ... the singer cruising down Figueroa in L.A. in a super-sweet '60 Chevy Impala.

The engine repeatedly turned over but there was no ignition, as a clearly embarrassed Brown stoically turned the key ... with rapper Compton Menace riding shotgun.

That Lowrider said "I don't work for fake gangsters"

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