there is something wrong

I have entered this code for Health

#pragma strict
var fullHealth = 300 ;
var curHealth = fullHealth;
static var lives = 3 ;

function Start () 
{
    print ("Health :" + curHealth) ;
}

function ezzayEsse77a (ozbot : int)
{
    if (curHealth >= 1)
    {
        curHealth = curHealth + ozbot ;
        print ("Health" + curHealth) ;
    }
    else
    {
        curHealth = 0 ;
        kill ();
    }
    
    if (curHealth > fullHealth)
    {
        curHealth = fullHealth ;
    }
    if (fullHealth < 1 )
    {
        fullHealth = 1 ;
    }
}

function onCollisionEnter (hit : Collision)
{
    if (hit.gameObject.tag == "Smallhit")
    {
        ezzayEsse77a (- 100);
    }
    else if (hit.gameObject.tag == "Bighit")
    {
        ezzayEsse77a  (- 200);
    }
    else if (hit.gameObject.tag == "Killerhit")
    {
        ezzayEsse77a (- 300);
    }
    else if (hit.gameObject.tag == "up100")
    {
        ezzayEsse77a (100);
    }
    else if (hit.gameObject.tag == "up200")
    {
        ezzayEsse77a (200);
    }
    else if (hit.gameObject.tag == "up300")
    {
        ezzayEsse77a (300);
    }
}

function kill ()
{
    if (lives > 0 )
    {
        lives -= 1 ;
        curHealth = fullHealth ;
    }
    else
    {
        lives = 0 ;
    }
    Debug.Log (lives);
}

and I have tagged the boom with Smallhit
but when the boom touch the car the Health doesn’t change
what is the wrong?

Case sensitivity matters. The method should be called OnCollisionEnter, not onCollisionEnter.